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Jiilich Nuclear, Research Center
—V- ~~ for the
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U.S. Environmental Protection Agency and
German Ministry of Research and Technology
Cause-Effect Research in the
United States of North America and
Federal Republic of Germany
-------
Cause-Effect Research in the
United States of North America and
Federal Republic of Germany
Forest Decline
A Documentation by
B. Krahl-Urban, H.E. Papke, K. Peters und Chr. Schimansky
with the Co-Operation of
D.A. Bennett • C.J. Brandt ¦ R.I. Bruck • E. Cowling ¦ F. Fuhr
A.H. Johnson • K. Kreutzer ¦ S.E. Lindberg
E. Matzner • S.B. McLaughlin • B. Prinz ¦ K.E. Rehfuess • F.G. Schroeder
P. Schutt ¦ B. Ulrich ¦ W. Zech ¦ H.W. Zottl et al.
Published by the
Assessment Group for Biology, Ecology and Energy
of the Jiilich Nuclear Research Center
for the
U.S. Environmental Protection Agency and
German Ministry of Research and Technology
-------
The discussion of forest decline has reached uncommonly large proportions in the
media as well as within the scientific community. For this reason, the publishers asked
the scientists who participated in the American German exchange to compile a
documentation of one of the most significant environmental problems, ft was anticipated
that this will provide a basis for discussion among the public, politicians and scientists.
This work was only made possible by the support provided by the authors and their
research institutes, for which the editors feet obliged to extend their special thanks.
During the excursions, the problems were discussed on site and also documented by
outstanding photographs. In particular, the editors would like to acknowledge their
thanks to all the forestry officials and park rangers, because without their help many
important photographs would not have been possible. German and American
colleagues contributed equally in drawing up the individual articles. The preparation of
the German and English versions resulted in a genuine German American cooperation.
The help of all those employees from the Julich Nuclear Research Center, too numer-
ous to name, who contributed to the technical setup is gratefully acknowledged.
Special thanks are also extended to Heiga Bongartz, Annehese Conrad- W/enands and
Carmen Telemann, who arranged the manuscript with great care. The inexhaustible
assistance provided by the central type setting department along with Horst Peter Petzer,
who was responsible for the entire photocomposition must be emphasized. Valuable
aid was also supplied by Rosel Sch/eren, who has taken a tot of trouble in the finishing
of the color enlargements. Karl Peters's former fellow-students from the Folkwangschule
in Essen, Norbert Denket and Konrad Haniscti, as well as Horst-Peter Petzer contributed
to the arrangement of text and pictures.
Finally, the editors wish to extend their thanks to the printer and lithographer, who were
successful in doing the brilliant color reproductions.
This documentation is available from:
U.S.and Canada:
US Environmental Protection Agency
Environmental Research Laboratory
Attn.: Dr. C.J Brandt
200 SW 35th Street
Corvallis, Oregon 97333
USA
Europe and other:
KFA Julich GmbH
Public Relations Department
Attn.: Dr. B. Krahl Urban
P.O. Box 1913
D -5170 Julich
Federal Republic of Germany
Publishers:
Editors:
Photography:
Graphics:
Set:
Page Make-Up:
Lithography
Printing:
© 1988 by KFA Julich GmbH
ISBN: 3-89336-006-9
Assessment Group of Biology, Ecology and Energy
of the Julich Nuclear Research Center
for the U.S. Environmental Protection Agency
and the German Ministry of Research and Technology
Dr. Bernhard Krahl-Urban, Julich, FRG
Dr. C. Jeffrey Brandt, Corvallis, OR, USA
Dr Christoph Schimansky, Julich, FRG
Dipl. Designer Karl Peters (Layout), Julich, FRG
Roger Peniston-Bird, Vienna, Austria
Dipl. Phys. Armin Benz, Julich, FRG
Jeanne Anderer, Vienna, Austria
Vera Stocker, Julich, FRG
Karl Peters
Hans W Schiffer, Julich, FRG
Eva Heuter, Duren, FRG
Graphics Department of Julich Nuclear Research Center
Manfred Platzbecker, Linnich, FRG
Reprotechnik Mirgel & Schneider GmbH, Bonn, FRG
Grafische Werkstatt Druckerei Gebr. Kopp OHG, Koln, FRG
-------
Contents
Prefaces 4
Scientific Excursions to German and
American Forest Decline Study Regions
B. Krahl-Urban and H.E. Papke 6
The Forest - an Ecosystem at Risk
H.E. Papke and B. Krahl-Urban 16
Cause-Effect Research of Forest Decline
Major Research Efforts in the
Federal Republic of Germany
and Eastern United States of America 36
Soiling
B. Ulrich and E. Matzner 42
Research Sites in the Soiling Area
B. Ulrich and E. Matzner 44
Hils and Eggegebirge
B. Ulrich, J. Gehrmann, B. Prinz
and G. Spelsberg 48
Research Sites in the Hils Mountains
B. Ulrich, G. Wiedey and J. Gehrmann 50
Preul3ischer Velmerstot (Eggegebirge)
B. Prinz and G.H.M. Krause 56
Harz
M. Hauhs, P. Benecke and B. Ulrich 58
Lange Bramke Catchment
M. Hauhs and B. Ulrich 60
Fichtelgebirge
W.Zech 64
Oberwarmensteinach, Wulfersreuth and Selb
W. Zech, R. Horn, M. Kaupenjohann
and R. Hantschel 66
Bavarian Forest
K. Kreutzer 70
Luchsplatzl
K.E. RcMucss 72
Steinhiittel
K.E. Rehfuess 76
The Munich Gravel Plain
K. Kreutzer 78
Hohenkirchner Forst
K.E. Rehfuess 80
Calcareous Alps
K. Kreutzer 82
Elendalm
K.E. Rehfuess 84
Black Forest
H. W. Zottl 88
Kalbelescheuer (Southern Black Forest)
H. // Zottl and E. Mies 90
Freudenstadt (Northern Black Forest)
H. W. Zottl and E. Aldinger 93
RoBberg (Northern Black Forest)
H. W. Zottl and E. Aldinger 95
Northern Appalachians
E.G. Schroeder 98
Camels Hump (Green Mountains)
A.H.Johnson 100
Whiteface Mountain (Adirondacks)
A.H.Johnson 104
/ Southern Appalachians
v F. G. Schroeder 106
. Mount Mitchell
1/7 R.I. Bruck 108
, ORNL Studies on Forest Decline
^ S B. McLaughlin 112
, Walker Branch Watershed (Tennessee)
^ S.E. Lindberg 114
Comparison of Damage Symptoms
in Central Europe and North America
H.E. Papke 116
Hypotheses
v/ to Explain Forest Decline
E. Cowling, B. Krahl-Urban
and Chr. Schimansky 120
Main Emphases of Research and
German-American Cooperation
H.E. Papke, B. Krahl-Urban
and Chr. Schimansky 126
Explanation of Technical Terms 128
Index 135
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Preface by the
Administrator
of the U.S.
Environmental
Protection Agency
This report describes the opening
of a new chapter in cooperative
environmental research between
the United States and the Federal
Republic of Germany. The impetus
for the activities described is a com-
mon concern in both countries about
unexplained ..declines" in certain
forests
The U.S. and the Federal Republic
of Germany have had a formal
cooperative agreement for environ-
mental research since 1974; one
has existed for agricultural and for-
estry research since 1981. In the
spirit of these agreements, repre-
sentatives of the two governments
undertook a project that allowed 22
scientists from the Federal Republic
of Germany, the United States, Ca-
nada and Belgium to spend two
weeks in the late spring of 1984 ob-
serving symptoms and debating
possible causes of decline in the
forests of Central Europe and east-
ern North America. The document
that follows is an outgrowth of these
visits.
In March of 1985, representatives of
the U.S. agencies involved in the
National Acid Precipitation Assess-
ment Program (NAPAP) met in Bonn
with representatives of the German
Federal Ministries responsible for
research in the fields of acid depo-
sition and air pollution. This meeting
Preface by the
German Minister
for Research
and Technology
Recently, according to the present
government agreement, expanded
cooperative work in forest decline
research was agreed upon by the
Federal Ministries active in this field
and their American counterpart
agencies. I am particularly pleased
with this agreement, because it is
expected that the associated close
exchange of information will activate
mutual stimulation of research ef-
forts in both countries.
This significant agreement was
reached through intensive discus-
sions held among scientists of both
countries and after joint excursions
through damaged forests both here
in the Federal Republic of Germany
and in the United States of America.
These contacts are documented in
great detail in this publication as the
beginning of cooperative efforts.
Today, in the Federal Republic of
Germany, more than half of the
entire forested areas are either da-
maged or diminished in vitality.
|| About 19 % of the forested areas re-
I'veals moderate to severe injury It is
now obvious that in many regions
environmental strain has led to visi-
ble damage of an important ecosys-
tem.
Since 1982, the Federal German
Ministry for Research and Technol-
ogy has set main emphasis on the
field of forest decline/air pollution
Preface by the
Assessment
Group for
Biology; Ecology
and Energy of
the Jiilich Nuclear
Research Center
In the past few years, the problem
of the novel type of forest damage
has mobilized the research commu-
nity, not only in institutes directly
concerned with forestry, and also
brought them together in investigat-
ing the causes. The Federal Repu-
blic of Germany and the United
States of America, two great indus-
trial nations, feel that they must also
share responsibility for reactions on
the part of the environment to de-
cades of environmental pollution by
anthropogenic sources. This also
explains the spontaneous readi-
ness of the two countries to partici-
pate in intensive cooperation.
In 1982, when I first contacted the
Environmental Protection Agency
(EPA) and in 1983 the Electric Pow-
er Research Institute (EPRI) in Palo
Alto, California, I was pleased to
find a great willingness on the part
of the scientists to develop these
contacts with the aim of exchanging
experience, of carrying out joint re-
search concepts and finally also of
realizing these programes on re-
search into the novel type of forest
damage. My thanks are due to the
Environmental Protection Agency
(EPA) and the Federal German Min-
istry of Research and Technology
for spontaneously providing the re-
sources for this scientific exchange.
Aside from the scientific discus-
sions held in the affected forest de-
cline areas personal contacts were
made possible and also intensified
as an important basis for a success-
ful future cooperation.
-------
identified further subjects of study
and areas of cooperation that parti-
cipants hoped would rapidly reduce
the great uncertainties in our under-
standing of the acid deposition phe-
nomenon and its effects.
Within the U.S. National Acid Pre-
cipitation Assessment Program, a
Forest Response Research Pro-
gram has emerged and rapidly
grown. Its mission is to explain pos-
sible air pollution-related causes of
changes in the structure, function
and composition of forest ecosys-
tems. The program's planning,
implementation and management is
the joint responsibility of the U.S.
Forest Service and the U.S. Envi-
ronmental Protection Agency. Re-
search on forest response has
grown from $1.2 million four years
' ago to $12 million today. These two
agencies have established Re-
search Cooperatives to study Ihe
major forests in the United States.
As a result, the dynamics of the
spruce/fir, southern commercial
pine, eastern mixed hardwood and
western forests should become
much better understood. In addi-
tion, the forest program is working
to improve our understanding of the
forest's atmospheric environment,
and to survey forests for change
and damage.
Given such careful planning and the
efforts of our two governments, and
particularly the scientists of both
countries, I look forward to rapid im-
provement in our understanding of
both forest declines and actions
which may be needed to foster and
preserve our nation's forest ecosys-
tems. This report is but one exam-
ple of valuable outcomes from inter-
national cooperative ventures.
Lee M. Thomas
and has also continously increased
a major portion of its efforts in the
field of forest decline/air pollution.
In 1986, more than 18 million Ger-
man Marks have been made avail-
able for research in this field. Re-
search efforts are geared to deter-
mine as precisely as possible all
hypotheses, influences and effects,
which have contributed to forest da-
mage and are presently still respon-
sible for this outcome. This knowl-
edge is necessary in order to com-
bat forest decline directly, in ad-
dition to controls on emissions al-
ready in effect as part of the preven-
tive environmental policy.
Since environmental research is a
major element of preventive envir-
onmental policy, it is important
to improve the requirements and
scope of the political decisions.
This is more easily accomplished
the closer the cooperation. On a na-
tional scale, the Federal Republic
has introduced a program to coordi-
nate the various research efforts on
cause and effects.
Due to the transboundary nature of
the problems of forest decline and
transport of air pollution - which
present available knowledge indi-
cates as one of the most important
causal agents in the complex of
cause-effect relationships involved
in forest decline - research also re-
quires cooperation on an interna-
tional scale. Only with a common
basis of understanding about the
causes and mechanisms of damage
it will be possible to convincingly
substantiate and politically motivate
the necessary efforts to reduce en-
vironmental impacts in all countries.
I am convinced that the best re-
quirements for a successful devel-
opment of this cooperative work
have been fulfilled on the basis of
established contacts and intensive
exchange of research results and
findings. In this way, new knowl-
edge and contributions towards the
recovery of forests are attainable.
Dr. Heinz Riesenhuber
Since 1978, the German Ministry of
Research and Technology has been
supporting work on research into
the influence of environmental
chemicals on terrestrial ecosys-
tems. Based on these studies in
spring 1983 comprehensive promo-
tional measures for research into
the causes of the novel forest de-
cline were converted into a concept,
which on a site basis primarily
brought together the various disci-
plines in acquiring data on damage,
in recording the reaction of trees
to stressors and in evolving the ana-
lysis of nutrient and pollutant bal-
ances in the forest ecosystem.
This is a major task which can, how-
ever, only achieve its goal in the
long term if an intensive coopera-
tion between the individual disci-
plines is taken into account along
with the complete incorporation of
all site factors in parallel to detailed
experiments under defined, repro-
ducible conditions.
The excursion in the Federal Repu-
blic led to the priority areas of this
research. The demonstrations on
site were the best way to show to
which extent damage is apparent to
soils and forest cultures, which find-
ings are already obtained in the
brief research span and which ob-
jectives are set for the next period
of research.
In this book, the most important re-
search sites in the Federal Republic
of Germany and eastern United
States are described where inter-
disciplinary research has been in-
itiated. Working hypothesis and re-
search approaches are presented
as well as first results. I personally
would like to thank the committed
research groups who considerably
assisted the Nuclear Research Cen-
ter Julich in the conception and edi-
tion of this book. This publication is
a contribution to the interim balance
of coordinated forest decline re-
search, which will further lead to
ecosystem research.
Prof. Fritz Fuhr
5
-------
Scientific Excursions
to German and American
Forest Decline Study Regions
B. Krahl-Urban and H.E. Papke, Julich Nuclear Research Center
Decline of forests has been report-
ed periodically in the past. Since
around 1975, a rapid development
and large extent of the novel forest
decline was observed in the Federal
Republic of Germany. Major increas-
es occurred from 1980 through
1982. The present decline situation
shows only limited agreement with
previous decline episodes. The new
decline symptoms include
• rapid development on individual
trees
• occurrence in different forest
types
• long duration (over more than
10 years)
• occurrence throughout the natu-
ral range of affected species.
Initial explanations ranged from ex-
clusive effects of natural stress fac-
tors to exclusive effects of anthro-
pogenic stress factors. Recent re-
search indicates that air pollution
plays an important role in the forest
decline syndrome. Because of this
connection to airborne pollutants
the phenomena of forest decline
has reached international attention
within the scientific community and
in the media.
In 1984, scientists from the United
States, the Federal Republic of Ger-
many, Canada, and Belgium made
tours of forest decline study regions
in the Federal Republic of Germany
and the eastern United States. At
each of the research sites visited, at
least one of the participating scien-
tists was involved in studies of
cause and effect relationships. The
goals of this exchange were to:
• reach a common understanding
of the visible decline symptoms
• exchange published and unpub-
lished data on sites, symptoms,
and pollutants
• discuss suggested hypotheses
• identify the most important gaps
in research.
The first American-German scientif-
ic exchange on research into the
causes of forest decline was sug-
gested by Professor Dr. Arthur
Johnson (University of Pennsylva-
nia) and Professor Dr. Fritz Fuhr
(Julich Nuclear Research Center).
The excursions were financed joint-
ly by the US Environmental Protec-
tion Agency and the German Feder-
al Ministry for Research and Tech-
nology.
The present documentation is in-
tended to shed light on this environ-
mental problem by presenting the
main hypotheses and the latest re-
sults from individual study sites.
The editors and authors of this re-
port recognize the need to inform
the public of the current state of re-
search into causes and effects of
forest decline. Therefore, the state
of health of the forests visited in the
Federal Republic of Germany and in
the eastern United States is illustrat-
ed by more than eighty photographs
The rapid spread of forest damage
in the Federal Republic of Germany
(FRG) is documented by the follow-
ing figures. While surveys showed
(that "only" 8 % of all trees were af-
fected in 1982, this figure rose to
34 % in 1983, and was estimated to
be 50 % in 1984, and 52 % in 1987.
When this alarming problem be-
came apparent in 1982, the German
Federal Ministry for Research and
Technology promoted and financial-
ly supported interdisciplinary stud-
ies on cause and effect relation-
ships in forest decline, with regional
emphasis on specific sites. This re-
search has the goal of increasing
our understanding of the complex
overall picture and our recognition
of links between causes and effects
In the eastern United States, da^
mage to conifers has also become
evident during the last several
years. Analyses of annual growth
rings of red spruce, slash pine and
loblolly pine show that growth rate
reductions have occurred since
the 1960s. Increased thinning of the
canopies of red spruce can also be
observed independent of tree age.
Regions of damaged red spruce
stands extend from southeastern
Canada to the southern Appalachi-
ans, But, the extent of forest decline
in the eastern United Stales is much
less than in the Federal Republic of
Germany.
From preliminary results of cause-
effect research, it became clear to
scientists that atmospheric pollution
probably plays a decisive role in the
development of the decline syn-
drome. Since the atmosphere over
all industrial nations contains harm-
ful pollutants which can be trans-
ported across national boundaries,
it is apparent that if air pollutants are
involved, forest decline is an envi-
ronmental problem that can only be
solved through international coop-
eration. Such cooperation between
scientists from the Federal Republic
of Germany and the United States
was initiated with the exchange of
information described here.
6
-------
Participants in the U.S. excursion of the American-German exchange, at Bi/tmore Castle in Ashevitie, North Carolina.
Excursion Participants
Federal Republic of Germany
United States ot America
Prof. Dr. A. Huttermann
Dr. H. Kenneweg
Dr. B. Krahl-Urban
Prof. Dr. K. Kreutzer
Dr. E. Matzner*
H.E. Papke
K. Peters
Dr. B. Prinz
Dr. B. Rami*
Prof. Dr. K.E. Rehfuess
Prof. Dr. P. Schutt
Prof. Dr. B. Ulrich
Prof Dr W Zech
Prof. Dr. H. Zottl
* German excursion only
University of Gottingen
University of Gottingen
Julich Nuclear Research Center
University of Munich
University of Gottingen
Julich Nuclear Research Center
Julich Nuclear Research Center
State Institute for
Air Pollution Research, Essen
Federal Ministry for
Research and Technology
University of Munich
University of Munich
University of Gottingen
University of Bayreuth
University of Freiburg
Dr. R. Bruck
Prof. E. Cowling
Prof. A.H. Johnson
Dr. D. Johnson**
Prof. R. Klein
Dr. S. Lindberg
Dr. S. McLaughlin
Dr. W. Robertson
Dr. R. Rosenthal
North Carolina State University-
North Carolina State University
University of Pennsylvania
Oak Ridge National Laboratory
University of Vermont
Oak Ridge National Laboratory
Oak Ridge National Laboratory
A,W. Mellon Foundation
U.S. Environmental Protection Agency
Canada
Dr. G. Robataille Canadian Forestry Service
Belgium
E. Laitat Faculty of Agronomy, Gembloux
'* American excursion only
7
-------
Excursion
through the
Federal Republic
of Germany
The route to the
research sites
in Germany:
State institute for
Air Pollution Research
in Essen, Eggegebirge,
Hits, Soiling and Harz,
Fichteigebirge,
Bavarian Forest,
Munich Gravel Plain,
and the Black Forest.
Hamburg
Amsterdanj
NETHERLANDS
Berlin
Hanover
GERMAN
DEMOCRATIC
REPUBUIK
Cologne
Brussels
¦
BELGIUM
-fa\yc*>f O
Frank
• LUX:.
7)
CZECHO-
SLOVAKIA
0
Nuremberg
FRANCE
Munich ¦
SWITZERLAND
AUSTRIA
*
The bus - means of transport and
forum for discussion.
In mid-May, 1984, an international
group of research scientists under-
took a one-week scientific excur-
sion, travelling together by bus, to
forest decline areas of the Federal
Republic. The route started at the
State Institute for Air Pollution Pro-
tection in Essen and continued
through the Eggegebirge, Nils, Sol-
ling and Harz, Fichteigebirge, and
Bavarian Forest near Bodenmais, to
the Black Forest near Freudenstadt.
With one exception, the visited sites
are research areas supported by
the German Federal Ministry for Re-
search and Technology. At each
site, the participants received first-
hand information, since at least one
of the participants was involved in
research at the site.
State Institute for
Air Pollution Research
At the State Institute for Air Pollution
Research (LIS) in Essen, North
Rhine-Westphalia, the participants
were shown the work in progress
on the effects of atmospheric pollut-
8
-------
Professor Fritz Fiihr, Project Management for Biology, Ecology and Energy of the Julich Nuclear Research Center, talking
to Professor Arthur Johnson, University of Pennsylvania, leader of the American delegation (from left).
ants on forests. Particular attention
is being given to phytotoxic effects
of ozone (03) and other photochem-
ical oxidants to test the hypothesis
of Dr. Bernhard Prinz and his col-
leagues that high concentrations of
ozone are a major cause of needle
loss of conifers. Studies in green-
houses of the State Institute for Air
Pollution Research relate tree
growth to various pollutant concen-
trations.
Eggegebirge
The next stop was in the Eggege-
birge, 150 km to the east of Essen.
Here, atmospheric pollutants from
the Ruhrgebiet, the largest industrial
area in Germany, for the first time
strike mountains as they are carried
by westerly winds. The State Insti-
tute for Air Pollution Research is in-
vestigating the amount and impact
of these pollutants, using open-top
exposure chambers. The Norway
spruces in the Eggegebirge show
chlorosis and loss of needles. Prinz
and his colleagues attribute this to
direct effects of ozone and to poor
site conditions. (-* Complex high
elevation hypothesis.)
Hits
The second day of the excursion
led to the Hils, Soiling, and Harz.
The Hils is part of the Weserberg-
land and lies about 50 km east of
the Eggegebirge. It is wooded with
Norway spruce and is an area re-
ceiving high input of acids from the
atmosphere, which is suspected to
become apparent in increased soil
acidification. Professor Bernhard Ul-
rich was able to demonstrate this
soil acidification to the participants
using young spruce. As a result of
the acidification, the roots do not
penetrate the mineral horizons as
usual, but remain in the shallow hu-
mus layer.
Soiling
The Soiling region is south of the
Hils, about 25 km northwest of
Gottingen, and reaches an elevation
of up to 500 m. The various measur-
ing systems on the research sites
were very noticable. Some of which
were installed above and below the
canopy on a tower and others at
ground level. Intensive ecological
investigations have been carried out
on these sites since the 1960s as
part of the International Biological
Research Program (IBP). In the
course of this research, Professor
Ulrich has observed increasing
soil acidification. He explains this
change as being due to deposition
of acidifying substances from the at-
mosphere. This long-term acidifica-
tion process leads to release of alu-
minum ions from the mineral soil
and bedrock. Aluminum ions avail-
able to plants may have a toxic ef-
fect on fine roots, depending on the
nutrient status of the soil.
(-* Acidification hypothesis.)
Harz
The next stops were at research
sites in the Harz Mountains, north-
east of the city of Gottingen. Over
1000 m in elevation, the Harz is the
highest mountain range in northern
9
-------
At the research site "Hohenkirchner Forst" near Munich Professor Peter Schutt, University of Munich, comments on h
genera/ stress hypothesis. On the left, Prof. Ellis Cowling, North Carolina State University.
Germany, and has its eastern por-
tion in the German Democratic Re-
public.
Because of its elevation, the Harz
region receives more precipitation
than Soiling and Hils. Here, the par-
ticipants first saw Norway spruce
with striking chlorosis and extreme
loss of needles. Near the town of
Braunlage the route passed through
an area where the forest has com-
pletely vanished in recent years.
The forest was the result of an early
reforestation effort and consisted of
a variety of low-land spruce that
was inappropriate for the area.
Fichtelgebirge
On the third day of the excursion
there was a long trip from the Harz
to the Fichtelgebirge. The time was
effectively used by the participants
in discussions of the sites visited so
far and preparatory lectures on sites
still to be seen. The Fichtelgebirge
is in northeastern Bavaria, in a tri-
angle formed by the Federal Repu-
blic of Germany, the German Demo-
cratic Republic, and Czechoslova-
kia.
The most severe damage to forests
in the Federal Republic can be
found in the Fichtelgebirge. This
was particularly striking because, at
the time of the excursion, the light
green of spring shoots is normally
dominant. For the German partici-
pants, the unusual sight of dead
trees on the Schneeberg was parti-
cularly shocking. The American par-
ticipants were more familiar with this
kind of sight in their natural, less in-
tensively managed forests.
Bavarian Forest
The next day, some research sites
were visited on the Grosser Arber
(1456 m), the highest point in the
Bavarian Forest. The excursion par-
ticipants were met by German For-
est Service officials who reported
on the alarming developments in
their region. Spruce on the research
sites showed extreme chlorosis and
the "silver tinsel" syndrome. Very
severe symptoms were observed
on the "Luchsplatzl" at an elevation
of 1200 m All declining forests in
the FRG were additionally affected
by severe infestation by bark beetle
in the preceding season. This was
particularly apparent at the "Luchs-
platzl" site, where dead trees had
been left standing.
Munich Gravel Plain
The research site "Hohenkirchner
Forst" near Munich was visited on
the fifth day of the excursion. The
old-growth spruce stand showed
thin crown due to loss of older nee-
dle sets. In contrast to the other
sites visited, there was no evidence
of chlorosis at the Hohenkirchner
Forst site. Natural regeneration of
young spruce appeared normal.
Bavarian Alps
A visit to the "Elendalm" site in the
Schlierseer Mountains had been
10
-------
Professor Bernhard Ulrich, University of Gottingen, demonstrates the results obtained at a research site in the Hits Moun-
tains. Attentive listener, Helmut Papke, Jiilich Nuclear Research Center.
Dr. Bernhard Prinz, LIS Essen, examin-
ing spruce needles.
planned for the same day, but had
to be canceled for lack of time. This
site was visited and documented on
a later occasion. Some sections of
the Norway spruce stand on the
"Elendalm" are dying. Still vital trees
show meager growth and severe
chlorosis. However, in the Alps, this
has always been a problem on
south-facing slopes with shallow,
rocky soils.
Black Forest
The sixth and last day of the excur-
sion was limited by lack of time to
sites in the northern part of the
Black Forest. The Black Forest
shows the most severe decline of
silver fir: in 1984 only one tree in
twelve was healthy, Since two-thirds
of the Norway spruce, the main spe-
cies in the Black Forest, are also
damaged, the participants found
this forest in a miserable state. Just
how threatening this situations is,
deeply concerns the local foresters
and was mentioned in all discus-
sions.
Until reaching the Black Forest this
German-American scientific ex-
change had not been discovered by
the media. Here, however, an Amer-
ican TV team was awaiting our arriv-
al. But interviews and statements
from individual participants could
have upset the basis of mutual trust
that had developed in the group
and could have revived earlier differ-
ences. After separate discussions
with the American and German
participants, a compromise was
reached with the TV team and no in-
terviews were given. The TV team
was to work solely with the local for-
esters. Thus the excursion in the
Black Forest could be carried out
without disruption. The situation
was different in the United States
when Mount Mitchell was visited,
The German excursion ended in the
Black Forest with a preliminary con-
cluding discussion that was contin-
ued on the visit to the United States.
11
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Hudson Bay
~N CT
Excursion through
the Eastern
United States
CANADA
Montreal B
Whiteface Camels Hump
Chicago
lak Ridge^".^ # IVlt.Mitchell
Smoky MlnsV-^^Ashville /
)/^Atianta /
The route of the
American excursion
to affected forest sites
in the Appalachian
Mountains:
New York,
Burlington,
Green Mountains
and Adirondacks in the Northern
Appalachians;
Mount Mitchell and the Smoky
Mountains in the
Southern Appalachians.
Rangers from the National and State
Parks visited were interested In dis-
cussions with the participants of the
scientific excursion.
At the end of June 1984, nearly the
same group of participants made a
one-week excursion to aflected for-
ests in the eastern United States.
The American trip went from Bur-
lington, Vermont, through the Green
Mountains, the Adirondacks (New
York) to Mount Mitchell and the
Smoky Mountains in the Southern
Appalachians. As in Germany, re-
search was being carried out at
every site visited by at least one of
the participants. Compared with the
research in the Federal Republic,
the work here is still in the initial
stages. Nevertheless, there are
many preliminary data which show
that forest decline is also an envir-
onmental problem in the United
States.
Green Mountains
The first sites visited in the Northern
Appalachians were on Camels
Hump (1280 m). Camels Hump re-
12
-------
On Mount Mitchell, North Carolina, Dr. Wayne Robarge, North Carolina State University, reported the results of soil ana-
lyses. The German soil scientists Wolfgang Zech, Karl Kreutzer and Heinz Zotti are interested listeners.
presents a typical mountain on the
main ridge of the Green Mountains
in Vermont. The ascent of Camels
Hump began in a zone of deciduous
forests, followed by a transition
zone from deciduous trees to coni-
fers, and a high-montane conifer
zone above that. European partici-
pants were impressed by the large
number of tree species, the height
of the trees, and the natural state of
the stands in the deciduous zone.
Apart from the dominant species -
sugar maple, beech, and yellow
birch - there are many other decid-
uous species scattered as individu-
als throughout the forest.
Above about 900 m, damage to red
spruce first became evident. Parti-
cularly shocking was the fact that
practically all the older trees were
dead, projecting starkly from the
green of the younger trees, a sight
that is unknown in the Federal
Republic of Germany because da-
maged or dead trees are cut regu-
larly as a management measure.
However, the situation appears
hopeless only at first glance, for
normal regeneration can be seen
between the dead trees. Balsam fir,
which has been less affected, re-
generates better and seems to be
displacing the previously dominant
red spruce. The American experts
attributed the severe damage in this
area to a weakening of the trees by
extreme drought in the mid-1960s
and to effects of air pollutants.
Adirondacks
The next destination was Whiteface
Mountain in the Adirondacks of
New York. Red spruce on Whiteface
shows damage similar to that on
Camels Hump. In the spruce-fir-
birch forest, 85 % of the dominant
red spruce has been damaged or
has died over the last 20 years. Par-
ticularly striking is the way balsam
fir appear to die in waves in the
high-elevation conifer forest. This is
not a novel decline, but a natural
phenomenon. Balsam fir is a short
lived species which, after reaching
its natural age limit, simply dies off
in small groups.
On the summit of Whiteface Moun-
tain there is a meteorological station
where continuous measurements
of pollutants in clouds and fog are
made. There is no research station
with equivalent equipment and staff
at the German forest research sites.
Mount Mitchell
The participants flew from Albany,
New York, to Asheville, North Caro-
lina, in the Southern Appalachians.
There, the next excursion was to
Mount Mitchell (2039 m) in the Black
Mountains. The summit was easy to
reach by car on the road to Mount
Mitchell State Park.
13
-------
Professor Arthur Johnson, University of Pennsylvania explaining specific observations. Listening are Dr. Dale Johnson
and Dr. Steven Lindberg, Oak Ridge National Laboratory, and Professor Wolfgang Zech, University of Bayreuth.
In the Southern Appalachians, there
is zonation by elevation similar to
that in the Northern Appalachians of
deciduous forests, transition zone,
and coniferous forests on the upper
slopes. Due to the southern lati-
tude, the zone boundaries are shift-
ed a few hundred meters higher. On
Mount Mitchell there is severe de-
cline of red spruce and Fraser fir.
Since nearly all the fir stands are in-
fested with the wooly adelgid, mea-
suring the damage and finding the
causes are made more difficult. The
stands are clearly dying.
Mount Mitchell was also attractive to
the media, representing to them an
"acid rain damaged forest", even
though the most apparent damage
is due to insects. Therefore, it was
not surprising that practically all the
participants were interviewed on
Mount Mitchell by local TV stations
and newspapers. In the evening
and next day, the media reported
extensively on the German-Ameri-
can scientific exchange.
Dr. Robert Bruck, North Carolina State University, comments on his studies.
14
-------
Intensive discussions in the deteriorating forest on Mount Mitchell between Dr. Russell Rebertus, North Carolina State
University, Professor Wolfgang Zech, University of Bayreuth, and Dr. Jerry S. Olson, ORNL (from left).
Smoky Mountains
The Great Smoky Mountains Na-
tional Park was the last area visited.
This National Park was founded in
1926 and covers a densely wooded
area of 2020 km2. The landscape of
the Smoky Mountains is compar-
able to that of the German Black
Forest. The most striking difference
is that from every point in the Smo-
kies one sees a closed canopy with
no clearcuts or meadows. Even to-
day, black bears are found in the
area.
tin the Smoky Mountains the Ger-
man participants discovered initial
stages of decline in the high-eleva-
tion spruce forests. This has since
been confirmed by American ex-
perts.
Oak Ridge
National Laboratory
The planned visit to Oak ridge Na-
tional Laboratory had to yield to a
concluding discussion session, but
immediately after the official pro-
gram a smaller group visited Oak
Ridge to document research efforts
there.
At Oak Ridge National Laboratory,
field and laboratory investigations
study the influence of atmospheric
pollutants on forest trees. Natural
environmental conditions can be
simulated in climate chambers. In
these experiments, several para-
meters, e. g., the pH value of artifi-
cial rain, can be varied. At Walker
Branch Watershed, field measure-
ments of deposition rates are carri-
ed out with complicated monitoring
instruments above and below ca-
nopy.
Concluding Discussion
In Asheville, a full day of discus-
sions formed the scientific conclu-
sion of the two excursions. In small
working groups, and all together in
the large group, an effort was made
to distill general findings, similari-
ties, and major hypotheses from the
large amount of details exchanged
by all participants. The German and
American scientists provided a
common base of field observations
to facilitate the comparison of de-
cline symptoms, site characteris-
tics, and atmospheric deposition.
The merits of various hypotheses to
explain forest decline were debated
and new thoughts were put forward.
Promising approaches for future re-
search and possibilities to test the
different hypotheses were summa-
rized.
15
-------
The Forest
An Ecosystem
H.E. Papke and B. Krahl-Urban
Julich Nuclear Research Center
Forests are the naturally dominant
form of vegetation in Central Europe
and in eastern and western North
America. In early geologic history,
before the Ice Ages, both conti-
nents were covered by forests with
many varieties of trees and a similar
mixture of species. In the course of
four prolonged cold periods and
succeeding warm intervals the for-
ests underwent major changes re-
sulting in differences in vegetation
between Central Europe and North
America today.
Each Ice Age caused a temperature
drop in the northern hemisphere
such that tree species could survive
only in the warmer southern areas.
In Central Europe, the geographical
obstacle of the Alps or, more prob-
ably, the particularly unfavorable
zone of retreat between the south-
ern alpine glacier edge and the bar-
rier of the Mediterranean led to the
extinction of many plant and tree
species. Many varieties of plants
could not survive the influence of
Ice Age cold from the North and
the African desert climate from the
South. As a result of repeated shifts
in their areas of distribution and
associated selective pressures, the
previously very rich flora of Central
Europe became impoverished,
losing several genera entirely.
The North American forests were
also subject to the climatic hot and
cold spells during the Ice Ages and
intervening periods. Because the
mountains run predominantly from
north to south (e.g. Rocky Moun-
tains, Appalachians) the flora could
retreat southward with practically no
obstacle. Between the southern
edge of the arctic ice shield in the
North, the climatically favorable sea
coasts of the Gulf of Mexico in the
South, and the Atlantic Ocean in the
East, the various types of vegetation
survived in compressed zones.
After the ice masses melted, the
plants once more expanded their
distribution. Thus, the forests cur-
rently found in North America to a
large extent have the same compo-
sition as the pre-lce Age forests.
Today, then, in North America there
are 18 coniferous and 57 deciduous
tree species, while there are only
8 coniferous and 32 deciduous spe-
cies in Central Europe.
After the ice masses had moved
back north, the treeless cold
steppes (tundra) were initially inha-
bited in the ensuing warm periods
by trees of so-called pioneer spe-
cies, which made relatively modest
demands with regard to climate and
soil. Among these light-loving and
quite frost-resistant species are the
willow, pine, birch, and hazel. In a
later phase there followed oak, elm,
maple, and spruce, and finally fir
and beech.
The Forest Ecosystem
The forest is an association of
plants, animals, and microorga-
nisms in a particular area. This area
is determined by the abiotic envi-
ronmental factors soil and climate,
and especially by the supply of
water and nutrients, light and heat.
The forest is an especially complex
ecosystem. In and on the forest
floor, at various levels within the
stand, from the roots to the canopy,
organisms are connected to each
other and their environment by in-
terrelationships of different degrees
of sophistication. They play a deci-
sive part in determining the charac-
teristics of their environment. The
forest ecosystem houses a large
variety of producers (trees, shrubs,
bushes, herbs, and grasses), con-
sumers (birds, wild animals, bee-
tles, and butterflies) and decompo-
sers (worms, insects, fungi, and
bacteria).
An ecosystem can function when at
least two biological components,
the producers and the decompo-
sers, are present: the former create
material, the latter break it down. A
food chain of consumers can be in-
serted into this cycle. It is important
for the ecosystem that the nutrient
cycle is preserved.
The forest ecosystem has a particu-
larly large variety of different produ-
cers, namely, all green plants. They
range from full-grown trees to
16
-------
Since the end
of the last Ice Age,
forests have dominated
the landscapes of Central Europe
and the eastern United States of America.
herbs, grasses, ferns, and moss
growing on the forest floor. These
are called primary producers be-
cause photosynthesis occurs in
their leaves. This process is based
on the capability of the green parts
of the plants to build, with the help
of solar energy and chlorophyll,
their own organic compounds,
using nutrients and water. The leaf
takes in carbon dioxide (C02)
through microscopic openings (sto-
mata), and in various complicated
reactions with hydrogen this is con-
verted to glucose. During this pro-
cess large amounts of oxygen are
released to the atmosphere. The
plant needs glucose for its own re-
spiratory metabolism.
Glucose is also the basic sub-
stance for the synthesis of most
organic substances (assimilates).
To create these, the plant needs
additional mineral nutrients such as
nitrogen, phosphorus, potassium,
magnesium, and calcium, which are
taken up by the roots or leaves.
From these assimilates, roots,
leaves, fruits, wood, and bark are
created by further biochemical pro-
cesses.
Consumers are either herbivores
living directly on the organic sub-
stances built up by plants, or car-
nivores living indirectly from the
plants by eating herbivores and
other carnivores.
Organic substances from dead or-
ganisms are used by the decom-
posers, which are divided into detri-
tus feeders and reducers. Detritus
feeders (e.g. worms and woodlice)
fulfill the important task of breaking
down vegetable material and animal
remains (leaves, needles, branches,
animal carcasses, etc.). The redu-
cers (soil microorganisms, such as
bacteria and fungi) convert the or-
ganic remains to the original inor-
ganic substances, i.e. they mineral-
ize them to nutrients which the
plants can take up. Reducers are
therefore also called mineralizers. In
this manner they ensure that the nu-
trient cycle is closed. Through this
natural recycling, decomposers en-
able the forest ecosystem to exist
practically forever on the same site.
17
-------
/ / /
/ / / / / / /
/ / / / / / /
/ / / / / /
/.//// /
// //
Herbivores
Solar Energy
Producer
Photosynthesis
h
Carnivores
Evaporation
Detrivores
Minerahzers
The Forest Ecosystem
The major components, relationships and processes in the forest ecological system are presented here in simplified form.
The forest is a community of producers, consumers and decomposers in a specific area, the biotope. The green plants
are the producers. With the help of photosynthesis they create high-molecular organic compounds from simple inorganic
substances. The plant tissue forms basic food for herbivores, which in turn are the prey of a number of insectivores and
carnivores. Dead organic substances are converted to humus by detrivores. Mineralizers see to the reduction of the
molecular organic substances to simple inorganic compounds.
As regards their energy balance, ecological systems are open systems which take up energy from the sun. The natural
cycles of substances in the forest ecosystem, on the other hand, are balanced, so that a forest can continue existing on
the same site practically for ever.
The living and non-living compo-
nents of the ecosystem are closely
interlinked by the flow of energy and
the food cycle. Thus the ecosystem
has a functional unity with self-regu-
lating mechanisms to counteract a
certain amount of disturbance.
The relationships in the ecological
system are of course much more
complex than one can portray in a
simple diagram. As an example,
one may consider the different roles
of earthworms in the ecosystem. In
the forest, earthworms are decom-
posers and active in the formation
of humus. On the other hand they
are the basic food for many crea-
tures, and function then as so-
called secondary producers. De-
pending on its position in the food
chain, an organism may be con-
sumer, decomposer or secondary
producer,
Many animals not only profit from
plants, but also help them, for in-
stance in pollination and dissemina-
tion of seeds (insects, birds, mam-
mals). Other animals serve the
plants as regulators by keeping the
population of herbivores under con-
trol (the food pyramid). The various
food chains and food pyramids are
themselves interlinked to form com-
plicated food webs.
Because of the links outlined above,
an ecological system taken as a
whole reacts differently from its indi-
vidual parts. Thus a tree in a nursery
will react differently from one in a
forest. The characteristics of an
ecosystem are not the same as the
sum of the characteristics of its
18
-------
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economic usefulness, protection and recreation.
A managed forest of spruce,
fir and beech-in the Central Black Forest.
Such a forest
can optimally fulfill its functions of
19
-------
Solar Radiation
, / Precipitation
Oxygen
Carbon Dioxide
Evaporation
t
.o:vfc-'-'v.- •• ao- — ... . ~ _
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, Nutrients
Assimilates
"and Water. t.
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Photosynthesis and Metabolism
The canopy of a deciduous forest contains about 63 million leaves per hectare.
Photosynthesis, the most important biological process for life on Earth, takes
place in the leaves. With the help of this process almost the entire amount of
organic matter on Earth is produced, thus providing an energy supply for practi-
cally all living beings. The relatively complicated process of photosynthesis can
be explained in simplified form as follows: leaves produce glucose from carbon
dioxide (COJ taken in through microscopic openings, and from water (H20)
taken up by the roots, with the aid of solar energy and chlorophyll. The oxygen
produced by this reaction is given off to the atmosphere. A t the end of a grow-
ing period, ten leaves have formed the equivalent of a sugar lump (4 g).
Almost two-thirds of the carbohydrate produced is used for the tree s active
metabolism (breathing); only a third is available for growth, and much of this is
used for the periodic renewal of lea ves and roots.
The canopy of a forest should not be regarded simply from the production
aspect; at least as important are the effects on the ecological system via the
conversion of heat and light, and the turnover of water and nutrients. Deciduous
trees have a greater effect on the forest ecosystem than do conifers because of
their annual loss of lea ves. This process stimulates the food cycle and alio ws
light and heat to reach the ground, which accelerates mineralization of the Utter.
The existence of early blooming plants (anenomes, primroses, ect.) is linked to
the extra light before the leaves come out.
i -X '
The right hand picture shows the crown of a 750-years-old oak in the Spessart.
It has a height of 30 m, a circumference of 5 m and a wood volume of 30 m3.
20
-------
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fowowmtr
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-------
The forest not only assures supplies of wood. The highly active filtering effect ot
the forest soil on water makes it indispensable in densely populated industrial
countries. Additionally, it regulates the water flow.
parts. The favorable effect of a forest
on its surroundings exists only if the
stand is closed (densely growing).
The same effect is not found when
the same number of trees are grown
at a distance from one another. Cer-
tain organisms can only survive in
the long term in a forest ecosystem.
Without doubt, Man has the grea-
test influence on the forest ecosys-
tem. It is in his hands to preserve it,
to change its living conditions, or to
destroy it, Thus Man goes far be-
yond his position in the food chain.
Natural ecological systems such
as the forest are not dependent on
Man and other consumers. Man,
however, does need the forest for
himself and his environment.
Natural
Forest Communities
The original forms of forest in Cen-
tral Europe were naturally regener-
ating mixed deciduous woodlands.
Until the era of extensive clear-
cutting between 800 and 1000 AD.,
they covered about th'ree quarters of
the land area. Today about 30% of
Europe is still wooded. The major
natural forest communities found in
Europe and eastern North America
are described in the following sec-
tions They are named afterthe domi-
nant tree species.
Mixed Beech Forests
Beech is the most important of the
deciduous trees of Central Europe.
Beeches are growing up to the
montane zones. In southwestern
Germany, it is generally found
associated with spruce, fir, and var-
ious other deciduous trees, forming
the mixed montane forest. The com-
position of this forest type varies ac-
cording to silvicultural practices.
Mixed Oak Forests
Natural mixed oak forests are grow-
ing in the climatically more favor-
able warmer areas. In the Federal
Republic of Germany they are most
common in the Pfalzerwald, Steiger-
wald, and Spessart. In these mixed
forests, oak is associated with horn-
beam, red beech, or birch, depend-
ing on soil conditions.
Mixed Montane Forests
At higher elevations in the moun-
tains one may often find mixed for-
ests, mostly composed of equal
proportions of spruce, fir and
beech, with a sprinkling of other
species, such as sycamore, moun-
tain elm, pine, and larch. Such for-
ests are mainly in the southern
Black Forest, the Bavarian Forest
and the Alps.
Spruce Forests
Natural (autochthonic) spruce for-
ests can still be found in a few of
the higher parts of the Harz, the
Fichtelgebirge, the Bavarian Forest,
and the Calcareous Alps. Best con-
ditions for spruce are in the rainy al-
pine and sub-alpine regions. There
it grows at elevations up to 1700 m.
Riparian Forests
In areas subject to flooding along
rivers, natural stands of softwood
(poplar and willow) or hardwood
(oak, ash, elm, and beech), depend-
ing on flood frequency, formed ri-
parian forests. Following agricultural
utilization and regulation of the
rivers, only remnants of these re-
main.
Natural forests in North America dif-
fer from those in Central Europe by
their greater number and different
combinations of species. In the
eastern United States, forests are
composed mainly of deciduous
trees; conifers are growing only in
the highest regions of the Appala-
chians.
In the mixed forests of the Appala-
chians, depending on the quality of
the soil, a variety of trees dominate
in individual locations. On the rich-
est sites horse chestnut, sugar
maple, yellow birch, silver linden,
22
-------
Fungi as decomposers in the natural cycle of the forest ecosystem assure the
decomposition and mineralization of organic substances. Thus seeds are able
to germinate and plants obtain the necessary food.
oak, and yellow poplar are most im-
portant. On soil of moderate quality,
one finds largest proportions of
sugar maple, red oak, yellow birch,
American beech, and yellow poplar.
Red oak, scarlet oak, and pine are
found on the poorest and driest
sites. American beech is less com-
petitive, in all communities, than the
other most important species
named. Thus, it never dominates
entire forests as the European
beech does.
The high-montane area of the Ap-
palachians is covered with dense
coniferous forests of spruce and fir.
In these forests, the proportion of fir
increases considerably with eleva-
tion. One regularly finds islands of
yellow birch, striped maple, moun-
tain ash, and fire cherry. Of the
many natural forest communities of
North America, two representative
but differing ones from the southern
Appalachians are presented here.
Mixed Forests of Horse
Chestnut and Sugar Maple
On the richest sites in the montane
zone one finds the horse chestnut -
sugar maple - forests. The domi-
nant species here, which grow to a
height of up to 30 m, are sugar ma-
ple, yellow horse chestnut, silver
linden, and ash. Within this combi-
nation, sugar maple is usually domi-
nant. Despite the wide variety of
trees, stands which have not been
disturbed mostly form a unified,
thick, shady vaulted forest, similar
to the beech forests of Europe.
Mixed Forests
of Yellow Poplar
In the sub-montane zone of the
southern Appalachians, one finds a
dense, tall mixed deciduous forest
with a multi-layered canopy. The
most striking and most widely dis-
tributed tree is the yellow poplar,
which can reach a height of up to
60 m. Depending on local site con-
ditions, it grows together with sugar
maple, horse chestnut, and beech,
or with various species of oak, dog-
wood, oxydendron, red maple and
sassafras.
As a result of increasing wage costs
in recent decades, and timber
prices stagnating at the same time,
there are years in which the income
of many state forests in the Federal
Republic of Germany does not meet
the expenses. However, since the
Federal Republic must import more
than half the timber products it re-
quires, controlled forestry is indis-
pensable. Only stands growing on
sites of difficult access or under ex-
treme conditions are left to them-
selves. In addition, on specific sites,
small plots are excluded from forest
management and used to study nat-
ural forest dynamics.
The past has shown that naturally
regenerated, multi-layered, mixed
stands are less subject to insect at-
tack than cultivated single-species
plantations. Mistakes in dealing
with the forest ecosystem cannot,
however, be corrected in the short
term Because of the slow growth of
trees, changes in species composi-
tion may take fifty to one hundred
years to become established.
Human Intervention
About 2000 years ago Central Eu-
rope was covered by a mixed de-
ciduous virgin forest with beech
predominating. Only about 10 to
20% of the forest was cleared for
raising crops and livestock. In the
Middle Ages there followed much
clearing because of the great need
for agricultural land, settlements,
and roads. Two thirds of the original
forest disappeared. From the early
Middle Ages to the 19th century,
the forest served the population as
a supplier of timber for building and
burning, energy in the form of char-
coal, food in the form of fruit, and
grazing for livestock.
In the 18th and 19th centuries, for-
est clear-cutting reached such pro-
portions because of the need for
building material, paper manufac-
23
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above vineyards to prevent cold air
seepage down the slope.
Wind Protection
The forest reduces wind speed con-
siderably; the effect is still measur-
able at twenty times the height of
the canopy. Fields in the wind sha-
dow of forests produce up to 30%
more crops. This is because wind
increases transpiration of plants.
Plants try to prevent this by closing
the stomata of leaves and needles.
This in turn affects the uptake of car-
bon dioxide from the atmosphere,
important for photosynthesis, and
can result in lower yields of cultiva-
ted crops.
Recreation Area
Forests provide Man with opportu-
nities for recreation. According to
recent statistics, in the Federal Re-
public of Germany they represent
the most important recreational
areas of all. A survey has shown
that only 7% of the German popula-
tion never visits the forest. City
dwellers throng there because of
the clean air and the longed-for
contrast to the noisy urban atmos-
phere with its polluted air.
There is a similar trend in the United
States. The Great Smoky Mountains
National Park in the southern Appa-
lachians, for example, is a popular
goal for trips. Because of its close-
ness to the industrial centers of the
East, it is gaining in importance as a
recreational area. In the summer
United States of America
months, many visitors come from
the humid lowland areas to experi-
ence intact virgin forest in the cool
mountain woods of the park.
Habitat for
Animals and Plants
The richness of forest flora and fau-
na is primarily due to the fact that
forest communities are not dis-
turbed by regular cultivation of the
soil or frequent use of fertilizer. The
biological cycle of development of
plants and animals is only interrupt-
ed after major intervals of time (tim-
ber harvest). The forest ecosystem
has so many options for self-regula-
tion, as mentioned above, that plant
care products and weed killers are
only needed for a small portion of
the wooded area. With near-natural
forestry practices on favorable sites
it is usually possible to do without
pesticides.
Source of Raw Materials
The forest has an important eco-
nomic function as a supplier of raw
materials. In earlier times, the forest
was used as a source of wood and
forage. Today it provides the raw
materials primarily for the timber
and paper industries. In the Federal
Republic of Germany, three-quar-
ters of the demand is met by conif-
ers.
Ecological Backbone
of the Land
The manifold contributions of the
forest ecosystem to the protection
of the environment justify calling it
the ecological backbone of the
land. It is important to realize that
not only virgin forests, but also
managed forests can play a part in
environmental protection.
Stability and
Stress Resistance
of the Forest Ecosystem
One of the most important charac-
teristics of ecosystems is their tend-
ency toward a stable state (climax)
of ecological development under
given climatic and soil conditions.
In Central Europe and North Ameri-
ca, as in practically all areas of the
world, forests are close to such an
endpoint. They proceed through a
succession of unstable forms of
vegetation, following the same
principle behind resettlement of the
cold steppes after the Ice Ages.
Wherever fallow land or bare patch-
es are resettled after clear-cutting
or fire, the ecosystem proceeds
through various unstable pioneer
stages in succession until climax is
reached and equilibrium establish-
ed. The driving force is competition
between species for light, water,
and nutrients. Under natural condi-
tions, this development can take
several hundred to a thousand
years, depending on the type of for-
est. From a pioneer system which is
affected by external factors, a stable
climax ecosystem largely shielded
from outside influences develops in
the course of succession. The final
stage is characterized by "internal
control" in the form of a web of stab-
ilizing interactions.
Ideally, biomass production and
break-down (mineralization) are in
balance in the climax stage. This is
termed the biological or ecological
equilibrium of the system, whereby
a dynamic state of balance is under-
stood. Just as the abiotic factors
(weather, temperature, etc.) are sub-
ject to variation, the ecological equi-
librium varies slightly around a
mean condition, Qualitatively, the
spectrum of species remains the
same. The greater the number of
species and the denser the web of
interrelationships, the greater is the
stress resistance of an ecosystem.
The self-regulating capacity of a for-
est ecosystem is limited, however.
if)
C
o
c
o
c
o
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Long Range Transport
Spatial dispersion of emissions and deposition of pollutants. The emitted pollutants remain for differing periods of time in
the atmosphere, depending on the height of the source, wind conditions and other climatic and meteorological influences.
They can thus be transported a long way from their source. During this long range transport numerous pollutants react
with the oxygen in the air, with humidity, or with each other. The acids or photooxidants formed are often more toxic for
plants than the initial pollutant. Deposition can be in wet or dry form. When there is fog there is a particularly high input of
pollutants in the forests. The enormous surface area of leaves and needles acts as a filter for heavy metal dusts and liquid
and gaseous pollutants.
Long Range Transport
Fog
£Ik 1
Filter Effect-j|
Precipitation
Wet Deposition .
V ¦¦ v \
Dry Deposition
Leaching
DEPOSITION
TRANSMISSION
EMISSION
Short-term extremes (frost shocks,
drought, flood) can be countered by
the system during so-called recu-
perative phases (buffering capacity).
But, long-term stresses reduce sta-
bility of the system and lead finally
to destabilization. An example of
this was the former removal of litter
(loss of biomass) for forage in Ger-
man forests. More recently, stress
from atmospheric pollutants is such
a factor. The effects of long-term
natural or anthropogenic stresses
are often only recognizable after a
period of time, because of the elas-
ticity of the ecosystem.
Impact of Atmospheric
Pollutants on Forests -
A German View
The damaging effects of airborne
pollutants on vegetation have been
known since the beginning of the
industrial revolution in the early
1800's. Until the end of the 19th cen-
tury pollutant damage in Europe
was limited almost exclusively to
remote wooded mountain valleys
where ores were smelted.
With the establishment of big indus-
trial regions in Central Europe and
in the United States, previously
local damage spread over larger
areas. Bui forest damage was still
directly related to individual indus-
tries. The cause was large quanti-
ties of gaseous and particulate pol-
lutants from chimneys, then about
50 m high.
For about a decade now, decline
has been observed on forests far
from industrial areas. Damage was
first seen on the higher slopes of
wooded mountains exposed to
wind. Also, there seems to be a
i temporal correlation between the
construction and operation of tall
stacks (source heights of about
200 m) of major power plants and
damage 200 km or more distant.
The tall stacks built in the 1960's
brought about a considerable re-
duction of pollution in the immedi-
ate vicinity (up to 20 km), but the
higher the point of emission of pol-
lutants, the longer they remain in
the atmosphere. Depending on
wind, climate, and meteorological
conditions, air pollutants are trans-
ported various distances from the
point of emission (long range trans-
port). The Federal Republic of Ger-
many receives about half its sulfur
deposition from neighboring coun-
tries, and it exports about the same
amount.
From research results to date, it ap-
pears that atmospheric pollutants
could represent a major factor in the
complex development of forest de-
cline. Usually, though, single pollu-
tants are not likely the exclusive
cause, since in most places their
concentrations are below known
thresholds of acute damage to
1/ trees. But, it has been recognized
that the combined effects of a num-
ber of pollutants and their conver-
sion products (e.g. photooxidants)
and their interaction with natural
stress factors are important. Addi-
tive and synergistic interactions
have been confirmed experimentally
for combinations of the phytotoxic
gases sulfur dioxide and ozone,
I and sulfur dioxide and nitrogen ox-
ides. In addition to these gaseous
pollutants reacting with leaves,
there is also acidic precipitation,
which can have a leaching effect
mainly on the soil, but can also af-
26
-------
feet parts of the plant above ground.
The most important phytotoxic pol-
lutants are discussed below.
Sulfur Dioxide (S02)
The most prevalent atmospheric
pollutant which damages plants is
sulfur dioxide (S02). It is mainly
emitted when burning fossil fuels,
Total emissions of sulfur dioxide in
the Federal Republic of Germany in
1982 amounted to about 3 million
metric tons and in the US to about
21.3 million metric tons. Since 1970,
there has been a reduction in emis-
sions, small in the Federal Republic
and larger in the United States.
'Sulfur dioxide has a residence time
of one to three days in the atmo-
sphere. There it reacts with moisture,
forming sulfurous acid (H2S03), and
after oxidation with oxygen, con-
verts to sulfuric acid (H2S04). A ma-
jor portion of sulfur dioxide emis-
sions comes from power plants,
district and industrial heating plants,
and industrial furnaces and is emit-
ted via tall stacks into the atmo-
sphere. Through long range trans-
port, this pollutant reaches virtually
all Central European forests, where
average annual concentrations of 10
to 40 ng/m3 are measured. At times,
the damage threshold concentration
for S02 is reached or exceeded for
trees. In some regions, especially in
the Fichtelgebirge (p. 64), sulfur di-
oxide may be a decisive factor. This
is not the case in areas with less
sulfur dioxide, such as the Calcare-
ous Alps (p. 82).
Based on known dose-response
relationships, sulfur dioxide can be
excluded as the sole cause of re-
cent forest decline, but it is certainly
an important factor. There are still
basic gaps in our knowledge of the
physiological effects of high, short-
term concentration peaks.
Nitrogen Oxides (NOJ
Total emissions of nitrogen oxides
(NOx) both in the Federal Republic
of Germany and the US are about
90% of the respective sulfur dioxide
emissions. In contrast to sulfur di-
oxide emissions, the total output of
nitrogen oxides in the last 20 years
has increased 50% in the Federal
Republic and 20% in the United
States. Today there appears to be
no change in this trend.
At high combustion temperatures
over 1000°C, as found in large pow-
er plants and high compression
automobile engines, atmospheric
nitrogen reacts with oxygen to form
nitrous oxide (NO). In the atmo-
sphere, nitrous oxide (NO) then oxi-
dizes to nitrogen dioxide (N02). This
pollutant persists for 2 to 20 days,
and may be transported over great
distances.
Nitrogen oxides can react with wa-
ter to form strong acids. Nitric acid
is a major contributor to acidic de-
position to forests, but the nitrates
deposited also can act as fertilizer.
Nitrogen oxides can be excluded as il
the sole cause of forest decline.
They are less toxic than sulfur diox-
ide and, furthermore, are present in
lower concentrations. No assess-
ment can yet be made of the patho-
logical significance of gaseous nitric
acid.
Acid Rain
Sulfur dioxide and nitrogen oxides
can react with atmospheric oxygen
and water to form acids, The result
is acidic rainwater. Pure rainwater in
27
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Forest Decline in the Fed. Rep. of Germany in 1986
All Tree Species 0
(Damage categories 1-4)
Damaged area in % of total wooded
area in the region.
| >20-35
>35-50
>50-65
>65-85
BERLIN
(West) (East)
HAMBURG
BREMEN
HANOVER
Source:
Bundesminister fur Ernahrung.
Landwirtschaft und Forsten
X
Forest Decline Survey 1986
Status October 1986
r
Diagram: Umweltbundesamt/UMPLIS
•o Umweltbundesamt 1986
0 20 40 60 80 100 km
28
-------
,2.0-
cn
c
o
c
o
c
o
-------
Percentage
100 —
%
80-
60-
40-
20-
0-
Damage Category
Spruce Pine Fir Beech Oak Others Sum
Forest decline in the Federal Republic of Germany In 1985, in percentages of
damage categories within tree species. Altogether, 52% of the forest area is
damaged whereby 19% of the forests show a foliage loss over 25%.
Norway Spruce
The crowns of damaged spruce
trees are often thinned because
of the premature dropping
of the older generations of needles.
The quantity lost is a direct measure
of the degree of sickness.
Healthy spruces carry
up to eight generations of needles.
Forest Decline
Fed. Rep. of Germany
In the Federal Republic of Germany,
the Forest Decline Survey of 1986
was carried out according to the
same standardized sampling proce-
dures used in 1984 and 1985, so
that comparable results from three
survey years are available. This
method groups the sampled trees
by degree of damage, based on
loss of needles and leaves and yel-
lowing of foliage. Trees showing fol-
iage loss up to 10% are classified
as "healthy". Degrees of defoliation
for the damage classes "slight",
"moderate", and "severe/dead" are
11-25%, 26-60%, and greater than
60%, respectively. The survey was
carried out in the individual states
from mid-July to the beginning of
September. The main results of the
survey are presented below.
jlThe rapid increase in forest decline,
as observed since 1982, on the
whole has not continued. While, be-
30
-------
tween 1983 and 1984 the occur-
rence of damage rose from 34 to
50% of the forested area, from 1984
to 1986 there was only a slight in-
crease of 2% per year. Altogether,
forest trees on 4,0 million hectares
show reduced vitality or are declin-
ing. Nearly two thirds of the da-
maged areas have damage in cate-
gory 1 (slight damage). Assuming
this to be a warning stage, then
19% of the forest shows moderate
to severe damage (categories 2-4).
It was in this group that the increase
of forest decline occurred between
1984 and 1986.
Although the situation has improved
in individual areas and for individual
species, further damage is seen for
beech, and particularly oak. The si-
tuation of pine has improved slight-
ly. With 83% of the area covered by
fir showing damage in categories 1
to 4 and 61 % in categories 2 to 4, fir
appears acutely threatened. Beech
and oak now have a higher propor-
tion (60%) of damage by area than
spruce and pine (54%). Forest de-
cline continues to show a north-
south gradient, with Baden-Wurt-
temberg and Bavaria being most
hard hit with 64% damaged.
The symptomatology of decline for
each species of tree is dependent
on its site. A symptom common to
old spruce is extensive loss of older
needles, so that their crowns grow
thinner, Diseased young spruce in
some areas show a marked yellow-
ing of the needles, This is also
found in a less serious form on fir.
Crown thinning of fir goes along
with a reduction in apical growth
leading to formation of a so-called
Silver Fir
A typical symptom of damage
to fir is the premature development
of the so-called "stork s nest" crown.
Nowadays this phenomenon
is no longer found
exclusively in old trees.
The crowns of healthy fir trees,
in contrast, are extremely dense.
stork's nest crown. Entire branches
or parts of the crown die off in the
case of damaged beech. Autumn
coloration of foliage starts as early
as the end of June, and leaf-fall be-
gins in late summer.
Evaluating the results of the 1986
Forest Decline Survey requires re-
cognition that weather conditions in
Central Europe from 1984 through
1986 were favorable for growth of
trees, Nevertheless, the high de-
gree of damage persisted. Fortu-
nately, the 1986 survey showed that
slightly damaged trees, and in
some cases even more damaged
trees, have recovered somewhat,
Deciduous trees, initially thought 11
to be more resistant, now show a U
greater spatial extent of damage
than conifers. This increase in da-
mage is creating major problems for
the owners of forests who are trying
to create ecologically valuable
mixed stands. Beech, oak, and fir,
which particularly contribute to the
stability of the forest, cannot be re-
placed by other species.
31
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For years the worst enemies of the forest-dwellers were storms and snow, which caused a lot of damage particularly to
stands consisting solely of spruce. An aggravating factor in recent years has been the reduced development of the roots
of trees marked by "Waidsterben" which has led to further destabiiization.
Additional measures must be taken
to maintain the natural genetic re-
sources of these species, because
of the risk to fir and specific proven-
ances of other trees,
United States of America
In the eastern United States and
southeastern Canada forest decline
has been documented for high-ele-
vation red spruce and balsam or
Fraser fir in the North- and South-
east, for low-elevation (< 900 m)
red spruce and balsam fir in New
England as well as for loblolly and
slash pine in commercial forests of
the Southeast,
Several investigations show that
high-elevation red spruce has been
experiencing a decreasing growth
rate and significantly increased
mortality for 20 to 25 years at nu-
merous locations throughout the
northern and southern Appalachian
Mountains. The most common visi-
ble symptoms have been loss of
needles, premature senescence of
foliage, and decreases in fine-root
biomass.
Growth data for red spruce at low
elevations based on tree ring analy-
sis of increment cores indicate a re-
gionally consistent decrease in tree
basal area increment growth rates,
beginning around 1960. Unlike the
high-elevation situation where tree
core data are accompanied by visi-
ble symptoms and changes in
stand basal area, evidence of a pos-
sible decline at lower elevations is
available only from tree cores.
In the last years, dieback of sugar
maple in some regions of Quebec,
Canada, has become an issue of
some concern in Canada and east-
ern United States. Sugar maple die-
back is characterized by smaller
and paler leaves, gradual loss of fol-
iage, and peeling of bark from main
branches and trunk.
The fifth inventory of the Southern
commercial pine forests has recent-
ly been completed. This is a remea-
surement of timber inventory in the
five-state southeastern region (Flori-
da, Georgia, North Carolina, South
Carolina, and Virginia) in an approx-
imately 10-year cycle. By compar-
ison with growth rates and inven-
tory from the fourth survey, certain
changes in growth parameters con-
tributing to net annual growth were
noted.
32
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Most of these findings were con-
firmed by the observations of the
German-American group of experts
during their excursions through the
Appalachians in June 1984. The
U.S. Environmental Protection
Agency and the U.S. Forest Service
are cooperating in a major research
program to determine the spatial
extent and temporal development of
forest damage and its causes.
Measures
Fed. Rep. of Germany
The majority of experts now consid-
er that recent forest damage is a
"complex disease", initiated by the
combined effects of several stress
factors. Findings to date, however,
do not sufficiently meet the rigorous
requirements on data quality to be
able to define all the causes in con-
sideration precisely.
Despite the difficulty of providing
proof, at the end of the year 1984
the Research Council for Forest Da-
mage and Air Pollution named air-
borne pollutants and their deriva-
tives as major contributing factors.
This finding by the Council, together
with present research results, give
emphatic support to the legal mea-
sures proposed and initiated by the
German Federal Government for the
reduction of pollutant emissions.
The most important step to reduce
sulfur dioxide in the atmosphere
was the passing of regulations con-
cerning emissions from large fur-
naces, which went into effect on
July 1, 1983. These regulations also
call for the reduction of nitrogen
oxide emissions. Power plants and
district heating plants contribute
some 28% of total nitrogen oxide
emissions, and industry about 14%.
Heavy metal emissions will also be
reduced.
By 1988, with the help of these re-
gulations: it is planned to lower the
current level of sulfur dioxide emis-
sions by half from about 3.2 million
metric tons per year and to bring
the figure down to 1.2 million metric
tons per year by 1993.
A further important initiative is the
revision of the Technical Guidelines
for Air Pollution Control (TA-Luft)
which came into effect in March
1983. These guidelines set maxi-
mum values for pollutants from var-
ious sources, and ambient air quali-
Erosion
There is often severe erosion on
steep slopes. A healthy mountain for-
est of mixed species of trees pre-
vents erosion and protects against
rock fall. The reforestation of ava-
lanched slopes is often very expen-
sive: $ 500,000 (smallphoto above)
and $ 15,000 (below).
33
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These pictures of destruction
are rare in the Federal Republic of Germany,
and they cannot be attributed solely
to the effects of air pollutants.
Nevertheless, they serve as a warning
that the living conditions of forests must be improved.
34
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ty standards are established for the
most important air pollutants. These
regulations not only considerably
improve the protection of human
health, but for the first time provide
protection to sensitive plants and
animals, as well as food and fodder.
In the revision of these guidelines,
the standards for 15 substances
were lowered, some drastically, and
new substances were included for
control. To limit pollution further,
in July 1985 the Federal Cabinet
passed another revision of the
Technical Guidelines dealing with
emissions. This tightens the limits
for particulate emissions of, for
example, lead, cadmium, nickel,
mercury, cyanides, and fluorides, as
well as for organic compounds.
The introduction of new standards
will also considerably reduce emis-
sions of nitrogen oxides and other
pollutants from mobile sources. The
European norms set in 1985 for au-
to exhaust gases in environmentally
acceptable cars generally require
catalysts or other technical mea-
sures to reduce the emissions. In
the Federal Republic ot Germany,
the use of low-emission vehicles
and the introduction of unleaded
gasoline are being forced by a
whole series of measures. With ca-
talyst technology, pollutant emis-
sions from combustion engine can
be decreased by about 90%.
United States of America
As early as the 1940's it became
clear that air pollution was a serious
problem in the United States. In the
late 1940's, Los Angeles took mea-
sures to control its smog problem.
However, state and local govern-
ments were generally reluctant to
impose tough control requirements
which might cause industry to lo-
cate in another state. To control air
pollution more effectively, it became
necessary to develop a national ap-
proach.
In 1963, Congress passed the
Clean Air Act which authorized the
U.S. Public Health Service to study
air pollution and to provide grants
and training to state and local agen-
cies to control it. This legislation
was strengthened considerably
when the Clean Air Act Amend-
ments of 1970 were signed into law,
making the recently created Envi-
ronmental Protection Agency (EPA)
the focal point of the federal effort.
The 1970 amendments to the Clean
Air Act required EPA to set National
Ambient Air Quality Standards for
those airborne pollutants most
widespread throughout the country.
EPA has identified six such "criteria"
pollutants: ozone, carbon monox-
ide, total suspended particulates,
sulfur dioxide, lead, and nitrogen di-
oxide. For these pollutants, primary
standards are intended to protect
human health, and secondary
standards are meant to protect what
the Act refers to as "welfare", pri-
marily crops and livestock, vegeta-
tion, buildings, and visibility. For
some of these pollutants, one
standard has been set to protect
both health and welfare.
The Clean Air Act Amendments al-
so require EPA to review and regu-
late hazardous air pollutants. These
pollutants are defined as those that
can contribute to an increase in
mortality or in serious illness, but
which are not already regulated as
criteria pollutants. EPA is currently
analyzing a number of air pollutants
to determine whether they are ha-
zardous and require regulation. The
Agency already has issued stan-
dards for several pollutants: asbes-
tos, beryllium, mercury, vinyl chlo-
ride, radionuclides, and benzene.
Under the Clean Air Act, as amen-
ded, state and local governments
have primary responsibility for the
control and prevention of air pollu-
tion. EPA has the duty for setting
national standards to protect public
health and welfare, conducting re-
search on prevention and control of
air pollution, and providing technical
and financial assistance to state
and local governments for air pollu-
tion control. Each state must draw
up a State Implementation Plan
(SIP) describing how it will control
emissions from mobile and station-
ary sources in order to meet the
National Ambient Air Quality Stand-
ards (NAAQS).
EPA and state and local govern-
ments have taken a number of
steps to control air pollution Most
industries now have equipment in
place to reduce air pollution. New
cars are built to standards that re-
present a reduction of about 95%
for volatile organic compounds and
carbon monoxide and 75% for ni-
trogen oxides. Because the princi-
pal design changes made to de-
crease emissions require use of un-
leaded gasoline, a side effect of de-
sign changes has been significant
reductions in lead emissions from
mobile sources. Furthermore, the
United States has acted to limit the
amount of lead added to leaded ga-
soline. Emissions reductions from
mobile and stationary sources.have
resulted in considerably lower am-
bient levels of all the pollutants, and
far fewer communities now experi-
ence pollution levels exceeding
air quality standards. From 1970
through 1984 annual emissions of
sulfur dioxide in the United States
decreased about 24%. Nitrogen ox-
ide emissions rose about 9%, with
two-thirds of that increase occurring
during the first five years.
Responsibility
and Prevention
The development of forest damage
in the Federal Republic of Germany
has required politicians to take
quick and vigorous action for air
pollution control. What has been
done could not be based on hard
scientific evidence. The success of
these measures in protecting for-
ests is difficult to predict. Measures
must be taken in view of a grave si-
tuation, recognizing a responsibility
for preventive care. They will in ad-
dition benefit human health, plants
and animals, soil and water, monu-
ments and buildings. Developing
the necessary technology requires
high capital investment and also
places a financial burden on the in-
dividual citizen. But, saving the for-
est ecosystem as well as protecting
human health and welfare is surely
worth the effort.
A ckno wledgements
The authors would like to express their
thanks to Forstrat E. Aldinger (Univ. Frei-
burg), Prof. K.E. Rehfuess (Univ. Mu-
nich), Prof. F. Fuhr (Jiilich Nuclear Re-
search Center) for their critical review of
this manuscript and for many sugges-
tions. The authors would also like to
thank Dr. D. Bennett and Dr. C.J. Brandt
(U.S. Environmental Protection Agency)
for contributing the section on research
and measures in the United States.
35
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Cause-Effect Researc
Forest Decline
Major Research Efforts in the Federal Republic of Germany
and the Eastern United States of America
Forest decline is not an unknown
phenomenon. In earlier times it was
regionally limited. However, since
the end of the 1970's, a decline type
disease has spread all over Central
Europe and parts ot North America.
The recent forest damage in Central
Europe differs from earlier tree dis-
eases in that now there is concern
for the entire forest ecosystem. This
worrying development has alarmed
the general public and scientists in
the Federal Republic of Germany
and the United States. Consequent-
ly, authorities in both countries have
reacted with increased support of
research into the extent and causes
of forest damage.
Federal Republic
of Germany
In order to obtain well-founded
scientific data to help in making pol-
icy decisions to combat the causes
of forest decline, public institutions
have made considerable funds
available for research since 1982.
Initially, these activities were sup-
ported in parallel by the individual
States and the responsible Federal
ministries. To increase efficient use
of the available funds, the relevant
Federal and State ministries formed
an interministerial working group
(IMA). The IMA ensures coordina-
tion between Federal and State re-
search activities and makes possi-
ble the efficient planning, execution,
and evaluation of research projects.
This working group receives expert
advice from the Research Council
for Forest Damage and Air Pollution,
which is made up of 15 selected ex-
perts. Research institutes, such as
the German Aerospace Research
Establishment (DFVLR), the GKSS
Research Center Geesthacht, the
National Research Center for Radia-
tion and Environmental Research
(GSF), and the Nuclear Research
Centers at Karlsruhe (KfK) and
Jiilich (KFA), because of their spe-
cialized knowledge, have all taken
overworking and organizational
functions for Federal and State re-
search efforts. The Federal Environ-
mental Protection Agency (UBA)
and the German Research Founda-
tion (DFG) are also integrated into
this system.
In addition to ensuring that available
research funds are allocated effi-
ciently and without major adminis-
trative red tape, the coordination by
the interministerial working group is
designed to concentrate research
on selected sites and to promote in-
terdisciplinary studies within a
broad general concept. Since 1982,
many scientists from universities
and large research establishments,
as well as from industry, have
formed such interdisciplinary work-
ing groups. The emphasis of their
research is on selected regional
sites. In addition, research not res-
tricted to individual sites is being
done on transport, transformation,
and deposition of atmospheric pol-
lutants.
The Research Council for Forest
Damage and Air Pollution, as the
scientific advisory body of the IMA,
has the specific task of description
of the current state of knowledge
concerning forest damage research
findings, and indication of further
research needs.
In 1985, Federal and State govern-
ments, the German Research Foun-
dation, and other supporters pro-
vided DM 90 million for research on
the causes of forest decline in the
Federal Republic of Germany. This
sum was divided among more than
250 projects. The Federal Ministry
for Research and Technology con-
tributed DM 18 million in 1986.
United States of America
In the United States, the US Forest
Service of the Department of Agri-
culture and the US Environmental
Protection Agency (EPA) have long
been involved in research on the ef-
fects of air pollution on forest eco-
systems. The National Acid Precipi-
tation Assessment Program (NAP-
AP) was initiated in 1980 to investi-
gate not only the effects of acidic
precipitation on human health, ma-
terials, and aquatic ecosystems, but
also the effects of acidic precipita-
tion and the impact of air pollution
on American forests. A specific re-
search program on forest damage
was planned and financed within
NAPAP in 1984 by EPA, the Forest
Service, and the National Council
of Air and Stream Improvement
(NCASI) of the pulp and paper in-
dustry. In 1986, available funds to-
taled about $15 million.
In the forefront of these investiga-
tions is the question whether forest
damage is caused by acidic precipi-
tation alone, or in combination with
other pollutants. The interdiscipli-
nary working groups are conducting
research in four general forest
types: spruce-fir forests, southern
36
-------
Measurement of rain water flowing down a tree trunk. Because of the large filtering effect of the leal and needle surfaces,
the concentration of injurious substances from water on the trunk is much greater than in precipitation and throughfall.
This can result In root damage to the trees.
commercial pine forests, eastern
hardwood forests, and western con-
iferous forests. In 1984, field and
controlled laboratory investigations
have already begun on cause and
effect realtionships for spruce, fir
and pine. Experiments on other
species have been started in 1987.
Additional support for forest decline
research comes from meteorolo-
gists. A network of twelve monitor-
ing stations has been established in
the montane forests of the eastern
United States. These stations are
equipped to study chemical pro-
cesses in clouds, dry and wet de-
position mechanisms, and cloud
water deposition to forest ecosys-
tems.
The National Science Foundation
also supports long-term ecological
investigations designed to contri-
bute to knowledge of the effects of
atmospheric deposition. Studies
are being carried out in forest and
aquatic ecosystems to examine the
nutrient and heavy metal cycles,
weathering of bedrock, and reac-
tions of the hydrosphere to acid in-
put. The Electric Power Research
Institute (EPRI) supports research
on the influence of acidic precipita-
tion on nutrient cycles in forest eco-
systems, leaching of nutrients from
the soil, and responses of forest
and crop plants. Research spon-
sored by EPRI also considers the
interactions between tree crowns
and atmospheric pollutants.
37
-------
Portions of branches are placed in measuring devices, in order to measure
transpiration and photosynthesis rates of spruce. The measurements are made
under controlled conditions of air temperature and humidity directly at the site.
From the measured exchange rates for water vapor and carbon dioxide,
conclusions can be drawn concerning the regulation of the stomata of spruce
needles of different age classes.
Regional Centers
of Research
In the Federal Republic of Germany
and the United States of America,
research on cause-effect relation-
ships is being carried out in particu-
lar regions. There are four such re-
gions in the Federal Republic: nor-
thern sub-alpine mountains (Soil-
ing, Hils, Eggegebirge, Harz), nor-
thern Bavaria (Fichtelgebirge, Ba-
varian Forest), southern Bavaria
(Munich gravel plain, Calcareous
Alps), and southwestern Germany
(northern and southern Black For-
est).
In the northern mountains, the major
emphasis is on the relationship be-
tween deposition of pollutants, soil
acidification, and effects on soil bi-
ology and root developement. In the
Fichtelgebirge, research is concen-
trated on changes in soil chemistry
as well as on nutrition and physiolo-
gy of diseased trees. In the Bavari-
an Forest, main interest is on the fil-
tering of gaseous pollutants by the
forest canopy. Main topics of inter-
est in southern Bavaria are the fur-
ther development of remote sensing
methods in connection with terres-
trial surveys and the sulfur budget
of affected forest soils. Research in
southwestern Germany is investi-
gating the extent and effects of at-
mospheric pollutants, deposition,
stand nutrition, soil biology and
chemistry, the rhizosphere, and per-
colation water.
In the eastern United States, inter-
disciplinary research has been or-
38
-------
yj ¦
Large scale experiment
fwith already damaged
spruce in open-top chambers.
To measure the influence of airborne pollutants
directly at the research site,
the trees are exposed to polluted as well as to filtered air.
39
-------
ganized on sites in the Appalachi-
ans, The work is concentrated in
two regions: the northern Appala-
chians (Green Mountains, Adiron-
dacks) and the southern Appalachi-
ans (Mount Mitchell, Smoky Moun-
tains, Oak Ridge). In the northern
Appalachians, pollutant input, soil
chemistry, changes in forest vegeta-
tion, and extent of damage are be-
ing examined. Further emphasis is
on research into atmospheric and
cloud chemistry. On Mt. Mitchell re-
search is concentrated on investi-
gating the degree of damage, my-
corrhizae, and deposition of heavy
metals. Oak Ridge National Labora-
tory is involved in large-scale eco-
logical projects and investigating
the influence of atmospheric depo-
sition on bio-geochemical cycles in
forest ecosystems.
Description of Sites
Research results for several select-
ed sites in the regional centers of
research in the Federal Republic of
Germany and eastern United States
are presented in the following sec-
tions. The interpretation of the data
and the working hypotheses repres-
ent the views of the authors in each
case. Other scientists might offer
alternative explanations.
40
-------
Above:
Apart from damage to parts of the
tree growing above ground, there is
also damage to roots. The picture
shows a binocular examination of fine
roots. Here living fine roots are sepa-
rated from dead ones and their quality
is assessed. Later they are examined
for nutrient and pollutant content.
Left:
Experiments with young spruce in
a climate chamber. In these experi-
ments environmental conditions
are simulated, and the reactions of
the plant to stress situations are
observed.
Right:
Determination of the ion concentra-
tions in precipitation and in soli solu-
tion with a flow injector analyzer.
The principle of wet chemical analysis
enables the fast processing of a large
number of samples.
-------
Soiling
B. Ulrich and E. Matzner
University of Gottingen
Hannover
468
r • ^
Paderborn
GERMAN
' DEMOCRATIC
. REPUBLIC
Kassel ¦'
/ #528vn
Soiling
The Soiling is a mountainous region
between the rivers Weser and Leine
in the southern part of Lower Saxo-
ny. The region is gently rolling and
belongs to the Weserbergland. The
Grosse Blosse mountain reaches a
height of 528 m. The Soiling is one
of the largest forest areas in Lower
Saxony, with about 500 km2 of natu-
ral deciduous forest and conifer
stands established later.
Local Climate
The climate is montane and charac-
terized by large and widely varying
seasonal differences. The average
annual temperature is 6.5°C, and
the average annual precipitation
about 1050 mm Frequently, there is
fog in the winter months in the high-
er parts of the Soiling.
/ Beech
Spruce \
46% J
\ 410/0
/ 8 \5\/
Oak
Others
Relative areas of tree species in the
Soiling. The share of deciduous trees
is greater than that of conifers.
Current Forestation
and Potential
Natural Vegetation
The potential natural vegetation is
beech forest. This typical natural
forest has been replaced in some
areas by spruce forests as a result
of human intervention in the past.
Past Land Use
The Soiling forests were formerly
exploited because of the large tim-
ber requirements in the glass, por-
celain and iron industries. This
resulted in extensive deforestation
in the mid 18th century. At the be-
ginning of the 19th century a num-
ber of mines had to be closed, be-
cause the reserves of wood were
completely used up. Therefore,
Percentage Damage Category
100-
%
80 -
60-
40 -
20-
0
Spruce Others
Beech
large-scale reforestation was start-
ed in those days. Today, mining of
..Soiling slabs" of red sandstone,
the timber industry and tourism are
all economically important.
Soil Types
Geologically, the parent rock of the
Soiling mainly consists of different
layers of red sandstone. The soils
have developed from weathered red
sandstone and also from loess in-
cursions or, in some cases, from
overlayers of loess. The dominant
types of soil are brown earths. On
the plateaus, pseudogleys with var-
ying degrees of podzolization are
often found.
Forest Decline
According to the 1986 Decline Sur-
vey, 42% of the forest in the Soiling
are damaged. For the individual
species the picture is as follows:
Norway spruce accounts for 40.5%
of the wooded area of the Soiling,
and half are over 60 years old. Main-
ly these older trees are damaged,
whereby two-thirds are slightly
affected (damage category 1) and
a fifth show moderate damage
(damage category 2).
With 46%, European beech has the
largest share of the woodland, two-
thirds of which are over 60 years
old. A quarter of the young beech
and a third of older beech are slight-
ly damaged.
Oak covers 8.3% of the woodland,
with 60% exceeding an age of 60
years. While young trees are hardly
damaged at all, two-thirds of the
older oak show slight damage.
Right:
Forest decline in the Soiling in 1986; percentages of damage categories within
tree species. Spruce, beech and oak are slightly damaged. The older trees are
more affected than the younger ones. About a fifth of the old spruce shows
damage of category 2.
•*0
42
-------
bvfzi
1U--
Stand of 140-year-old beech in the Soiling shortly after coming into leaf. The ground vegetation consists predominantly of
young beech regeneration. This stand of natural and unfertilized woodland is located in an unmanaged area.
43
-------
Research Sites
in the
Soiling Area
Changes in
the Ecosystem
B. Ulrich and E. Matzner
University of Gottingen
State Forest (Soiling)
Norway spruce and
European beech stands
Aspect: plateau
Elevation: 500 m
Parent material:
loess and red sandstone
Soil types:
dystrochrept (podzolic brown earth)
Soil pH value: 3.0-4 0
Base saturation: < 5%
Stands
Composition:
100% Norway spruce
100% European beech
Age:
spruce: 102 years old
beech: 137 years old
Planted or natural regeneration:
spruce: planted
beech: natural regeneration
Past land use:
spruce: grassy heath
beech: managed forest;
litter was probably used
for potash production
Investigations have been conduct-
ed since 1966/68 in a 137 year-
old stand of European beech
(Fagus sylvatica)and a neighboring,
102-year-old stand of Norway
spruce (Picea abies). The stands
are located on a plateau about
500 m above sea level. The Norway
spruce developed following affor-
estation of former heath land. The
beech stand was probably used for
forage in the 18th century.
The stands grow on podzolic brown
earths which developed from loess
and red sandstone, laying above
weathered clayey red sandstone.
On both sites, the humus form is
a typical mold. The soils are very
acidic, as can be seen from the
change in pH value (CaCI2) with
depth and from the low base satu-
ration (< 5%) across the entire soil
profile.
Present
Research Activities
Most of the research projects in the
Soiling are being carried out by the
Institute for Soil Science and Forest
Nutrition of the University of Gottin-
gen. The main emphasis is on mea-
surements of the input, the retention
and reactions of persistent airborne
pollutants such as acids, heavy me-
tals and nutrients. Investigations are
also being carried out on the rela-
tive importance of natural and man-
made acid input, and the use of fer-
tilizer as a countermeasure The
program is rounded off by measure-
ments of microbial activity in the soil
and studies of stand nutrition.
Other groups (Silviculture) are in-
vestigating the fine root dynamics in
these plots. The Zoological Institute
is studying the influence of soil
acidification and fertilizers on soil
life It is planned to extend the exist-
ing program by including measure-
ments of air chemistry, physiologi-
cal parameters of plants, photosyn-
thesis and growth. The main spon-
sor for the research is the German
Federal Ministry for Research and
Technology.
Past
Research Activities
The following studies were carried
out in the Soiling area under the
topic ..causes of forest decline":
Input measurements
Major elements (since 1969):
Hydrogen ion, sodium, potassium,
calcium, magnesium, iron, manga-
nese, aluminum, sulfur, phospho-
rus, chlorine, ammonium and nitrate
ions, and total nitrogen input.
Heavy metals (since 1974):
Chromium, cobalt, nickeJ, copper,
zinc, cadmium, lead.
Organic compounds (1980/81):
Polycyclic aromatic hydrocarbons.
Output measurements
Major elements (since 1969 for
European beech and since 1973
for Norway spruce)
Heavy metals (since 1974)
~ 0
E
,= 20H
a
a>
a
o
CO
40-
60-
Beech
Spruce *\
3.0 4.0
pH-Value (CaCIa)
pH values (CaCl2) in the soil. The soils
of investigated European beech and
Norway spruce stands are highly acid-
ified.
Ecosystem balances
Major elements (since 1969)
Heavy metals (since 1974)
Protons (since 1969)
Measurements
of acidity pulses in the soil
(since 1981)
Measurements
on fine root processes
(since 1981)
Microbiological and zoological
investigations of the soil
in both fertilized and unfertilized
soils.
Analyses of foliage
These have been carried out at ir-
regular intervals since 1966 in all
areas, with intensification for beech
stands since 1981.
44
-------
t
Typical fog situation tor forests in mountain areas, with low overhanging clouds.
In the foreground is a vigorous 10 year-old Norway spruce with a very good
height and regular branching. In the background are damaged stands of older
spruce in an exposed position.
Fertilizer experiments
On European beech and Norway
spruce since 1973; intensified on
beech since 1981. The flow of all im-
portant elements is followed on all
sites.
Investigations of the nitrogen cycle
Investigations of growth
Chemical soil analyses
on all areas since 1966 at periodic
intervals, the last study being in
1983.
Element cycles
in forest ecosystems
By determining element flux balanc-
es for parts of the ecosystem or for
the system as a whole, the retention
of the input substances can be fol-
lowed and conclusions drawn on
their effect on the system.
Results for
the Entire Ecosystem
A summary of the results since 1966
relevant to forest decline is given in
the following sections.
Soil A cidification
Acid deposition (equivalent to 3.2 kg
per hectare and year for beech and
5.4 kg per hectare and year for
spruce) causes the leaching of cal-
cium (Ca), magnesium (Mg), man-
ganese (Mn), and aluminum (Al)
from the soil. With a very low base
saturation, aluminum is the cation
leached most. The aluminum con-
centration in the percolation water is
about 3 mg per liter under beech
and 15 mg per liter under spruce.
The acidification of the soil predis-
poses the stand towards deficiency
of calcium, magnesium and potas-
sium, thus increasing the risk of tox-
ic acidity in the root system.
Nitrogen Saturation
Spruce trees are not able to com-
pletely absorb the overabundant ni-
trogen. Nitrogen is washed out of
the soil as nitrate.
Reduced
Decomposition of Litter
In both experimental areas, the de-
composition of litter is reduced be-
cause of the lower activity of soil
bacteria and other microorganisms.
This results in an accumulation of
organic matter on the forest floor.
Damage Symptoms in
Individual Trees
Analysis of Annual Rings
A phase of increased radial growth
increment, nearly double the ex-
pected rate, ended in 1970 in both
spruce and beech stands. From
then on, annual ring widths again
approached the average figures
forecast in the yield tables. The
increased growth can mainly be
traced back to the input of nitrogen
into the ecosystem over a time peri-
od during which growth was not yet
limited by soil acidification.
Root Analyses
In 1969/70, both stands exhibited
high mortality of the fine root bio-
mass, from which they recovered.
This event can be traced to a pulse
of acidity in 1969, resulting from
nitrifrication and from soil acidifica-
tion following the deposition of ac-
ids. Measurements since 1981
show that the growth of fine roots is
determined by the chemistry of the
soil solution (acid toxicity). The re-
generation of fine roots does not
seem to be limited by the supply of
carbohydrates. The growth de-
crease of the trees is partly attribut-
able to the increased consumption
of assimilates in the root system.
Foliage
From 1971 to 1973 there was an in-
creased loss of needles which was
accompanied by snow breakage in
crowns of spruce. Many trees have
recovered. Yellowing symptoms
45
-------
CtJ
.c
CD
c
0)
o
c
o
o
c
o
c
%
X
(a)
Spruce
a
Open Land
1970
¦a—A
1975
1980
Spruce
en 80
c 60
Open Land
(b)
1970
1975
1980
05
-C
CD
50-
40-
Q. 30-
c
a)
g1 20-
I 10-
A A/x'-
/AJ\
Spruce
V
Beech
£±s\
r
(c) 1970
1 1
1975 1980
Monitoring Period
Various deposition rates in the Soiling:
(a) acid input; (b) total sulfur input; (c) total nitrogen input.
In the Soiling, input rates have been measured since 1969 in Norway spruce and
European beech stands, both as bulk precipitation and as total deposition. The
low rate of acid input and sulfur deposition in the dry years (1982/83) is notable,
as is the increase of nitrogen input over the entire observation period.
have been observed in some
spruce since 1980, increasing from
year to year. However, the trees of-
ten subsequently recuperated,
Changes
in the Ecosystem
The high input of airborne pollutants
in the Soiling is changing the eco-
system. This applies to acids, ni-
trogen and heavy metal inputs. In
1968 the amount of exchangeable
calcium at 0-50 cm depth in the
mineral soil of the spruce stand was
260 kg per hectare, and declined to
100 kg per hectare in 1983. The acid
input leads to increased soil acidifi-
cation, with a consequent loss of
nutrients from the soil and the ap-
pearance of toxic concentrations of
hydrogen ions, aluminum and other
metals in the soil solution. The toxic
soil conditions result in reduced life-
time of the fine roots. The resultant
increased turnover of roots leads to
reduced growth. Root damage also
makes the stand more vulnerable to
damage from other stress factors.
Acidification due to man-made influ-
ences is reinforced by the effect of
natural acidification pulses occur-
ring in warm and dry years. There is
a clear overlap of natural and man-
made stress factors in the soil.
In acid soils, acidification pulses
lead to variations in the pH value
and variations in the concentration
of aluminum. This creates a major
acid load in the soil, which can lead
to root damage.
The application of fertilizer has led
to a marked revitalization of the
stand. This can be seen in the im-
provement in soil chemistry, a re-
duction in the rate of fine root turn-
over, an increase in wood growth
and positive results in the analyses
of leaves and needles.
Excluded Stress Factors
Research on the causes of forest
decline in the Soiling is focussed
on the question of root damage.
The following stress factors can be
excluded in this context:
Drought
Excluded by measurements of soil
water content.
Lack of assimilates
Excluded by observation and inter-
pretation of the fine root biomass
46
-------
25-i
O)
£20-
c
0
+—•
— Beech
Spruce j
h I A |
CTS
*= 15-
c
0
0
Hi '/iI/Wa. f-
i • v ,i V % /*-
0 10-
E
i :
./U ! 1
1 ¦-
<
0
\a-a -j- -
1 1 1
1970 1975 1980
Monitoring Period
Concentrations of aluminum in percolating water in soil 90 cm under spruce and
beech stands. After 1976, the spruce stand showed a drastic increase in the
aluminum concentration of the percolating water.
and the root dynamics. Similarly,
massive primary damage to the as-
similating mechanism by noxious
gases is improbable.
Hypotheses and
Research Approach
Damage affects not only the trees
but the entire ecosystem and re-
lated systems such as the hydro-
sphere. The hypothesis explaining
the cause of the damage can
be summarized in five sequential
points:
accumulation of pollutants in the
ecosystem (acids, heavy metals,
organic compounds)
I
destabilization of the system by
acid toxicity (decomposers, roots)
I
more severe damage to the root
system as a result of acidity pulses
i
vulnerability of the stand to
other initiating stress factors
after root damage
I
die off as a result of initiating and
accompanying stress factors.
This hypothesis is based on the
measure of the load (deposition)
and accumulation of pollutants, the
measurements of soil acidification
and acidity pulses, laboratory ex-
periments on acid toxicity, determi-
nation of root turnover and the accu-
mulation of the organic top layer. It
is based on the measurements
made in Soiling on a continuing ba-
sis since 1966.
The ongoing research program is to
be supplemented by the following
studies:
Analyses of spring sap: ion status
and buffering behavior of the leaves;
measurements of photosynthesis;
periodic removal of spruce needles
and investigation of physiological
and nutritional parameters; wood
quality; measurements of the air
chemistry by the State of Lower
Saxony.
References
Ulrich, B. and Pankrath, J., (Eds.),
Effects of accumulation of air pollutants
in forest ecosystems. D. Reidel Publish-
ing Company, Doordrecht (1983).
Ulrich, B. (Ed.), Berichte des For-
schungszentrums Waldokosysteme/
Waldsterben der Universitat Gottingen,
Volume 2(1984).
Ulrich, B., Mayer, R. and Khanna, P.K.,
Chemical changes due to acid precipi-
tation in a loess derived soil in Central
Europe. Soil Science 130 (1980)
193-199.
Seibt, G., Die Buchen- und Fichten-
bestande der Probenflachen des Sol-
lingprojekts. Schriften Forstl. Fakultat
Universitat Gottingen 372 (1981).
Published by Sauerlander-Verlag,
Frankfurt.
Murach, D., Die Reaktion von Fichten-
feinwurzeln auf zunehmende Boden-
versauerung. Gottinger Bodenkundliche
Berichte 77(1983) 1-126.
Manion, P.D., Tree disease concepts.
Prentice Hall, Ingelwood Cliffs, NJ,
pp. 399(1981).
Matzner, E., Hiibner, D. and Thomas, W.,
Content and storage of polycyclic
aromatic hydrocarbons in two forested
ecosystems in northern Germany.
Zeitschrift Pflanzenernahrung und
Bodenkunde 144 (1981) 283-288.
Matzner, E., Annual rates of deposition
of polycyclic aromatic hydrocarbons in
different forest ecosystems. Water, Air
and Soil Pollution 21 (1983) 425-434.
Matzner, E„ Khanna, P.K., Meiwes, K.J.
and Ulrich, B., Effects of fertilization on
the fluxes of chemical elements through
different forest ecosystems. Plant and
Soil 74(1983) 343-358.
Matzner, E. und Ulrich, B., Raten der
Deposition, der internen Produktion und
des Umsatzes von Protonen in Wald-
okosystemen, Zeitschrift Pflanzenernah-
rung und Bodenkunde 147 (1984)
290-308.
47
-------
Hils and Eggegebirge
B. Ulrich, J. Gehrmann, B. Prinz* and G. Spelsberg**
University of Gottingen
*State Institute for Air Pollution Research, Essen
* State Institute for Ecology, Recklinghausen
¦ Hannover
Braunschweig
468
,1142
7 #528Vs
[Soiling
[Gottingen
GERMAN
DEMOCRATIC
REPUBLIC
100 km
The Hils is a part of the Weser-
Leine Mountains which lies north
of the Soiling and forms an ellipse
from northwest to southeast. The
greatest extent of this geological
dip is about 10 km. The peaks
reach heights of up to 470 m.
The Eggegebirge is the most west-
ern part of the Weser Mountains.
The Egge consists of wooded high-
lands running from north to south.
The east flank is steep, and the
west flank gentle. At the Velmerstot
site, the Eggegebirge reaches a
height of 468 rh.
Local Climate
In the investigated Hils area, annual
precipitation is between 750 and
950 mm, the annual mean tempera-
ture about 7.5°C.
Beech
49,5 %
14.5
Others
Spruce
Oak
Relative areas percentages of tree
species in the Lower Saxony part of
the Weser Mountains.
The predominant winds, over 50%,
are from the west. The first year
of the experiment was particularly
warm and dry. According to the
German Weather Service, the an-
nual mean temperature in 1983 ex-
ceeded the long-term average by
1.1 °C, while precipitaton was 75%
of normal.
The regional climate varies strongly
in association with topography. The
exposed Hils ridge has relatively
more cool days, much fog. more
frost and longer snow cover than
the protected hollows.
In the Eggegebirge, the average an-
nual precipitation is between 1000
and 1100 mm. The higher precipita-
tion compared to the Hils is due to
convective rain, since the Eggege-
birge forms the first highland after
Percentage Damage Category
*0
< 1
<2
+ 3
Spruce Oak
Beech Others
the low-lying Westphalian Basin.
The mean annual temperature in
the Eggegebirge is about 7.5°C.
The annual variation in air tempera-
ture, 16°C, is due to the influence
of the Atlantic maritime climate.
Potential
Natural Vegetation
The potential natural vegetation
near the ridges of the Hils would
be woodland of oak and beech
(Querco-Fageturn), and on the
slopes, various types of beech for-
ests (Luzulo-Fagetum).
The predominant potential vegeta-
tion of the Eggegebirge would also
be a Luzulo-Fagetum.
Past Land Use
Long-term over-exploitation by the
glass industry, grazing, and log-
ging, especially in the northwestern
part of the Hils mountains, has re-
sulted in severe degradation of the
ecosystem (succession of heath-
land) and helps to explain the cur-
rent dominance of spruce. This
newcomer was planted to replace
the natural vegetation and is now in
its third generation.
In the Eggegebirge, too, the original
beech forests have been used
up and almost entirely replaced by
spruce in the past centuries.
Soil Types
The Hils ridges consist of low-base
chalky sandstone. This weathers to
a fine sandy substrate on which var-
ious soil types have developed.
Blocky podzols predominate, with
deep-reaching acidity. The sub-
Right:
Forest decline in the Lower Saxony part of the Weser Mountains in 1986.
Half the deciduous trees and a third of the spruce are slightly or moderately
damaged.
100 -
°/o
80 -
60 -
40 -
20 -
48
-------
Typical landscape in the Hits mountains with damaged old spruce stand in the foreground.
strate is poor in clay content, but in-
fluenced by infiltrated loess sedi-
ments. It has developed to brown
earth podzols or podzol brown
earth soils.
In places, the ridges of the Hils flat-
ten out to form a plateau, and there
is only a gentle slope down to the
interior hollow of the Hils. The sand-
stone there is mixed with appreci-
able amounts of loess and this in-
itial material leads to formation of
podzol brown earths. The deeper
horizons partly show weak pseu-
dogley formation.
On the slopes on the side of the
inner Hils hollow, the sandstone
gives way to flame marl. Here soli-
fluidic material prevails, which as a
rule is infiltrated by loess. The soil
develops to acid brown earths and
para-brown earths, which, in the
A-horizon, shows clear signs of
podzolization. Podzols in a medium
stage of development are frequently
found.
The ridges of the Eggegebirge are
formed by low-base chalky sand-
stones. These have developed into
podzols of various degrees. The
soils on the west slope are also lo-
ess influenced. The predominant
type of soil here is brown earth. On
the lower, flatter parts of the south-
ern Eggegebirge there is more
moisture and stagnogleys deve-
loped in some areas. The east
slope consists of various Jurassic
and Triassic formations.
Forest Decline
In the Hils mountains, damage is
mainly found on spruce on all west-
ern-exposed slopes and ridge
areas. Stands on the less exposed
side and in the interior hollows gen-
erally show only slight decline.
In 1984, which was a relatively cool
year with high precipitation, a small
but noticeable improvement was
observed.
As for the Lower Saxony part of the
Weser Mountains, the Forest De-
cline Survey of 1986 indicated slight
damage to 34% of the trees, moder-
ate to 10% and severe damage to
2%. The affected species are beech
and oak with slight damage of 46%
and 32%, respectively.
49
-------
Research Sites in
the Hiis Mountains
Comparative
Studies of Spruce
Stands Exposed
to Different
Pollution Levels
B. Ulrich, G. Wiedey
and J. Gehrmann
University of Gottingen
The contour map gives the loca-
tions of the investigated stands
where new sampling plots were es-
tablished during 1983 for input/out-
put measurements of major and
trace elements. In some of these,
extensive sampling has been done,
which has been coordinated be-
tween all the working groups in-
volved. The experimental design,
with varying sites and trees differing
in vitality from heavily damaged to
showing no symptoms, allows a
comparison of forest ecosystems
with different degrees of stress and
destabilization.
The predominant types of soil on
the ridges are rocky podzols. In the
extensive A-horizons of these soils
the base saturation amounts to
about 10% of the cation exchange
capacity (CEC). Aluminum accounts
for 30 to 70% and strong acids (iron
and protons) for 15 to 55% of
the CEC. In the organic top layer
(OH layer) the base saturation
(6-12%) is also low. The mineral
soil of such profiles (pH value
3.0-4.0, base saturation 5%) is
practically free of roots. In these cir-
cumstances, the organic top layer is
effectively the last refuge for the
roots. It is occupied mainly by long
roots, and only sporadically by
short feeder roots.
To a lesser degree, podzolic brown
earths with a large amount of humus
are found on ridges. This higher
proportion is also reflected in the
greater effective cation exchange
capacity and an increase in the ni-
trogen content of the soil solution.
The root system in these profiles is
strikingly concentrated in the pod-
zol-B-horizons.
On the slopes of the Hils basin
some acid brown earths and para-
brown earths have developed. The
chemistry of these soils can be de-
scribed with regard to the A-horiz-
ons in terms of the reactions of the
aluminum/iron buffer range. The dif-
ferences from the ridge soils are fre-
quently found below depths of
20-40 cm. In particular, the soil so-
lution is less acidic (pH value of the
soil solution in equilibrium, base
saturation and acid/base ratios). In
the solid phase the base saturation
is also very low ( <5%). However,
here the main root area in the min-
eral soil has been preserved, and
young trees are seeking a foothold
there. On sites where the soil is
characterized by flame marl, greater
amounts of potassium are found in
the mineral soil.
Research Activities
The research program covers long-
term evaluation of forest ecosys-
tems, damage characteristics, as
well as integrated investigations of
trees showing no symptoms (from
vital stands) and deteriorated trees
(from damaged stands). In addition,
individual processes are being in-
vestigated and various experiments
are being carried out. The objective
Geological layers of the Hits mountains and the locations of reference sites on windward and leeward sides. This design
allows a comparative study of forest ecosystems with different deposition rates of airborne pollutants. Section 103 is the
damaged, wind-exposed stand of young spruce, while the reference stand (sect. 65) on the lee side is healthy. The da-
maged stand of old spruce (sect. 109) is located on the windward side, while the reference (sect. 79) is inside the basin.
Upper 1 Ragstone
Cretaceous 2 Cenomanian
Lower 3 Flame marl
Cretaceous 4 Hils sandstone
5 Wealden
6 Neacomian
Upper Jurassic
Middle Jurassic
Lower Jurassic
7 Serpulite
8 Mund marl
9 Corallian colite
10 Ornate clay
11 Dogger
12 Lias
13 Muschelkalk
Sect. 109
Geological Layers
50
-------
S^Bwl
Ridge Site in the
Hi/s Mountains
A remarkable difference
can be seen between
spruce stands on the wind-
ward and leeward sides.
The high deposition rates
lead to strong acidification
of the soil on the side ex-
posed to the wind, as well
as high loss of needles
and root damage. Thus
bare patches form, on
which newly planted young
spruce are already show-
ing symptoms of forest
decline.
Old Spruce
Damaged spruce, exposed
to wind (left) and shel-
tered, symptom-free com-
parable trees (right). The
difference is clearly visible.
i\ \^L \ *£4^^
bdr/
'^mvV
/ fi: ^A.., \ ¦ -J ,
Young Spruce
Bs '-flSfV-' r'
Branches from damaged
spruce exposed to wind
(left) and from sheltered
comparable spruce without
decline symptoms (right).
The damaged branch
shows dear signs of chlor-
osis and stunted growth.
MMti T--,.., _
'% m^SLmlk fH
S 0 *
51
-------
is to provide as complete a picture
as possible of the stresses present,
and to study their effects on the eco-
systems and organisms. Based on
the available evidence, long-term
chains of cause and effect that de-
velop over decades cannot be ex-
cluded, and, indeed, attempts are
being made to identify such long-
term processes
The emphasis of the research is cur-
rently on integrated and interdiscipli-
nary studies on spruce showing da-
mage and on those free of symp-
toms. In 1983, studies began on old
spruce and in 1984 on younger
ones. The working groups involved
in these research projects are from
the fields of botany (morphology,
histology, physiology, biochemistry),
soil science and forestry (soil chem-
istry, water and elemental cycling of
the ecosystems, input rates of air-
borne pollution, output analysis),
biometry (growth pattern of the
trees), forest utilization (wood quali-
ty), forest growth (increment studies),
zoology (soil life, insects) and pa-
thology (fungus diseases, viruses,
etc.).
Young Spruce:
Comparison of
Stands on Windward
and Leeward Sites
Two neighboring stands of young
spruce were compared, one being
on the lee side, one to windward.
The damaged young spruce stands
(section 103) are exposed to the
wind, and the undamaged stand
(section 65) is on the lee side. The
damage was clearly quantifiable in
May 1983 in terms of needle loss
and discoloration (section 103: 93%
of trees damaged, section 65: 92%
free of symptoms).
With respect to the development of
damage over time, anatomical and
morphological investigations re-
vealed no visible damage of mer-
istematic tissues or of buds. Dis-
turbances during sprouting of the
lateral buds (April/May) can be ex-
cluded. During the period of shoot
growth (May to August) only minor
needle damage was observed. The
stunted shoots found are attribut-
Root system of a damaged 14-year-old spruce. There is remarkably little
branching of the roots. They are found only in the organic top layer of the soil.
Because of the strong acidification of the soil, no root growth in the mineral
soil is observed.
Young Spruce Stands
to Windward and
on the Lee Side (Hits)
States of health:
windward: section 103 exposed to
wind: 93%damaged
leeward: section 65 sheltered:
92% free of symptoms
Aspects:
windward: southwest slope on the
outer side of the ridge
leeward: northeast, inside slope
Elevations:
windward: 375 m: leeward: 320 m
Parent materials:
windward: Hils sandstone
leeward: loess - Hils sandstone
Soil types:
windward: podzol
leeward: podzolic brown earth
Soil pH values (H20):
windward: 3.1 -3.3
leeward: 3,8-4.7
Base saturations:
windward: 5% (up to 20% on
account of surface
application of lime)
leeward: 5-10%
Stands
Age:
windward: 14 years old
leeward: 14 years old
Planted or natural regeneration:
windward: planted
leeward: planted with about
5% of natural beech
regeneration
Past land use:
windward: spruce forest (second
generation) following
a heath ecosystem
leeward: pure beech stand
52
-------
able to above-average growth. The
increase in height is noticeably less
in damaged trees, but its course
shows no deviations from the nor-
mal pattern. Needle damage starts
in August and continues until the
new shoots sprout in spring. Before
they fall, the needles become disco-
lored, going from yellow and brown
to red. This can lead to a total loss
of needles and ultimately tree mor-
tality.
A comparison of the proportions of
living and dead fine root biomass
supports the hypothesis that spruce
trees react to increasing soil acidity
with a change in the allocation of
assimilates. The growth of wood in
the trunk region is reduced in favor
of a more rapid rate of root replace-
Otd Spruce Stands
to Windward and
on the Lee Side (Hits)
States of health:
windward: section 109 exposed to
wind: damaged
leeward: section 79 sheltered:
free of decline symptoms
Aspects:
windward: west-exposed slope on
the outer side of the ridge
leeward: gentle slope inside the
basin
Elevations:
windward: 460 m; leeward: 230 m
Parent materials:
windward: Hils sandstone
leeward: Flame marl
Soil types:
windward: podzolized brown
earth - podzol
leeward: podzol - brown earth
Soil pH values (H20):
windward: 2.7-4.3
leeward: 3.2-4.9
Base saturations:
windward and leeward: 5-15%
Stands
Age:
windward: 105 years old
leeward: 111 years old
Natural regeneration or planted:
windward and leeward: planted
Past land use:
windward: spruce forest (second
generation) following
a healh ecosystem
leeward: spruce forest
(second generation)
ment. The damage to roots found in
deteriorated trees parallels the in-
crease in soil acidity, so that toxic
acidity is probably a predisposing
stress factor. An analysis of nutrient
content indicates a lack of nitrogen,
and particularly of potassium. This
potassium deficiency is partly
caused by shallow rooting, which is
restricted to the organic top layer.
During the growth period the larger
amount of living fine root biomass in
the damaged stand compared to
the undamaged site indicates that
root dieback cannot be due to in-
adequate carbohydrate supply from
the needles. The abcission of nee-
dles in young spruce is caused by
dessication of the needles, i.e. it is
purely mechanical. Needle discolor-
ation prior to dessication indicates
that there are other stress factors
apart from water stress (the direct
effect of airborne pollutants such as
sulfur dioxide, ozone, acids, and
perhaps microorganisms). The low
potassium levels may also reduce
tolerance to drought. According
to published results it can be as-
sumed that in the damaged stands
the symplastic water transport in the
roots has practically ceased as a re-
sult of acid toxicity, which changes
the permeability of the cell walls.
Water uptake through the cell walls
of roots occurs behind the apical
meristem (the actively dividing cell
layer), where the xylem (conducting
vessels) is differentiated, but not the
endodermis.
Because of damage caused by the
acidic soil solution to the apical
meristem, the fine roots are prob-
ably short-lived, so that they are
perpetually being reformed under
constant consumption of assimi-
lates. This demand for assimilates
can only be covered during the
growth period. This interpretation is
consistent with the finding that da-
maged trees are less able to buffer
acidity deposited in the canopy.
Since uptake of calcium and al-
kaline substances (calcium com-
pounds with anions of weak acids)
occurs through the roots (apoplas-
matically), it may be concluded that
the lack of buffering ability indicates
difficulties during the uptake of cal-
cium.
The data from 1984 still being ana-
lyzed should provide further infor-
mation on the progress of the da-
mage and the validity of the hypo-
thetical explanation. It is hypothe-
sized that there is a disturbance of
the mycorrhization of the short roots
(i.e. the symbiosis of soil fungi and
roots). This is confirmed by the
completed mycorrhizae studies.
Old Spruce:
Comparison of
Stands on Windward
and Leeward Sites
Two stands of old spruce are being
compared. The damaged stand
(section 109) is on a slope exposed
to wind, while that free of damage in
1983 (section 79) is sheltered from
the wind. Increment studies showed
a 27% decline in growth of the da-
maged stand over the last decade.
This reduction is significant, consid-
ering that over the same period the
undamaged stand showed above
average growth. This is attributed to
the increased atmospheric deposi-
tion of nutrients and nitrogen in vital
stands, The growth reduction of the
damaged trees may be explained
by three causes:
• decrease of photosynthetic rate
• increase in respiration rate
• increased turnover of assimilates
in the root system.
The increased turnover-rate of as-
similates in the root system is ex-
plained by the efforts of the da-
maged tree to maintain the biomass
of its fine roots despite their short
lifetime, which is caused by the toxi-
city of aluminum ions. Investigations
in the Eggegebirge and Hils moun-
tains on old and young spruce
stands show that the increased
consumption of assimilates is of
considerable significance. Disturb-
ances to mycorrhizae, including a
high proportion of intracellular infec-
tions, have been observed. Analy-
sis of the starch content of the roots
provided no evidence of a lack of
assimilate supply.
Similarly, analysis of the needles for
chlorophyll content, permeability of
the cuticula for electrolytes, bleach-
ing of pigment, the accumulation of
starch and other physiological and
biochemical parameters relevant to
vitality provided no evidence of any
direct major influence of airborne
pollutants on the needles that could
possibly be responsible for differ-
ences in foliage area. Even in da-
maged trees, the green needles
-------
show no indication of their physio-
logical activity being affected. These
findings support the hypothesis that
needle damage is a short term
phenomenon caused by decline in
tree vitality as a result of root da-
mage accompanied by simultane-
ous exposure to airborne pollution.
The damage of small and fine roots
increases with deterioration of the
tree. From test results on the chemi-
cal condition of the soil and roots, it
appears that the damage may be at-
tributed to acid toxicity.
In reference to water supply, the
studies indicate a lower proportion
of live sapwood that can transport
water, an irregular sapwood-heart-
wood boundary, and a lower mois-
ture content in the sapwood of da-
maged trees. Measurements with a
gamma sonde confirm irregular wa-
ter flow in the trunk cross-section.
On the other hand, there is no evi-
dence of a lack of function of needle
stomata. Aside from possibly in-
creased (cuticular) transpiration, the
burden on the water supply is more
likely to be derived from difficulty in
water uptake than from excessive
transpiration. This also indicates
primary damage to the roots.
A similar picture emerges for old
spruce as for young spruce. The
root damage is soil induced, and
has been in effect for a long time,
acting as a predisposing stress fac-
tor. Apparently, water stress contri-
butes significantly to the damage of
the tree. The direct influence of air-
borne pollutants is obviously limited
to that of an inciting stress factor.
Based on present evidence, no ne-
gative effects on the mechanical
technological qualities of the wood
can be attributed to the influence of
air pollutants. "Forest damage" is
therefore not the same as "wood
damage". Nevertheless, there may
be economic loss because the
growth rate of deteriorated trees is
greatly reduced in some cases.
Excluded Stress Factors
The physiological and biochemical
investigations on green needles
from damaged and healthy trees
lead to the conclusion that the di-
rect influence of airborne pollutants
has not led to permanent damage
to the physiology of the needles or
to their capability for photosynthe-
sis. Rather, they seem only to da-
mage the needles when the tree vi-
tality has already been weakened
by some other stress factor.
Working Hypothesis
The research is based on the hypo-
thesis that forest decline is caused
by multiple stresses affecting the
ecosystem as a whole as well as
individual organisms. With such
stress-caused diseases, a distinc-
tion is made between predisposing,
inciting and accompanying stress
factors.
Predisposing Stress Factors
Climate
(heat, moisture, wind, etc.)
Site
(aspect, soil, etc.) - It determines
the elasticity of the ecosystem.
Genetic type
(hereditary factors)
Chemical climate
(airborne pollutants)
Si/vicu/tural management
The theory of ion cycles suggests
that in warm years they are affected
not only by water stress but also by
acidity pulses. This theory was con-
firmed by measurements. Thus the
effect of warm and dry years such
as 1975/76 and 1982/83 can no
longer be attributed solely to water
stress or ozone damage. There is a
need to determine whether acid
stress in the soil was also involved.
There is a link via acid stress be-
tween the effects of climate (acidity
pulses), silvicultural management
(acidification caused by land use)
and site (deposition rate, buffering
capacity of the soil). The develop-
ment of this theory and the neces-
sary measuring techniques to quan-
tify it have, in principle, been con-
cluded.
To determine the effects of deposi-
tion of airborne pollutants, element
balances have been established for
a number of forest ecosystems in
the areas of the Soiling, around
Gottingen, of the Hils and of the
Luneburg Heath for spruce, beech,
pine and oak. In these areas, the in-
put rates were determined for acids,
salts, nutrients and some selected
heavy metals. From the balances, it
can be determined where the depo-
sited substances remain and what
the relationships are between sinks
and sources (e.g. chemical reac-
tions of the deposited acids).
These studies confirm the present
picture of the extent and effect of ac-
id and nutrient input. Taken together
with the soil chemistry of these
sites, they clearly indicate that on
most of the sites investigated the
soils have lost their storage function
of nutrient cations (e.g. calcium,
magnesium, potassium). This pro-
cess was already partly completed
in the 1960s for magnesium and cal-
cium, and in the case of potassium,
is now nearing completion. It may
be expected, therefore, that as well
as the lack of absorbable calcium
and magnesium, there will soon be
a large scale potassium deficiency.
A framework has been developed
containing the various soil and root
chemistry parameters needed to as-
sess acid stress (toxic acidity). The
research results have confirmed
and quantified the chain of effects:
acid deposition
I
soil acidification
1
acid toxicity
Within the ecosystems examined,
this chain is probably of decisive
importance for the decline in tree vi-
tality.
Inciting Stress Factors
Extremes of climate
(Frost, drought, acidity pulses)
Extremes of chemical climate
(episodes of high concentration of
airborne pollutants such as sulfur
dioxide, nitrous oxide and ozone,
as well as acids; salt spray)
Leaf-eating insects
Mechanical damage
Acidity pulses can become inciting
stress factors leading to root da-
mage. Studies of spruce showed
that woody roots have a long histo-
ry of mortality symptoms, which
must have arisen in several damage
periods. In respect to seasonal
dymanics of fine root biomass, the
following could be excluded as
causes of reduction: Endogenous
rhythms (by comparing various
stands), soil temperature (of signif-
icance, however, for the beginning
of root growth), water stress and
54
-------
A predisposing stress factor: climate - red spruce deformed by wind.
An inciting stress factor: extremes of climate - frost damage to red spruce.
lack of assimilates. The fine root bi-
omass changes in parallel with the
degree of acidity of the soil solution,
which in turn depends on seasonal
acidity pulses and recovery phases.
Damage to the fine root system
must be seen as a dynamic pro-
cess of dieback and regeneration.
From results to-date, it appears that
fine root biomass is only affected
when there is a high degree of
needle loss (over 50%), while the
rate of root mortality and turnover
increases with higher needle da-
mage.
Accompanying
Stress Factors
Parasites
(e.g. insects, fungi, bark beetles,
cancerous fungi, fungi causing root
and wood rot, also needle fungi)
Bacteria, viruses, nematodes
The damaging effect of accompany-
ing stress factors extends to soil or-
ganisms, soil vegetation and trees.
Research Approach
The research approach attempts to
disentangle the complex factors in
the chain of causes and effects via
measurement and observation of
the various stress factors, to devel-
op criteria to assess them, and to
follow up and measure the damag-
ing effects on various species within
the ecosystems. Gaps still existing
in the approach will be closed. The
largest gap is the absence of con-
tinuous measurements of airborne
pollutants at the sites, It will be im-
proved by including the research
sites in the Lower Saxony air quality
monitoring network. To a limited ex-
tent, this research approach will al-
so be used to examine the cause of
damage to beech and pine. The
hypotheses derived from study of
the ecosystems will be thoroughly
checked in specific experiments.
References
B. Ulrich (Editor), Berichte des For-
schungszentrums Waldokosysteme der
Universitat Gottingen (Selbstverlag),
Vol. 2,3 and 4 (1984).
Manion, P.D, Tree disease concepts.
Prentice Hall, Ingelwood Cliffs, NJ,
399 p. (1981).
A predisposing stress factor: site conditions - spruce with stunted growth.
55
-------
Research Site:
Preufiischer
Ve/merstot
(Eggegebirge)
Damage to
Norway Spruce
B. Prinz and G. H. M. Krause
State Institute for Air
Pollution Research, Essen
Ve/merstot (Eggegebirge)
Aspect:
hills in north-south direction
Elevation: about 450 m
Parent rock:
Gault- or Neocom-sandstone
Soil type: podzolic brown earth
Soil pH value (CaCI2): 2.4-3.0
Base saturation: 0.3-0.9%
Stand
Composition:
mixed forests, mainly Norway spruce
Age: 13-82 years
Planted or natural regeneration:
planted
Past land use: unknown
Concentration
of pollutants per m3 in 1986
Sulfur dioxide:
Eggegebirge: 38 ng Ruhr area: 56 ng
Nitrogen dioxide:
Eggegebirge: 21 fjig Ruhr area: 50 [xg
Ozone:
Eggegebirge: 51 ng Ruhr area: 23 iig
Particles:
Eggegebirge: 46 |o.g Ruhr area: 60 ng
In September 1982, novel forest de-
cline was first observed in Nor-
thrhine-Westfalia in the Eggege-
birge, 150 km northeast of the Ruhr
industrial center and 80 km west of
the border of the German Demo-
cratic Republic. The Velmerstot site
is situated on a west-facing slope at
an altitude of 450 m. The mixed
stand is composed mainly of Nor-
way spruce of different age classes.
The soil type is podzolic brown
earth developed from gault or neo-
com-sandstone. Base saturation,
waterholding capacity and pH value
of the soil are low.
Research Activities
The State Institute (LIS) chose this
area as a regional center of forest
field research. As the decline situa-
tion of German forests is strongly
associated with the impact of air
pollutants, three major projects are
under current research:
• characterization of pollutants
in ambient air, including meteo-
rology
• effects of wet and dry deposition
on Norway spruce in open top
chambers
• characterization of local differ-
ences in deposition within a
small forested area.
Pollution
Monitoring Network
A telemetric air pollution monitoring
network was established in 1977
and presently consists of a total of
66 automatic monitoring stations.
The majority, 63 stations, are set up
in the center of the Rhine - Ruhr
region. Since 1983, three of these
stations are also operating at forest
sites in the Eggegebirge, the Eifel
and the Rothaargebirge. All the
stations are directly connected to a
central computer at the State Insti-
tute (US).
The results of these measurements
showed that the air pollution situa-
tion at the forest stations differs
significantly from that in the Ruhr
area. The burden of sulfur dioxide,
suspended particles, and nitrogen
dioxide is distinctly lower at the Vel-
merstot site. However, during the
winter months, when the wind
comes from easterly directions
(i.e. German Democratic Republic
and Czechoslovakia), high concen-
trations of sulfur dioxide can occur.
Concentrations of nitrogen oxide
are generally well below 10 |ig
per m3, and this is most likely the
reason why ozone concentrations at
the forest stations exceed those in
the Ruhr area by a factor of more
than two. During summer, monthly
means of ozone greater than 100 ng
per m3 have been observed.
800-
600-
3
"O
O)
O)
J±
U)
~ 400 H
O
03
0)
_J
E
3
CO
-------
Branches of damaged spruce in the Eggegebirge. All the older needles show
yellowing, a typical symptom of magnesium deficiency.
Open-top chambers
Yellowing of older needles of Nor-
way spruce and silver fir is one of
the most prevalent decline symp-
toms and is caused by acute mag-
nesium deficiency. The lack of mag-
nesium, appearing only in very
recent years, occurs in nearly all
mountain regions of the Federal Re-
public of Germany and other Euro-
pean countries and increases with
altitude. A depletion of magnesium
and calcium in soils by acidic wet
deposition as well as the impact
of air pollutants on above-ground
plant parts, mainly of ozone, are
currently being discussed as possi-
ble causes.
Laboratory experiments at the State
Institute (LIS) have shown that
ozone in combination with acidic
wet deposition increases leaching
of magnesium and calcium ions
from foliage. In order to test these
results in the field, an experiment
with eight open-top chambers was
set up at the Velmerstot site. Half of
the chambers are supplied with am-
bient and the other half with char-
coal filtered air. Each chamber con-
tains six Norway spruce. They have
a height of 1 m and show early
symptoms of magnesium deficien-
cy. Trees were transplanted from a
natural site in the vicinity and grow
in original soil.
In order to elucidate the role of acid-
ic wet deposition all chambers are
equipped with a lid and receive eith-
er natural or artificial rain. Growth
measurements are carried out dur-
ing spring and fall in order to deter-
mine tree reactions to the various
treatments. It is expected that the
data gained over a five year period
will lead to a better understanding
of the major influencing factors
causing forest decline.
Deposition Studies
Measurements of pollutant concen-
trations in ambient air as well as of
deposition rates are carried out in a
30 -year-old spruce stand located at
Velmerstot. Three sampling plots
have been installed at 1.5 m above
ground inside, at the edge, and out-
side the forest. Two plots were esta-
blished in the vertical axis at 12 and
18 m height in the crown area and
above the canopy, respectively,
This program was started in 1986. It
is planned to collect data over a pe-
riod of three years. The first results
show gradients of pollutant concen-
trations in ambient air along the hor-
izontal and vertical axes from out-
side to inside the stand and from
below to above the canopy, respec-
tively. The other parameters (depo-
sition data as well as pH value, con-
ductivity and element concentra-
tions in collected water samples) al-
so show gradients from outside to
inside the stand. More information
on the processes of deposition and
effects of air pollutants causing
forest decline is expected after a
detailed analysis of all data.
Conclusions
Based on measured data and ex-
perimental findings to date, the fol-
lowing hypothesis is proposed:
Forest decline in mountain regions
is caused by a depletion of magne-
sium and calcium in soils by acidic
wet deposition as well as the impact
of air pollutants on above-ground
plant parts, mainly by ozone. The
ozone concentrations increase with
altitude, similar to deficiency symp-
toms on trees. Ozone is highly phy-
totoxic and injures cell membranes,
leading to increased permeability,
so that vital nutrients, like magne-
sium, are leached more easily. This
increases the potential for nutrient
deficiencies. By this process, trees
become predisposed to other biotic
and abiotic stress factors, whereby
climate seems to be of major im-
portance as a synchronizing factor.
References
Krause, G.H.M., Prinz, B., and Jung,
K.D., Forest effects in West-Germany.
In: D.D. Davis (Ed.), Air Pollution
and the Productivity of the Forest,
pp. 292-332, Washington, 1983.
Krause, Arndt, U., Brandt, C.J.,
Bucher, J., Kenk, G. and Matzner, E.,
Forest decline in Europe: Development
and possible causes. Water, Air and
Soil Pollution 31 (1986) 647-668.
Pfeffer, H.-U., Immissionsmessungen in
Waldgebieten des Eggegebirges und
der Eifel. In: Forschungsergebnisse zur
Problematik der neuartigen Waldscha-
den. LIS-Berichte der Landesanstalt fur
Immissionsschutz des Landes Nord-
rhein-Westfalen 57 (1985) 43-72.
Pfeffer, H.U, and Buck, M,, MeBtechnik
und MeBergebnisse von Immissions-
messungen in Waldgebieten.
VDI-Bericht 560(1985) 127-155.
Prinz, B., Ozone effects on vegetation.
In: NATO advanced research workshop
on tropospheric ozone. Regional and
global ozone and its environmental con-
sequences. Lillehammer, Norway, 1987.
57
-------
Harz
M. Hauhs, P. Benecke and B. Ulrich
University of Gottingen
The forests of the Harz mountains
cover an area of over 2000 km2.
About half of the Harz is in the Fed-
eral Republic of Germany, while half
belongs to the German Democratic
Republic. The highest point of the
Harz, the Brocken, reaches a height
of 1142 m. The Harz arose in the
Permian Era by the Hercynian fold-
ing together with the Central Massif
in France, the Rhineland Schist
Massif and the Bohemian Forest.
The Harz is in the northeastern part
of these central mountains. It rises
steeply from the North German
Plain and provides the first major
obstacle for the west winds sweep-
ing over it.
/ Spruce \
78% \
\ A \ /
18 X
Others^ —Beech
Relative areas of tree species in the
Harz. Norway spruce dominates with
a share of 78%.
Local Climate
The Harz is characterized by a sub-
atlantic climate. The high precipita-
tion is evenly distributed over the
year. The snow cover in winter is
frequently interrupted by periods of
thaw. Ground frost occurs very sel-
dom, when snow-free ground is ex-
posed to very low temperatures.
Current Forestation
and Potential
Natural Vegetation
Originally, Norway spruce was
found only at the highest altitudes.
European beech predominated over
Percentage Damage Category
100
%
80
60
40
20 H
0
-<1
*2
Spruce Others
Beech
Right:
Forest decline in the Harz in 1986; percentages of damage categories within
tree species, in the predominant variety of Norway spruce about one-third is
slightly damaged and one-fifth moderately damaged.
Hannover
Braunschweig
..1142
Gottingen
GERMAN
DEMOCRATIC
REPUBLIC
the rest of the Harz, with other de-
ciduous species depending on the
base content of the soil and the lo-
cal climate. Today the Harz is
stocked almost solely with Norway
spruce.
Soil Types
The Harz has rocks rich in bases
(diabase, gabbro) as well as rocks
with the lowest base content (quart-
zite, flinty slate). The majority are
sandstones with a medium rich
base content and clayey slate.
There is also the granite massif of
the Brocken and its surroundings.
Rich and poor rocks are frequently
mixed during downslope transport.
Brown earths are predominant, but
because of over-exploitation and
acid deposition, they are very acid
and low in nutrients. The humus
form is from mold to coarse humus.
The brown earths are partially pod-
zolized and podzols have also
formed on the lowest based rocks.
Past Land Use
The Harz region is old, with a strong
mining tradition once associated
with gold and silver, today with zinc,
lead and barium oxide. The Harz
forests have been changed much
because of the timber requirements
of mining and smelting industries.
This began as early as the year 500.
It reached its peak from the 15th to
the end of the 19th century. In the
neighborhood of the mines smoke
damage resulted in some areas los-
ing all their ground vegetation, with
58
-------
The hills and valleys in the Upper Harz are mostly wooded. While the Norway spruce in the foreground seems to have little
damage, severely damaged individual trees can be seen in the background.
the surface of the soil being eroded
right down to the bedrock. At the
end of the 17th century the Harz
was already largely deforested, and
planned reforestation began with
Norway spruce (Picea abies, Karst ).
About 1800, storm and bark beetle
damage led to further deforestation
of the Harz.
Forest Decline
The West German part of the Harz
comprises 78,400 hectares of for-
est. The 1986 forest survey showed
that 33 % of the total forest area
was slightly damaged, 17% moder-
ately, and 2% severely damaged.
Together with the coastal area of the
North Sea, the Harz has the highest
degree of forest damage in Lower
Saxony. The situation is especially
critical in the Upper Harz.
In the 1970s, the northwestern Harz
was severely wind-damaged, so
that today wide grassy slopes may
be found with meagre plantations of
spruce. Examination of the older
and present root patterns lead one
to conclude that many trees were
blown down following root damage.
59
-------
Research Site:
Lange Bramke
Catchment
An Ion Budget
Study
M. Hauhs and B. Ulrich
University of Gottingen
Lange Bramke (Harz)
Aspect: north and south slopes
Elevation: 540-700 m parent
Parent material:
Lower Devonian sandstone
Type of soil:
cambisols and podzols
Soil pH value:
(H20): 3.4-4.7 at 0-60 cm depth
Base saturation:
2-4% in the root area
Stand
Composition:
100% Norway spruce (Picea abies)
Planted or natural regeneration:
planted
Past land use:
3rd generation of spruce;
formerly a natural stock of beech
Known disturbances:
1947 clear-cutting of the precious
stock (at that time 140 years old)
The research site at Lange Bramke
is located in the Upper Harz. The
catchment is covered by a 30 to 38
year-old stand of Norway spruce
(Picea abies, Karst.) planted after a
complete clearcut in 1947. Its size is
76 hectares and it ranges in eleva-
tion from 535 to 700 m. The valley is
stratified into two north- and south-
facing subcatchments. The bedrock
is a lower Devonian (Kahteberg)
sandstone containing a mixture
of quartz and muscovite (Sericite).
Residual soils with a content of up
to 60% of stones have a total depth
of about 3.5 m at midslope of the
cross-sections investigated. The
soils within the catchment are cam-
bisols and podzols, the latter occur-
ing on the ridges. The mean annual
temperature is 5.8°C and the preci-
pitation averages 1303 mm, equally
distributed over the year
The previous stand of 140 year-old
Norway spruce (Picea abies, Karst.)
was completely cut down in 1947.
At that time hydrological research
on the consequences of the excep-
tionally large clearcut was started.
Research continues, resulting in a
40 year record of runoff and precipi-
tation. Since 1977, investigations al-
so have been focussed on the ion
budgets of the soils and the catch-
ment. Therefore, continuous mea-
surements have been available be-
fore and after forest decline oc-
curred at the Lange Bramke water-
shed. This is a unique situation.
Forest Decline
As the Harz mountains are one of
the best documented examples of
forest decline in the Federal Repu-
blic of Germany, the relation be-
tween the catchment and its geo-
graphic region will be briefly dis-
cussed. Damage to Norway spruce
in the Harz mountains is of two
types with clear differences in their
regional distribution.
The first type of symptoms involves
yellowing of the upper surfaces of
two year-old and older needles ex-
posed to the sun. This yellowing is
caused by magnesium deficiency of
the foliage. It can result in needle
loss that starts from the inner and
moves to the outer portion of the
crown. It occurs in the Harz mainly
on 40-60 year-old trees on sand-
stone and granite. The Lange
Bramke catchment lies in the center
of the area where this decline type
appears. Here in 1982, the first trees
with yellowing were observed and
by 1984 one third of the population,
mainly the dominant trees, was af-
fected. In 1986 basal area growth
reduction was described for affect-
ed trees.
The second type of decline symp-
toms is characterized by loss of
green and brown needles. This
starts either at the outer parts of the
crown or spreads throughout the
crown. It is possible to distinguish
between these two symptoms by in-
frared aerial photography, because
no yellowing is involved in this type
and the patterns of needle loss are
different. Such a regional mapping
showed that the second type of de-
cline is concentrated on older trees
(> 60 yrs.), which grow on the
poorest bedrock (quarzite and grey
wacke) and often in wind-exposed
locations. The more unspecific
symptoms of the second type
spread gradually during the last de-
cade and at the Lange Bramke it oc-
curs on the wind-exposed ridge of
the south-facing slope.
The data from the Lange Bramke
catchment can be used to discuss
possible links between acid deposi-
tion, soil sensitivity and indirect ef-
fects on the forest. The sandstones
of Lange Bramke represent a typical
situation of the Harz. Because of
large variation, however, rocks with
much higher or poorer content of
calcium and magnesium silicates
occur. Acid deposition at Lange
Bramke is high with 46 kg of sulfur
per hectare and year in relation to
other sites in Central Europe or
North America. In the Harz moun-
tains it represents the minimum, be-
cause of its wind sheltered position
and the young stand. Brookwater at
the weir has 250 micro-equivalents
per liter of sulfate ions. That is less
than almost any other stream in the
Harz mountains.
Experimental Design
Acid deposition may gradually
change the exchangeable nutrient
pools in forest soils. An assess-
ment of such a change involves the
measurement of ion fluxes and
pools. The experimental set-up and
the research concept for studying
water and ion budgets are portray-
ed in the illustrations. In 1977, eight
60
-------
The Lange Bramke watershed in the northwestern Harz is an idea/ area lor studying the imbalance o! a forest ecosystem.
South Slope
. Rooting Zone
<*&8o°o-Qc A
•a °0o %V
' o ® Q • • /» Ofif, o r iWbnh ItWiw
ikii2'>Po*?0» o'-*> - &SWPA
Rooting Zone 3
impermeable
Layer
The concept of ion budgeting
applied to a slope cross-section
in the Lange Bramke watershed.
The input via precipitation and
through tail as well as the
total output are measured.
Vertical seepage beyond
the root zone allows
calculation of Ion fluxes
In seepage water.
With flux data from
three Independent
measurement levels
over a period of eleven years,
this is one of the
oldest budgeting studies
in the Federal Republic
of Germany.
611
-------
monitoring plots were installed on a
crosssection of the watershed with
four plots on each of the major
slope aspects. Each of these plots
was equipped with throughfall sam-
plers, suction lysimeters and ten-
siometers. Snow depth and snow
water equivalent are monitored at
30 locations. Measurements at the
two mid-slope locations ceased in
1979. In 1986 a new plot was in-
stalled on the exposed ridge of the
south-facing slope.
Model for Water Flow
Ion fluxes in the soil can be derived
from measured soil water chemistry
and calculated seepage water rates.
The water fluxes within at least the
first 100 cm of the sloping soils at
the Lange Bramke are identified as
vertical, unsaturated seepage. A de-
terministic model was used to cal-
culate their fluxes.
This finite element model calculates
the distribution of the pressure
head in the cross-section of the wa-
tershed and the runoff from given
daily infiltration and potential trans-
piration rates. The results of model
runs from 1978 until 1981 agreed
with measured daily sums of runoff
at the weir and the soil matric pot-
ential from various locations along
the cross-section.
Results
Most of the sulfur and hydrogen ion
deposition occurs at the Lange
Bramke watershed outside the
vegetation growing period. The long
term average of wet deposition is al-
most identical to results from the
Soiling area. Throughfall levels un-
der the spruce stand at the Lange
Bramke, however, are only 50% of
the fluxes measured at a compar-
able research site with Norway
spruce in the Soiling. This differ-
ence is probably due to the fact that
the 105 year-old spruce at the Sol-
ling are older and that the Soiling
site is more exposed to cloudwater
interception than the sheltered val-
ley of the Lange Bramke.
The spruce stand at the Lange
Bramke extends to an exposed
ridge, where throughfall measure-
ments began in 1986. Here the
fluxes of all ions are substantially
higher than those measured within
the same stand at the base of the
slope.
Flux measurements of total deposi-
tion, seepage, and runoff reveals
that transport of sodium and chlo-
rine through the Lange Bramke
catchment is conservative. In addi-
tion, the concentrations in the
stream of the mobile anions of chlo-
rine, nitrate (and sodium) can be
calculated from the soil solution
measurements at the north- and
southfacing slopes as well as at the
ridges. In contrast to that, 50% of
the sulfate flux in throughfall is re-
tained in the catchment soils.
Flux measurements of calcium and
magnesium indicate net export from
the soil. Most of the calcium and
magnesium export at the weir
stems from storages beyond the
rooting zone. A number of soil sur-
veys are available to evaluate the
consequences of this negative bud-
get for base cations such as mag-
nesium and calcium.
A comparison of soil inventories in
1974 and in 1984 show a decrease
of exchangeable calcium and mag-
nesium within the upper 70 cm of
the soil. Soil solution analysis from
1977 to 1985 yielded decreases in
calcium and potassium at the plot
that had the highest values in 1977,
whereas the magnesium concentra-
tions remained low at all plots. From
the fluxes of major ions in precipita-
tion, throughfall, seepage, and run-
off it can be concluded that soil
acidification is progressing at the
Lange Bramke watershed.
Surface Waters
In 1985, exchangeable base cation-
concentrations were measured from
the surface to bedrock at 3.5 me-
ters. The depth profiles of calcium
and magnesium can be interpreted
as transient stages of the current
base cation depletion. There is no
net export of potassium from the
catchment, but it may be involved in
the sulfur retention in subsoil horiz-
ons (0.8-3.3 meters). The dominant
anion in throughfall, seepage, and
runoff is sulfate from atmospheric
deposition, Thus, the base cation
depletion of calcium and magne-
sium is caused in the upper soils
partly, and in the lower soils mainly
by acid deposition.
The net export of calcium and mag-
nesium from the catchment may
stem from an exhaustion of the ex-
changeable pools of these ions or
from silicate weathering. The rate at
which the zone of base cation de-
pletion will proceed in depth (and
thus towards surface waters) de-
pends on the relative importance of
these two processes.
Soil Acidification
and Forest Decline
The ratios of calcium to aluminium
(Ca/AI) and magnesium to alumini-
um (Mg/AI) in the soil solution at
80 cm depth dropped by about 50%
during the last ten years. These ob-
served changes in soil acidification
parameters coincided with the de-
velopment of forest decline symp-
toms at the Lange Bramke water-
shed. The Ca/AI and Mg/AI ratios
fell below their critical values for nu-
trient uptake within that period of
time. Foliar analysis of trees affect-
ed by yellowing showed magne-
sium deficiency. Two year-old nee-
dles contained only 0.17-0.43 mg
of magnesium per gram (dry wt.)
and 1.0-2.6 mg of calcium per
gram (dry wt.).
The gradients of acid deposition,
soil chemistry, and decline symp-
toms across the catchment allow
discussion of the relationship be-
tween soil acidification and the two
observed decline symptoms. Three
examples are given below listing
those items which differ significantly
At the southfacing slope the plot is
severely affected by yellowing. It
shows the highest standing bio-
mass, but the lowest amount of or-
ganic matter in the humus layer
(65 tons per hectare . The fine root
biomass is concentrated in the min-
eral soil (> 70%). As nitrate is be-
low the detection limit in all eight
suction lysimeters nitrogen is com-
pletely retained within the ecosys-
tem. Seepage water volume is the
lowest (and transpiration rate the
highest).
The plot at the ridge was first affect-
ed by needle loss and, since 1986,
also by some yellowing. The plot at
the northfacing slope is almost with-
out visible symptoms but a recent
needle inventory showed that the
trees have one needle age class
less than those on the southfacing
slope.
The northfacing slope and the ridge
are discussed together, because
they differ only in acid deposition
62
-------
Damaged Norway spruce on the south-facing slope of the Lange Bramke.
The older generations of needles are affected by intense yellowing. Analysis of
the discolored needles shows extremely low magnesium contents.
and in the ionic strength of the soil
solution (both higher at the ridge).
On these slopes, fine roots are con-
centrated in the humus layer
(> 80%) that contains more than
120 tons per hectare in dry weight.
Nitrate leaching equals or exceeds
throughfall levels. On the northfac-
ing plot, where bimonthly measure-
ments are available, nitrate in-
creased by a factor of 3 since 1977.
This increase was paralled by a rise
of the aluminium concentrations.
Soil chemical changes due to acidi-
fication cannot be excluded as the
critical stress factors in both decline
types. We hypothesize that the dif-
ferences listed above have deve-
loped due to variations in the initial
soil chemistry and in the internally
produced acidification of the grow-
ing spruce stand.
On the south-tacing slope, the fine
root system has only been slightly
affected and is still able to maintain
water and nitrogen uptake. Here,
the exchangeable magnesium pool
in the soil becomes the limiting fac-
tor. At the other two plots the most
likely limiting factor seems to be wa-
ter stress. Decreased water and ni-
trogen uptake is reflected in the
lower growth rates and in the un-
specific needle loss symptoms.
Higher nitrate concentrations have
been measured on the north-facing
slope of the Lange Bramke and the
nearby catchment of the Dicke
Bramke. At both watersheds, the
relative largest increase in runoff
concentrations of nitrate ions was
observed at the end of the growing
season. This clearly shows the link
to the decreasing uptake in the de-
clining stand. When nitrate satura-
tion (input equals output) is reach-
ed, the seasonal pattern of nitrate in
runoff disappears.
Conclusions
A recently developed hypothesis
explains why the two types of forest
decline symptoms, yellowing and
needle loss, are occuring under
spatially different deposition re-
gimes. The development of the
magnesium deficiency symptom of
older needles should be restricted
to acid deposition levels relatively
moderate for the Harz. Because of
the large scale north-south gra-
dients in acid deposition across
Germany the same deposition le-
vels are also typical for sites in
Southern Germany. The surveys
carried out by infrared aerial photo-
graphy showed such trends for the
distribution of the two symptoms,
needle loss and yellowing.
To our knowledge this is the first hy-
pothesis that is able to integrate the
evidence from process level re-
search and the gradients in acid de-
position and forest decline in the
Federal Republic of Germany.
References
Hauhs, M., A model of ion transport
through a forested catchment at Lange
Bramke, West Germany. Geoderma
38(1986) 97 113.
Hauhs, M., Water and ion budget of a
forested catchment at Lange Bramke
(Harz) (in german). Berichte des For-
schungszentrums Waldokosysteme/
Waldsterben Bd. 17, Gottingen 1985.
Hauhs, M., The impact of forest decline
on surface water quality (in german).
Zeitschr. Dt. Geol. Gesellsch. 136(1985)
585-597.
Hauhs, M. and Wright, R.F., Regional
pattern of acid deposition and forest
decline along a cross section through
Europe. Water, Air, and Soil Pollution
31 (1986) 463-475
Hauhs, M. and Dise, N., Depletion of
exchangeable base cations in an acid
forest soil at Lange Bramke, West Ger-
many. Geoderma (submitted).
Dise, N. and Hauhs, M., Sulfate reten-
tion characteristics of an acid forest soil
at Lange Bramke, West Germany. Geo-
derma (submitted).
G3
-------
Fichtelgebirge
W. Zech
University of Bayreuth
In northeastern Bavaria, on the
Czech frontier, are the wide, mas-
sive peaks and ridges of Palaeozoic
mountains, such as the Bavarian
Forest, the Oberpfalzer Wald, the
Fichtelgebirge, and the Franken-
wald. The highest elevation in the
Fichtelgebirge is the Schneeberg,
with a height of 1051 m.
Geomorphologically, this is atro-
poidal insular range which was ex-
posed to deep weathering with re-
sultant pediment formation in the
Tertiary. Large deposits of Kaolinite
were formed from parent rocks
(granite, gneiss, phyllite, shists),
which today are the basis of the
northern Bavarian porcelain indus-
try. During the Quaternary, forma-
tion of deeply incised valleys and
solifluid soil erosion occurred. The
result on the one hand are com-
pacted solifluction covers on the
slopes and on the other, bizarre
rocky labyrinths exposed on the
summits (Kosseine near Wunsie-
del).
Local Climate
The Fichtelgebirge forms the wa-
tershed between the Atlantic and
the Black Sea. In addition, it repres-
ents a climatic boundary. Thus the
more westerly exposed slopes, in-
cluding summits such as the
Schneeberg, the Ochsenkopf and
the Waldstein, have a pronounced
Atlantic climate with average annual
precipitation of 1000 to 1200. mm
and mean annual temperatures be-
tween 4.5 and 6.0°C. The eastern
parts, in the area of the "Selb-Wun-
siedler Bight", on the other hand,
are continental in character (aver-
age annual precipitation 600 mm,
cold winters with icy east winds and
a short vegetation period). There
are up to 200 days per year with
fog. The main wind directions are
west (30%), northwest (17%) and
southwest (13%). Because of their
topographic and geomorphological
characteristics, the Fichtelgebirge
present a major barrier for the pre-
dominant west and east winds, but
also for air streams from the north
and south. This might be important
regarding forest decline.
Spruce
5 10
Beech Pine & Larch
Relative areas of tree species in the
Fichtelgebirge. Spruce covers 85% of
the forest area.
Right:
Percentage
100-
%
80 -I
60
40-
20-
Damage Category
>«0
•«1
<2
«3
Spruce Deciduous
Fir
Forest decline in 1986 in the Fichtelgebirge, the Frankenwald and Steinwald;
percentages of damage categories within tree species. Two-thirds of spruce are
slightly and moderately affected. More than half of Scots pine show decline.
Current Forestation
and Potential
Natural Vegetation
Spruce (Picea abies)dominates in
the higher parts of the Fichtelge-
birge, while in the Selb-Wunsiedler
Bight there are also extensive
stands of pine (Pinus sytvestris),
e.g. the „Selb pine", noted for its ex-
cellent quality and shape.
Fir and beech are less evident in
these forests today. However, this
was not always the case. In the nat-
ural forests of former centuries, they
were frequent. But after the exten-
sive lumbering that started in the
Middle Ages, after industrialization
mining and glass production start-
ed, the natural vegetation of beech
GERMAN
DEMOCRATIC
REPUBLIC
Karlsbad ¦
Bayreuth")"
¦ Regensburg
100km
64
-------
View of the Ochsenkopf. Measurements at the University of Bayreuth show that ambient pollutant concentrations can be
particularly high in fog droplets. The pH values in fog water can be as low as 2.5.
and fir was largely decimated. It
should be mentioned that in the ex-
tensive reforestation that took place
in the 19th century, mainly non-local
provenances of spruce were plant-
ed. These varieties are particularly
susceptible to breaking under
snow. It is not yet known whether
these non-local provenances
are more susceptible to damage
caused by air pollution.
Soil Types
At lower elevations mainly acid
brown earths with low nutritive value
have developed from acidic rocks
such as granite, gneis and phyllite.
At higher elevations podzols occur
with thick layers of mor. Apart from
transitional forms between brown
earths and podzols, hydromorphic
soils, like gleysols, can be found.
Eutrophic brown earths also occur
on Tertiary basalts, which are parent
material in a few places
Nearly all soil profiles show stratifi-
cation: topsoils are fragile and in-
tensively rooted. In contrast, the
subsoil is compacted and hardly
susceptible to roots, and the long
axes of the rocks are parallel to the
slope surface.
Forest Decline
Since early 1980, increasing forest
decline phenomena have been ob-
served in all tree species. For in-
stance, in the period 1983-84 the
area of Bavaria with no previous
signs of damage declined by 10%
to 43%, while moderately damaged
stands increased by 13%. Particu-
larly marked decline occured in the
Fichtelgebirge, the Frankenwald
and Steinwald. The Forest Decline
Survey of 1986 found the following:
More than 70% of the spruce
stands, which cover 85% of the for-
est area in the Fichtelgebirge, show
damage. One third of all spruce is
slightly damaged, another third is
moderately damaged and 2% are
severely damaged or already dead.
In pine, which only covers less than
10% of the area, damage is less
marked (55%).
65
-------
Research Activities
Research Sites: Oberwarmensteinach,
Wiilfersreuth and Se/b (Fichtelgebirge)
Site-Specific Damage to Norway Spruce
W. Zech, R. Horn, M. Kaupenjohann, and R. Hantschel
University of Bayreuth
The research site of Oberwarmen-
steinach is situated on a west-fac-
ing gentle ridge of the Fichtelge-
birge at an altitude of 700 m. The
site of Wulfersreuth is on a gentle
west-facing slope at 670 m, and that
of Selb on a northeastern exposed
slope at 560 m. The soils at all three
sites are either podzolic or eutro-
phic brown earths, respectively, de-
rived from metamorphic rocks such
as phyllite and basaltic solifluction
Oberwarmensteinach
(Fichtelgebirge)
Damaged stand
Aspect: west-facing ridge
Elevation: 700 m
Parent rock:
phyllitic solifluction material
Soil types:
Spodosols and Inceptisols
Soil pH value:
surface layers: about 3
below: about 4
Base saturation:
1% in mineral soil
Stand
Composition: pure spruce stand
Age:
30 to 40 years old, 90 year old
spruce in the adjacent stands
Planted or natural regeneration:
planted about 100 years ago, but
recently natural regeneration
Past land use:
under management for about
100 years
Known disturbances:
needle tip chlorosis since 1982;
bark beetle attack in 1983
covers. At the three sites the current
vegetation is primarily Norway
spruce, about 30 to 40 years old.
Originally, the forests were mixed
stands of Norway spruce, European
beech, and silver fir or mixed decid-
uous trees at Selb. These forests
were largely cleared during the Mid-
dle Ages. Systematic silvicultural
management has been carried out
only for the past one hundred years.
Wulfersreuth and Selb
(Fichtelgebirge)
Healthy control stands
Aspect: gentle middle slopes
Wulfersreuth: west-facing
Selb: northeast-facing
Parent rock:
Wulfersreuth: phyllitic solifluction
cover
Selb: basaltic solifluction
cover
Soil types: Brown earth
Wulfersreuth: podzolic
Selb: eutrophic
Soil pH value:
Wulfersreuth: 3-4
Selb: 4-5
Stand
Composition:
pure spruce stand
Age: 35-40 years old
Planted or natural regeneration:
planted
Past land use:
under management for about
100 years
Known disturbances: none
Severe damage to Norway spruce
was only observed at Oberwarmen-
steinach. Why this was not the case
for Wulfersreuth and Selb is the
subject of on-going research. The
research activities involve:
• measurement and balance of
nutrient and water flux
• determination of amount and
reactivity of buffering substances
in the soil
• quantification of water supply,
rates of transpiration, and photo-
synthesis of both damaged and
healthy spruce
• investigation of bonding states
of ammonium ions (NH4) and
interactive relationships to nitrate
production
• determination of the influence
of magnesium-based fertilizers
on tip chlorosis of spruce and on
soil conditions.
The German Federal Ministry for
Research and Technology is sup-
porting these activities of interdis-
ciplinary working groups from the
University of Bayreuth and the Tech-
nical University of Munich. Addition-
ally, the Bavarian Ministry of Culture
is financing some twenty related
projects on specific aspects of pol-
lutant deposition, plant physiology,
and soil science. These activities
are combined in the research pro-
ject "Forest toxicology".
Decline Symptoms
The characteristics of spruce de-
cline are tip chlorosis of older nee-
dles and increasing crown transpar-
ency. This yellowing of spruce was
first observed on a large scale in
1980 at altitudes above 700 m.
Hardly any healthy spruce may be
found at locations above 900 m.
This chlorosis indicates magnesium
deficiency. Similar symptoms of
magnesium deficiency were found
on silver fir and larch. Deciduous
European beech and mountain ash
developed chlorosis and necrosis
of the leaf tips and margins. In ex-
treme cases beech leaves have de-
veloped intercostal chlorosis and
necrosis. Foliar discoloration ap-
pears to be more pronounced on
trees exposed to sunlight.
66
-------
Spruces of all age classes show the yellow tip chorosis above 700 m. This is a yellow discoloration of the tips of two-year
old and older needles. The yellowing is more pronounced on twigs which are exposed to the sun and closer to the ground,
respectively. Recent needles are green and generally unaffected. Bark beetle attack and snow breakage may finally lead to
death of the entire stands.
Results to Date
Comparative studies were carried
out on fertilized and unfertilized
plots at Oberwarmensteinach,
Wulfersreuth and Selb. The most
important results up to now are as
follows:
Six-month old needles of the first
whorl of chlorotic spruce always
contain less magnesium than nee-
dles of the same age from healthy
green trees. The magnesium level
of damaged spruce is about
0.6 grams per kilogram of needles
or less. Application of magnesium-
rich fertilizer led to an increased
magnesium content of 0.9 grams in
the first year. This level increased
during the following three years up
to 1.4 grams per kilogram There
has also been a noticeable im-
provement in the magnesium con-
tent in older needles.
Control
1000 kg MgS02
- 1.2
1.0H
E ^
S 0.5 H
££
CT)
g
2
10000 kg MgO
+CaC03
0-I
SelD
a— Wulfersreuth
o
Oberwarmensteinach
I I
F
2.7
r
1.7 0.7
I
0.7
2.7 1.7
Needle Age [years]
2.7 1.7 0.7
Magnesium content of spruce needles originating from fertilized and unfertilized
plots at the research sites of Selb, Wulfersreuth and Oberwarmensteinach as a
function of needle age class. The magnesium supply of the stands at Oberwar-
mensteinach is insufficient. Therefore, fertilization results in a doubling of the
magnesium contents of recent and older needles. A faster reaction is observed
after fertilization with magnesium sulfate than with a combined magnesia-lime
fertilizer. This may be attributed to different solubility of fertilizers. Spruces of the
base rich Selb site do not react on fertilization, while at Wulfersreuth the magne-
sium content of older needles increases.
67
-------
Relative to the foliage of healthy
trees, recent needles of the first
whorl of damaged spruce are gen-
erally poorer in calcium and zink.
This fact also holds for manganese,
although its level is still relatively
high (300 to 2000 ng per kg of nee-
dles).
In most cases nitrogen and phos-
phorous supplies are good and
excellent, respectively. However,
potassium levels are sometimes
found to be below 0.45 grams per
kilogram of needles, so that in
some cases potassium deficiency
might occur.
The photosynthetic rate of chlorotic
spruce is lower than that of healthy
spruce, but there is no evidence of
water imbalance in spruce.
Soils at Oberwarmensteinach and
Wulfersreuth are acidic: the pH va-
lues (CaCI2) are between 3.0 and
3.3 in the surface layers, and reach
4.0 in the subsurface layers. In the
eutrophic brown earth at Selb, the
soil pH value of all horizons is about
one unit higher. Accordingly, base
saturation in the soil at Selb is sub-
stantially higher (90 %) than at the
other sites, where base saturation
sinks below 3 % in the mineral hor-
izons. In addition, amounts of ex-
changeable calcium and magne-
sium are extremely low. From this
perspective, there appears to be no
significant difference between the
soils at Oberwarmensteinach (char-
acterized by chlorotic spruce) and
Wulfersreuth (healthy green spruce).
However, Oberwarmensteinach is
unique among the sites with healthy
spruce in respect to the molar rela-
tionship of water-soluble magne-
sium and aluminum. This difference
is less distinct in the equilibrium soil
solution.
The representative soils at both
sites have potentially good aeration
and are adequately supplied with
water available to plants. Because
of their texture and structure, large
variations may occur in their nutrient
and water cycles. Fertilization with
magnesium oxide and calcium
carbonate stimulated microbial ac-
tivity and decomposition of organic
material.
In 1984, sulfur inputs were 32 kg per
hectare in Wulfersreuth and 36 kg
per hectare in Oberwarmenstei-
nach. For comparison, the average
annual sulfur input is between 20
and 25 kg per hectare in the well-
known Soiling area of northern Ger-
many. The sulfur deposition rates
found in throughfall at the damaged
site of Oberwarmensteinach are
about 35% higher than those mea-
sured at Wulfersreuth. One possible
explanation for this difference could
be that Oberwarmensteinach is lo-
cated on a ridge, whereas Wulfers-
reuth is located at mid slope.
Although magnesium nutrition of
spruce growing on the unfertilized
plot at Oberwarmensteinach was al-
ready poor, precipitation during the
second half of 1984 also resulted in
leaching of some 0.5 kg of magne-
sium per hectare from the needles.
At Wulfersreuth no leaching was ob-
served. Improved nutrient supply
due to fertilization simultaneously
led to higher losses of magnesium
by leaching (e.g. 1.2 kg per hectare)
on a plot fertilized with magnesia
(MgO) at Oberwarmensteinach.
Damaged Stand
Control Stands
0-
20-
e
r 40 H
Q.
O)
Q 60 H
o
W 80-|
100-
0.01
Oberwarmen-
steinach
T
T-
0.05 0.1 0,5
Molar Ratio of Mg2 + /AI3'1
Wulfersreuth
i
1.0
10
Molar ratio of magnesium and aluminium in perculation water extracts (1:10) of
the soils from the sites of Oberwarmensteinach, Wulfersreuth and Selb. The ion
ratios of the soil extracts of the declining stand at Oberwarmensteinach are one
(top layer) to two orders of magnitude (lower layers) smaller than those of the
healthy stands of Wulfersreuth and Selb. This is a measure for the low amounts
of plant available magnesium at the Oberwarmensteinach site.
Left:
From the results obtained it can be concluded that damage to spruce, which is
characterized by yellowing, only occurs on extremely acidic soils. The pH values
(CaCI2) decrease to 3.0 in the upper soil horizons and rise with depth to about
4.0. Below the organic top layer an extremely leached horizon can be seen
followed by a so-called Bh,-horizon. The magnesium and calcium supplies in the
soils are extremely low, while the aluminium content is high.
68
-------
Typical magnesium deficiency symptom of spruce. This yellow tip chlorosis of
spruce needles is only observed on extremely acidic soils. The dark green color
of recent needles is striking.
Severely damaged spruce at Ober-
warmensteinach also appear to be
more susceptible to potassium
leaching, which is two to three
times higher compared to the heal-
thy stands.
Hypotheses and
Research Approach
Our results up to now suggest that
magnesium deficiency might be the
primary stress factor inciting tip
chlorosis observed on spruce. It is
not clear, however, why this da-
mage has affected spruce in large
areas at high altitudes since 1980.
There is some evidence that this
decline is caused by atmospheric
pollutants (sulfur dioxide, nitrogen
oxides, and photooxidants). This is
because the region of northeastern
Bavaria is subject to relatively high
pollutant deposition rates (e.g. short
time sulfur dioxide maxima exceed
1400 ng per m3 of air). Besides di-
rect effects to foliage, for example
during frequent fog exposure, we
have to consider magnesium defi-
ciency in the soil which is probably
intensified by increased pollutant
impact. The relationship between
extreme weather conditions (e.g.,
drought or frost) and the develop-
ment of tip chlorosis in spruce has
not yet been defined. But we can
not exclude that increased nitrogen
inputs accelerate nutrient imbal-
ances. Recent laboratory experi-
ments proved that hydrogen ion in-
put to the forest canopy induces
significant acidification of the root
environment and leaching of mag-
nesium from the needles.
Based on these first results, the fol-
lowing unsolved problems are re-
ceiving top priority:
• What are the causes,for tip chlor-
osis accompanied by magne-
sium deficiency?
• Can the effects of individual or
synergistic stress factors be
quantified?
• What are the consequences of
cation leaching from the needles?
• Can tip chlorosis be mitigated by
magnesium-based fertilization
and what is the corresponding ef-
fect on soil and plants?
References
Zech, W. and Popp, E., Magnesium-
mangel, einer der Grunde fur das Fich-
ten- und Tannensterben in NO-Bayern.
Forstwiss. Centralblatt 102 (1983) 50-55.
Zech, W., Suttner, Th. and Kotschenreu-
ther, R,, Mineralstoffversorgung vermut-
lich immissionsgeschadigter Baume in
NO-Bayern. Kali-Briefe (Buntehof) 16
(1983)565-571.
Zech, W., Suttner, Th. and Popp, E., Ele-
mental analysis and physiological re-
sponses of forest trees in S02-polluted
areas in NE-Bavaria. Water, Air, and
Soil Polution 25(1985) 175-183.
Kuppers, M., Zech, W., Schulze, E.D.
and Beck, E., COj-assimilation, transpi-
ration and growth of Mg-deficient Pinus
sylvestris L., Forstwiss. Centralblatt
104(1985) 23-36.
Frevert, T. and Klemm, O., Wie andern
sich pH-Werte im Regen- und Nebel-
wasser beim Abtrocknen auf Pflanzen-
oberflachen? Arch. Met. Geoph. Biocl.,
Ser. B 34 (1984) 75-81.
Schrimpff, E., Klemm, O., Eiden, R.,
Frevert, T. and Hermann, R., Anwen-
dung eines Grunov-Nebelfangers zur
Bestimmung von Schadstoffgehalten in
Nebelniederschlagen. Staub - Reinhal-
tung der Luft 44(1984)72-75.
Hantschel, R., Kaupenjohann, M., Horn,
R. and Zech, W,, Water and element
transport in differently fertilized da-
maged forest ecosystems. Zeitschrift dt.
geol. Gesellschaft 136(1985) 473-480.
Kaupenjohann, M., Hantschel, R., Horn,
R. and Zech, W., Results of fertilisation
experiments with magnesium on prob-
able pollution damaged spruce (Picea
abies, Karst.)\n the Fichtelgebirge.
Forstwiss. Centralblatt 106 (1987) 78-84.
69
-------
iHHMHHHHHi
Bavarian Forest
K. Kreutzer
University of Munich
The Bavarian Forest together with
the Fichtelgebirge and Oberpfalzer
Wald forms the border mountains of
eastern Bavaria. This forest is di-
vided into two regions: the eastern
or Inner Bavarian Forest and west-
ern or Outer Bavarian Forest. The
Inner Bavarian Forest reaches ele-
vations up to 1450 m. The border
between the Federal Republic of
Germany and Czechoslovakia runs
along the ridges. There are frequent
plateaus between 1300 and 1100 m,
limited by a steep drop from 1100 to
800 m with many valleys forming
clefts. In contrast to this, the lower,
Outer Bavarian Forest, is rolling
countryside with wide valleys and
maximum altitudes of about 900 m.
On its south and west edges it
drops deeply to the Danube low-
land about 320 m above sea level.
Geologically, the Bavarian Forest is
a remnant of very old folded moun-
tains (Variscan folding) which were
elevated during the formation of the
Alps. They consist of granite and
gneisses in approximately equal
amounts. During the Ice Ages, the
region was subjected to solifluxion,
developing layered slope sedi-
ments, sometimes with boulder
fields. At the highest elevations,
there were local glaciers forming
moraines, Kar walls and small bas-
sins, now filled with water.
Local Climate
There are clear climatic distinctions
between zones of different eleva-
tion. While the mean annual temper-
ature is over 7°C, in the areas near
the Danube at the highest eleva-
tions it is about 3°C. Annual preci-
pitation also varies widely, between
800 mm in the low-lying areas and
1800 mm higher up, where there is
Spruce
65%
Others 3
Fir
Beech
Pine
Relative areas of tree species in the
Bavarian Forest. Norway spruce
dominates with a share of 65 %.
Percentage Damage Category
Spruce Fir
Pine Beech
Right:
Forest decline in the Bavarian Forest in 1986; percentages of damage catego-
ries within tree species. Two-thirds of Norway spruce show slight or moderate
damage; beech is slightly to moderately damaged on almost 80 % of the area.
Also more than 80% of silver fir are moderately or severely damaged.
70
CZECHOSLOVAKIA
¦ Pilsen
1457
1455
AUSTRIA
100 km
much snow, with depths reaching to
about 3 m. In summer, and espe-
cially in late winter, weather condi-
tions with high solar radiation occur
frequently, determined by continen-
tal Russian anticyclones. Particular-
ly on the slopes of the Inner Bavar-
ian Forest, such weather produces
a characteristic local climate with
cold air staying in the valleys, and
a warmer inversion zone on the
slopes. In the winter of 1984/85 the
temperature in the areas of cold air
accumulation dropped as low as
40° C.
Current Forestation
and Potential
Natural Vegetation
Of the current stand the main por-
tion is Norway spruce (65%) and
European beech (21 %). The poten-
tial natural woodland is still pre-
served over large areas. Corre-
sponding to the climatic zones, it is
also strongly stratified. The highest
peaks are naturally unwooded. As
elevation decreases, the next stra-
tum is the subalpine spruce forest
with mountain ash and occasional
patches of dwarf-pine. Below this,
the upper montane spruce-fir forest
succedes scattered with sycamore
and beech. In the following mon-
tane and submontane areas a
mixed forest type prevails, which
consists of varying proportions of
beech, spruce, fir and sycamore.
On slopes favored by temperature
inversion, beech is particularly vital
and competitive, while it is not
found in the cold zones of the val-
-------
Spruce, fir, and beech forest of different age classes at the foot of the Grosser Arber mountain in the Bavarian Forest.
leys. This also applies, to a lesser
extent, to fir.
There are small numbers of other
tree species such as ash and oak
which can even dominate depend-
ing on the site. On the lower levels
near the Danube there were origi-
nally beech-oak forests.
Past Land Use
In the Inner Bavarian Forest great
inroads were made by the glass in-
dustry as early as the 14th century,
but the composition of tree species
remained close to the natural mix-
ture. Only after 1910, increased utili-
zation and excessive herds of red
deer resulted in a decrease of fir,
which is aggravated today by the fir
decline. Even today, the Inner Ba-
varian Forest is practically unpopu-
lated.
In the Outer Bavarian Forest, human
settlements not only repressed the
forest, but changed it considerably
in some areas. One result was the
"birch mountains" and in recent
times, reforestation of agricultural
areas with spruce, which are no
longer economical. However, even
with such changes, many beautiful
uneven-aged, managed forests of
fir, spruce and beech remain.
Soil Types
The predominant soil types are
brown earths (Typic Eutrochrepts),
podzol-brown earths (Dystric Eu-
trochrepts) and, particularly in high
elevations, podzols (Typic Haplos-
thods and Haplohumods). Ground-
water influences many soils even on
slopes, forming gley soil types
(Haplaquepts)\u\\h transitions to
bog soils (Histic Humaquepts) and
peat, the latter mainly on flatter
parts of the slopes or in dips. The
soil formation of today is strongly
influenced by periglacial phenomena.
Forest Decline
According to the Forest Decline
Survey of 1986, two-thirds of the
Norway spruce in the Bavarian For-
est are slightly or moderately da-
maged. This pattern is similar to
Scots pine. As for silver fir, 61% are
already moderately damaged, and
21% are severely damaged or dead.
The second dominant species, Eu-
ropean beech, shows no decline
symptoms in one fifths of the stand,
45% reveal slight damage and one
third moderate damage.
71
-------
Research Site:
Luchsplatzl
Damage to
Norway Spruce
K.E. Rehfuess
University of Munich
Luchsplatzl
(Bavarian Forest)
Aspect:
gentle south-west slope
Elevation: 1200 m
Parent rock:
periglacial paragneiss sediments
Soil type:
podzolic brown earth (Ochrept)
Soil pH value: 4.1 - 4 6
Base saturation: 4-17%
Stand
Composition:
pure Norway spruce stand
Age: about 105 years
Planted or natural regeneration:
planted
Past land use: unknown
Known disturbances:
barren area before planting
(presumably resulting from
wind-throw)
Luchsplatzl is located on a gentle
south-west slope of the Grosser
Arber at an altitude of 1200 m. The
present stand of Norway spruce
was planted about 105 years ago on
a clear-cut area that presumably re-
sulted from wind-throw. The poten-
tial natural vegetation is a subalpine
Norway spruce forest, interspersed
with mountain ash and sycamore.
The soil type is podzolic brown
earth (Ochrept)derived from peri-
glacial paragneiss deposits. The
relatively high annual precipitation
lies between 1300 and 1400 mm.
Decline Symptoms
First symptoms of the decline were
recorded by the forest rangers in
1979 and 1980. Since then, there
have been signs of progressive
magnesium deficiencies. After tip
chlorosis of the needles, premature
shedding of older foliage started,
making the crowns increasingly
more transparent, especially in their
lower parts. Intensity of decline
symptoms has increased constantly
since 1980. The stand is now se-
verely damaged. The average nee-
dle loss is currently more than 60%.
Research Activities
Cause-effect investigations were in-
itiated at this site in the fall of 1981
by various teams of scientists from
the Faculty of Forest Science of the
(University of Munich, the Bavarian
Forest Research Institute (Bayeri-
sche Forstliche Versuchsanstalt)
and the Bavarian Environmental
Protection Agency (Bayerisches
Landesamt fur Umweltschutz). The
objectives of these research activi-
ties are as follows:
• quantification of the concentra-
tions of various airborne pollu-
tants
• precise description of the deve-
lopment of the disease and the
decline symptoms
• characterization of growth reac-
tions, changes in wood quality, in
root systems and in nutrient cy-
cles of affected and healthy trees
• prospects of strategies for im-
provement by silvicultural man-
agement and fertilization.
Results and Possible
Stress Factors
The decline symptoms described
are found on spruce in all age
classes (5 to 250 years). The affect-
ed trees always exhibit extreme
magnesium deficiency and low cal-
cium supply. They show a charac-
teristic yellow-golden chlorosis on
the upper side of the older needles,
being more pronounced on light-
exposed branches. Both diseased
and healthy trees have excellent ni-
trogen and phosphorus nutrition,
and their potassium supply is ade-
quate. Foliar chemical analyses
show normal levels of iron and man-
ganese, but relatively low concen-
trations of copper, zinc, lead and
cadmium. All of the trees have ex-
perienced a decrease in diameter
and volume growth over the past 10
to 15 years. The fine root biomass
of damaged trees has also de-
creased. There are striking tree-to-
tree variations in the development of
the decline symptoms. In fall 1983,
the stand suffered from an infesta-
tion of needle cast fungi (mainly
Lophodermium piceae and Rhizo-
sphaerakalkhoffii) and bark beetles.
The following natural stress factors
were identified: In spite of adequate
contents of total magnesium and
calcium in the soil, the amounts of
exchangeable Mg and Ca are rather
low. This nutrient deficiency is ag-
gravated as the soils are highly sat-
urated with aluminum, particularly in
the mineral horizons. The rooting
zone is restricted to the upper
60-80 cm of the solum due to the
occurrence of compacted subsoil
horizons. In places, the substratum
is very stony.
All these factors may inhibit uptake
of magnesium and calcium by the
roots. Additionally, the site is fre-
quently exposed to extreme weath-
er conditions with frost or acid fog
and cloud moisture. During high
pressure situations intensive irradi-
ation may cause strong photooxida-
tion of chlorophyll. Snow breakage
of the crowns is common in even-
aged stands of non-autochthonous
saplings.
Excluded Stress Factors
Average concentrations of atmos-
pheric sulphur dioxide and nitrogen
oxides at Xh\s s\le ate no\ suti\c\er%
72
-------
Damaged stand of Norway spruce with pronounced discoloration of the older
needles. The affected trees suffer from extreme magnesium defiency.
Monitoring Mean H+ SOjj"-S NOg-N NH/-N
site pH-Value kg per hectare
open land 4.50 0.4-0.6 20-30 5-12 7-15
spruce stand 4.15 0.6-1.3 40-52 13-16 9-15
Mean annual concentrations of hydrogen, sulfate, nitrate and ammonium ions in
precipitation and throughfall (spruce) at Bodenmais (9S0 m a.s.l.) from 1980 to
1983. The input of hydrogen ions, nitrogen and sulfur is noticeably higher in the
spruce stand than on open land.
Concentration SO2 03 NOx
per month M9 Per rn3
range
7-28
40-98
8-16
mean value
12
66
11.5
peak conc. (0.5 h)
52-340
71-182
13-37
Concentrations of airborne pollutants in the Bavarian Forest measured in 1983.
The mean values of sulfur dioxide (S03) and nitric oxides (NOx) are relatively
low, while In summer increased ozone (03) concentrations have been detected.
(Source: Bavarian Environmental Protection Agency),
high to cause severe disturbances
in the processes of photosynthesis
and transpiration. This conclusion
is supported by analyses of six-
month-old spruce needles which re-
vealed low sulphur content and by
the vigorous growth of lichens in the
opened crowns. It is assumed that
only peak concentrations of these
airborne pollutants would be of con-
cern in this area. Furthermore, there
is no evidence of toxic effects from
heavy metals being involved.
Hypotheses and
Research Approach
At higher elevations of the Bavarian
Forest, decline of Norway spruce
occurs on acidic soils derived from
granites, ortho-and paragneisses,
and shists. These soils are poor in
available magnesium and calcium.
A recently developed hypothesis
explains this disease as an inter-
action of photooxidants such as
ozone, acid deposition (mainly sul-
furic acid, nitric acid and their pre-
cursors), intensive solar irradiation
and frost shocks.
In summer or early fall, during epis-
odic atmospheric high pressure pe-
riods, high atmospheric ozone con-
centrations may damage foliar cuti-
cles and cell membranes, increa-
sing their ion permeability. During
subsequent periods, acid fog or
cloud deposition may accelerate
leaching, particularly that of magne-
sium, calcium, potassium and zinc,
from the already damaged needles.
This chain reaction explains the ex-
treme magnesium deficiency and
the insufficient calcium supply (in
some cases also the incipient potas
sium and zinc deficiencies) which
are reported to be an attribute of
this disease type. Moreover, the in-
adequate reserves of exchangeable
magnesium and calcium in the soil
as well as increased leaching of
both elements from the soil by the
impact of high atmospheric acid
deposition will contribute to these
nutritional imbalances.
Under these site conditions, the
trees cannot compensate for en-
hanced foliar leaching via root up-
take. In addition, the absorption
of magnesium and calcium is hin-
dered by antagonistic effects of sol-
uble aluminum in the soils. High at-
mospheric input of nitrogen may ag-
gravate the imbalances with regard
73
-------
Stand of old Norway spruce which has been infested by bark beetles after damage by extreme magnesium deficiency.
Year
Damage
N
P
K
Ca
Mg
Mn
Fe
Zn Al
Cu
100 needles
(needle loss)
- mg per gram dry wt. -
(ig per gram dry wt
mg
1981
healthy
15.9
1.9
5.8
1.7
0.69
181
45
20 78
4
470
diseased (80%)
17.0
1.7
4.4
1.2
0.51
158
37
13 71
5
560
1982
healthy
14.2
1.8
5.2
1.6
0.62
150
69
22 91
4
576
diseased (80%)
15.3
1.8
5.7
1.0
0.38
122
69
13 106
5
330
1983
healthy
15.9
2.0
5.4
1.5
0.70
191
48
20 100
9
441
diseased (80%)
15.0
1.6
5.6
0.9
0.29
110
41
11 80
3
374
The nutrient contents in K year old needles of the spruce stand at Luchspiatzi indicate that the diseased trees suffer from
extreme magnesium deficiency and are only poorly supplied with calcium compared to healthy neighbors. Both catego-
ries of trees, however, are well supplied with nitrogen and phosphorus. These nutritional Imbalances lead to metabolic
disturbances and possibly also to lower frost hardiness.
74
-------
Depth
Horizon
C0rg
N
P
C/N
C/P
K,
Ca,
Mg,
cm
- mg per gram —
- mg per gram -
9- 2
OF
505
20.9
1.5
24
339
1.2
0.6
0.3
2- 0
OH
468
20.3
1.6
23
285
1.8
0.9
0.4
0-10
Aeh
120
7.7
1.9
16
64
13.1
5.5
3.1
10-21
AhBv
62
3.6
1.3
17
47
15.4
5.6
3.5
21-41
Bv
42
1.9
1.0
22
43
16.0
6.8
3.5
41-68
II Bv
29
1.2
0.8
24
36
17.2
7.2
7.6
68-94
CVBV
12
0.5
0.8
24
14
19.2
8.5
9.1
Total soil nutrient contents. At the Luchsplatzl site the soil exhibits high levels of total nitrogen and phosphorous and
moderate amounts of weatherable potassium, calcium and magnesium. Considering elevation, the C/N and C/P ratios are
satisfactory.
Once a stand has been weakened
by these stresses, subsequent at-
tack of bark beetles or needle cast
fungi contributes to the final death
of the trees. There is growing evi-
dence that autochthonous stands
of Norway spruce suffer much less
than stands of unknown proven-
ance.
In combined climate and exposure
chambers, interdisciplinary experi-
ments are underway in order to test
this working hypothesis. Field trials
were laid out to test the effects of
calcium and magnesium-rich ferti-
lizers on the vitality of the affected
Norway spruce stands.
References
Bosch, Ch„ Ptannkuch, E„ Baum, U.
und Rehfuess, K.E., Uber die Erkran-
kung der Fichte (Picea abies Karst.)
in den Hochlagen des Bayerischen
Waldes, Forstwiss. Centralblatt 102
(1983) 167-181.
Rehfuess, K.E., Bosch, Ch. and Pfann-
kuch, E., Nutrient imbalances in coni-
ferous stands in Southern Germany.
Communicationes Instituti Forestalis
Fenniae 116(1983) 122-130.
Franz, F., Auswirkungen der Walder-
krankung auf Struktur und Wuchslei-
stung von Fichtenbestanden. Forstwiss.
Centralblatt 102 (1983) 186-200.
Depth
cm
Horizon
eff
EC
Ca2 +
Mg2+ K+ Na+ Al3+
10-3 mol ion equivalents per 100 g soil
H +
BS
%
9- 2
OF
276
1.72
0.92
1.73
0.26
17.8
4.4
17
2- 0
OH
467
1.16
0.66
0.64
0.11
40.4
2.1
6
0-10
Aeh
16.3
0.41
0.31
0.21
0.06
14.5
0.1
6
10-21
AhBv
104
0.28
0.11
0.08
0.01
9.7
-
5
21-41
Bv
8.7
0.24
0.09
0.10
0.06
7.8
0.1
6
41-68
II Bv
7.0
0.15
0.03
0.06
0.01
5.8
0.9
4
68-94
>
CQ
>
o
3.8
0.10
0.05
0.08
0.02
2.6
0.9
7
The cation exchange properties of the podzoiic brown earth (Ochrept). The forest soli at Luchsplatzl reveals that the
exchange complex is highly saturated with aluminium ions, but contains only a small amount of exchangeable calcium
and magnesium. Base saturation ranges from 4 to 17%. These conditions impede the sufficient uptake of magnesium and
calcium by the root system.
75
0-
1" 20-
o. 40-
0)
O
i6°-
80-
V
CaCI2 \
\\
Rooting Zone
\
I
3.5
i
4.0
pH-Value
4.5
Soil pH value at the research site
Luchsplatzl as a function of depth.
Soil pH is at the lower end of the
range in which hydrogen ions are pri-
marily buffered by exchangeable base
cations.
to magnesium and calcium (so-call-
ed dilution effect).
Inadequate magnesium supply will
prevent efficient synthesis of chloro-
phyll, which is a necessary prere-
quisite for maintaining healthy foli-
age, especially at high elevations
where intense photooxidation of
chorophyll occurs. Therefore, char-
acteristic deficiency symptoms de-
velop, namely tip-chlorosis of older
needles under conditions of high ir-
radiation. Magnesium deficiency will
generally depress physiological ac-
tivity of the needles and, in particu-
lar, frost hardiness of older needles.
As a result, frost shocks occurring
after warm periods in late winter or
early spring as in 1978/79, 1981,
1982 and 1983 activated the latent
disease in apparently healthy trees,
many of which are now faced with
dieback.
Norway spruce stands at higher ele-
vations are particularly endangered
by the following three conditions:
• long-term periods of high photo-
oxidant concentrations occuring
during high pressure situations
• large number of days with acid
fog or cloud moisture
• frequent frost shocks.
-------
Research Site:
Steinhuttel
Damage to
Silver Fir
K.E. Rehfuess
University of Munich
Steinhuttel
(Bavarian Forest)
Aspect:
gentle south-west facing slope
Elevation: 920 m
Parent rock:
periglacial paragneiss deposits
Soil types:
podzolic brown earth (Ochrept)
Soil pH value:
not determined
Base saturation:
not determined
Stand
Composition:
uneven-aged stand of
40% Norway spruce,
50% silver fir and
10% European beech
Age: all age classes
Natural regeneration or planted:
natural regeneration
Known disturbances:
careful management of largest trees
Steinhuttel is situated on a gentle
south-west slope of the Grosser
Arber at an altitude of 920 m. The
substratum is a podzolic brown
earth (Ochrept) derived from para-
gneiss deposits. The mean annual
temperature is 5.5-6.0°C, and the
mean annual precipitation 1300 mm.
The natural vegetation would be a
mixed spruce-fir-beech mountain
forest. The current stand is a mixed
uneven aged forest composed of
40% Norway spruce, 50% silver fir,
and 10% European beech.
Research Activities
The site serves exclusively as an
observational plot, where the devel-
opment of the decline syndrome is
monitored twice a year. No specific
investigations have been conducted
here, therefore there are no analyti-
cal data or experimental results.
This forest stand, however, is parti-
cularly well-suited for the demon-
stration of the typical decline symp-
toms of silver fir, which occur even
under the ideal conditions of an un-
even-aged forest. This is surprising,
because in such stands where trees
of all age classes are intermixed,
the dominant trees have developed
large, well-shaped crowns.
Results and
Possible Stress Factors
First symptoms of decline were re-
corded in 1976/77 after an extreme-
ly dry summer. Premature shedding
of older needles, mainly in the basal
and mid portions of the crowns led
to a progressive transparency. This
development is still continuing.
It is only the uppermost part of the
crown which remains unaffected,
dense and green. The so-called
stork's nest, which has always been
a typical feature of older firs, now is
formed much earlier than under nor-
mal conditions. Even middle-aged
trees may show this symptom. In
general, no foliar discoloration or
other nutrient deficiency symptoms
are observed.
The basal part of the stem as well
as the major roots often contain
pathological wetwood, strongly co-
lonized by bacteria. If this wetwood
extends into the sapwood, water
transport to the crown is inhibited.
Serious root damage is apparent,
with myccorrhizae frequently ab-
sent. Infestation by root pathogens
such as Armillaria mellea and Phy-
tophthora species and mycorrhizal
defects are common.
Dendrochronological studies indi-
cate that long-term growth decline
had already started in the late 1940s
or mid 1950s. The disease generally
affects only older trees (80 to 230
years), independent of the silvicul-
tural treatment. Younger stands, or
the regeneration in this uneven-
aged forest, show normal crown
density. There are no disturbances
to natural regeneration except in
cases of deer browsing.
Excluded Stress Factors
Nutrient deficiencies are not likely
the primary cause of fir decline,
although trees on poor soils are
probably more susceptible to injury
from other stresses. Forest mis-
management has to be excluded,
as the disease symptoms on old
silver firs are apparent in pure and
mixed stands, in even-aged and in
uneven-aged stands, in thin and
dense canopy forests. Foliar ana-
lyses at nearby sites revealed that
the impact of heavy metals, hy-
drochloric acid, hydrofluoric acid
and of sulphur dioxide is not signifi-
cant.
Conclusions
Typical silver fir decline phenomena
are observed on various types of
forest soils with different nutritional
status. There is obviously no corre-
lation between the occurrence of
the disease and the nutritional sta-
tus of the site.
The following common and inciting
stress factors have been identified,
based mainly on findings of den-
drochronological and pathological
investigations:
• drought as a cause of significant
reduction in fine root biomass
• bacterial infection of roots and
heart wood
• frost shocks causing premature
shedding of older needles.
In some locations - but not in gen-
eral - acid depositon or high peak
concentrations of sulfur dioxide may
act as contributing factors.
76
-------
References
Berchthold, R. et al., Standortskund-
liche Studien zum Tannensterben:
Kronen- und Stammerkmale von Pro-
bestammen aus funf bayerischen Be-
standen, European Journal of Forest
Pathology 11 (1981)233-243.
Berchthold, R. et al., Standortskund-
liche Studien zum Tannensterben:
Nadel- und bastanalytischer Vergleich
zwischen befallenen und gesunden
Baumen, Forstwiss. Centralbl. 100
(1931)236-253.
Reiter, H. et al.. Standortskundliche Stu-
dien zum Tannensterben: Ausbildung
und Mineralstoffgehalte der Wurzeln
von WeiBtannen (Abies alba Mill.) in
Abhangigkeit von Gesundheitszustand
und Boden, Allgem. Forst- und Jagd-
zeitung 154(1983)82-92.
The research site „Steinhuttel" Is covered by an uneven-aged spruce-fir-beech
forest. The mid-aged silver fir (left) has formed the so-called stork's nest; the
adjacent Norway spruce is also noticabiy damaged.
2.5
o
o> J? 3.0
O) to
2 O
5
-------
The Mun
Gravel
K. Kreutzer
University of Munich
Ingolstadt
\nn
¦/Munich
'Hohenkirchner
Forst |
Chiemsee
AUSTRIA
100 km
The landscape is formed by a pe-
neplain, almost 30 km wide and
slightly sloping to the north. Its ele-
vation is about 600 m in the south,
and about 440 m in the north. The
geology is dominated by fluviogla-
cial sediments of the last Ice Age
(Wurm), which deposited at the
head of the Inn and Isar-Loisach
glaciers mainly in the form of coarse
to medium, chalky gravel, with san-
dy intermediate layers. In the late
phase of sedimentation they were
frequently covered by thin fluvial
loam layers.
In the south, Wurm loess was depo-
sited on reliefs of moraines from the
penultimate Ice Age. The northern
part is now covered by bogs. The
peneplain is crossed by the Isar
river, which has cut its way through
Spruce
78%
Pine
Others
Beech Oak
Relative areas of tree species in the
Munich Gravel Plain. Norway spruce
dominates with a share of 78%.
the huge gravel deposits, forming a
series of late- and post-glacial ter-
races.
Local Climate
The average annual precipitation is
about 700 mm in the northern part,
and increases to 950 mm in south-
erly direction because of the in-
creased blocking effect of the Alps.
Large amounts of rain fall in the fre-
quent summer thunderstorms. The
mean annual temperature is about
7.5°C. Two climatological pheno-
mena should be mentioned: the
Fohn, a warm descending wind, es-
pecially in late winter and spring,
and late frosts, which can have a
very damaging effect on vegetation,
especially in May and the first half of
June.
Percentage Damage Category
*0
« 1
<2
<3
Spruce Deciduous
Pine
Current Forestation
and Potential
Natural Vegetation
The main part of the gravel plain has
been cleared and is used agricultur-
ally. Only in the south are major for-
est areas still to be found.
Original stands in the southern part
consisted mainly of European
beech and oak (Quercus peduncu-
lata), while in the northern part oak
and Scots pine were predominant.
The swampy ground supported al-
ders and, near the Isar, there were
subcontinental hardwood floodplain
forests. Few of these original woods
have remained. In the 18th and 19th
centuries the woods, damaged by
grazing and foraging, were trans-
formed into monocultures. Today
Norway spruce dominates in the
southern part and Scots pine in the
North. The swampy ground is main-
ly used as meadowland and for
corn. Broadleaf forests remained
only in the alluvial areas near the
Isar, but were strongly changed by
drainage, regulation of the water-
course and human use.
Past Land Use
The large forests south of Munich
played an important part in the de-
velopment of the culture and civili-
zation of the city. They provided raw
materials and energy, grazing and
forage for the agricultural population
around the city. In addition, they
served as hunting grounds for the
court in the days of electors and
kings.
Right:
Forest decline in the Munich Grave! Plain in 1986; percentages of damage
categories within tree species. The survey shows that 61 % of Norway spruce
suffer from slight to moderate damage; 40% of Scots pine are slightly and 13%
moderately damaged. One third of the deciduous trees shows decline.
100 -
%
80 -
60 -
40 -
20 -
0
78
-------
Typical woodland and grazing land in the Isar flood plains south of Munich. The original flood plain forests have been
radically changed as a result of water regulation and drainage.
Soil Types
Parabrown earths (Brown Earth-
Lessive, Osthic Luvisol)predomi-
nate on fluvioglacial sediments un-
der forest usage. Pararendzina soils
(Eutic and Lithic Hapludolls, Typic
and Lithic Udorthents) can be found
locally. On the loess clays of the
southern part more or less pseu-
dogleyed parabrown earths are
most important, often showing
signs of earlier cryoturbation.
The soils changed considerably
where they were used for agricul-
ture. Especially the parabrown
earths derived from gravel on the
plain were completely transformed
by years of plowing, fertilizing and
the influence of the city sludge. The
soils of the swampy areas, are also
seen to be transformed today by
drainage and the regulation of the
Isar.
The original Calcaric Fluvisols (Ty-
pic and Mollic Calcareous Udiflu-
vents) show an increasingly terres-
trial development, while the bog
soils are subjected to subsidence
on large areas as the result of min-
eralization.
Forest Decline
According to the Forest Decline Sur-
vey of 1986, on the Munich Gravel
Plain 40% of Norway spruce, the
dominant tree species, are slightly
damaged, and a further 21 % is
moderately damaged. Of Scots
pine, 40% are slightly and 13%
moderately damaged. About one
third of the deciduous trees shows
damage.
79
-------
wmKumuamm
Research Site:
Hdhenkirchner
Forst
Damage to
Norway Spruce
K. E. Rehfuess
University of Munich
Hdhenkirchner Forst
(Munich Gravel Plain)
Aspect: level
Elevation: 575 m
Parent material:
calcareous gravel of late
Pleistocene
Soil types:
weak podzolic parabrown earth
(Alfisol)
Soil pH value:
top organic layer: 3.8
mineral soil: 7.9
Base saturation:
40-100%
Stand
Composition:
94% Norway spruce,
6% Scots pine
Age: 100 years
Planted or natural regeneration:
planted
Past land use:
100 years under silvicultural
management
Known disturbances: none
The research site „H6henkirchner
Forst" is located in the Munich
Gravel Plain at an elevation of 575
meters. The soil is a weak podzolic
brown earth (alfisol) derived from
fluvioglacial calcareous gravel de-
posits dating back to the Pleisto-
cene period. Free carbonates exist
in the soil beginning at depths of
40 cm. The top layer of the mineral
soil has a pH value of 3.8, measured
in H20; the pH value at depths of 40
to 50 cm is 7.9. The mean annual
precipitation is approximately
1000 mm. The potential natural
vegetation is a mixed beech-oak
forest with some spruce. The pres-
ent stand, consisting of 94 % Nor-
way spruce and 6 % Scots pine, has
an age of about 100 years. The pro-
lific natural regeneration of Norway
spruce shows no damage. The
nutrient supply with nitrogen, phos-
phorus, calcium and magnesium
is excellent, but there is a slight po-
tassium deficiency in some trees.
Decline Symptoms
Damage to older Norway spruce
was first noted in 1980 or 1981,
starting with premature shedding of
older needles which led to thinning
of the crown. Foliar discoloration in-
duced by nutrient deficiencies was
not observed. Both the natural re-
generation in the understory of the
old stand as well as young trees in
neighboring stands remained vital.
Since about 1983, a recovery pro-
cess of many older trees started
with the formation of adventitious
shoots and continued at least until
fall 1986.
Research Activities
In spring of 1982, several research
teams from the Faculty of Forestry
of the University of Munich started
investigations at this site. The ob-
jectives are to develop a compre-
hensive description of the damage
symptoms under specific site con-
ditions, the growth reactions and
the impact of the disease on the
mechanical properties of spruce
wood from botanical, phytopatho-
logical, pedological and mensura-
tional perspectives.
Results and Possible
Stress Factors
The damage symptoms are notice-
able mainly on Norway spruce older
than 60 years. There are no signs of
long-term growth depression, but
there has been episodic reduction,
such as in 1976/77 and from 1980
to 1982. Continuous year-through
monitoring has turned up no evi-
dence of nutrient deficiencies. The
only exception is inadaequate
potassium supply. However, indi-
vidual or small groups of trees have
suffered severe heart root attack
caused by the root fungal patho-
gens Fomes annosus and Armi/laria
mellea.
A rapid reddening of older needles,
starting quite regularly in late Sep-
tember or early October, was ob-
served in 1982, 1983 and - only
slightly - in 1984. A high percentage
of those needles were infested by
Lophodermium piceae, L. macros-
porum, Rhizosphaerakalkhoffii and
other fungi. Premature needle cast
occured during winter, leading to
sudden crown transparency. Gen-
erally, four to five age classes of
younger needles remain unaffected
by these processes. Tree mortality
is very rare, as most of the trees
compensate for this needle loss by
forming adventitious shoots, nor-
mally on the upper side of the main
branches,
The following natural stress factors
were identified:
• water deficiency on shallow soils
with high gravel content and low
water-holding capacity, leading
to frequent water stress situa-
tions during periods of low preci-
pitation such as in 1976
• potassium deficiency due to the
poor supply of this element in the
soil
• frost shocks in 1978/79 and from
1981 to 1983
• infestation by root fungi (e.g.
ArmiHaria mellea) and occur-
rence of needle cast fungi at
least since fall 1982.
Foliar analyses also indicate a rela-
tively high level of chloride, sug-
gesting that the deposition of this
element may play a role in damage.
80
-------
Damage
Needle
N
P
K
Ca
Mg
Mn
Zn
Cu
Fe
degree
age class
mg per gram dry wt. —
|j.g per gram dry wt. -
healthy
1982
15.4
1.6
3.4
4.3
1.1
1430
23
3
49
1979
12.7
0.9
2.6
6.9
1.0
1983
10
4
54
diseased
1982
17.7
1.7
2.2
4.6
1.1
1548
22
3
53
1979
13.2
1.1
2.2
8.0
1.1
2263
9
1
63
Nutrient contents in Norway spruce needles of different age classes, analyzed in fall 1982, show uniformly good supply
with nitrogen, phosphorus, calcium, magnesium and trace elements. The potassium nutrition, however, is generally
inadequate and the diseased trees suffer more from potassium deficiency than the apparently healthy ones.
nates, the trees are adequately sup-
plied with these nutrients. There-
fore, soil acidification, as well as al-
uminum and manganese toxicity are
ruled out as stress factors. Damage
from photooxidation is virtually im-
possible in such low-elevation for-
ests. Foliar analyses indicate very
low levels of cadmium, lead, chrom-
ium, and nickel.
Hypotheses and
Research Approach
It is assumed that the extremely dry
summer 1976 initiated a first de-
crease in vitality and growth on this
shallow, gravelly substrate. The fine
root mortality caused by this desic-
cation might have raised the predis-
position of spruce for attack by root
fungi. Later on, frost shocks, as in
midwinter 1978/79 and in the late
winters of 1981, 1982 and 1983,
caused some immediate shedding
of spruce needles. They also ap-
pear to have increased the suscep-
tibility of older spruce needles' at-
tack by needle cast fungi. Subse-
quent attack of those fungi occured
for at least three years and resulted
in premature needle abscission and
thinning of the crowns, Soil induced
potassium deficiency on the one
hand, and exposure to wind and so-
lar radiation on the other may have
aggravated the damage. Since the
inciting stress was an episodic, cli-
matic event, the chances are good
Monitoring
pH-value
H+ SO|"-S
site
kg per hectare
open land
4.5-4,9
0.3-0.5 18-40
spruce stand
4.3-4.6
0.4 -0.7 32 - 47
Range of the annual means from 1980 through 1983 of the pH-value as well as
of the hydrogen ion and sulfate input in precipitation and throughfall measured
at Taubenberg located at a distance of 20 km from the research site. The data
show a low input of hydrogen and an increased sulfate deoosition.
pH Value
Measurements of pH of the slightly
podzolic parabrown earth (Alfisol) at
the Hdhenkirchner Forst reveal that
the upper-most horizon is moderately
acid, whereas the subsoil horizons
are rich in carbonates and exhibit
alkaline reaction.
Excluded Stress Factors
Direct impact of sulfur dioxide and
hydrogen fluoride on the foliage can
be excluded; the total sulfur con-
tents analyzed in the current foliage
are about 900 pg per gram of nee-
dles. Data from Taubenberg, locat-
ed at a distance of 20 km from the
site, show that damage is probably
no) caused by acid deposition on
foliage and soil. Since, at depths of
40 cm and more, the soil is rich in
calcium and magnesium carbo-
for recovery of the stand. The trees
are compensating for the foliage
losses by forming adventitious
shoots.
The further development of the da-
mage symptoms and the recovery
trends will be monitored during the
forthcoming years. Research is un-
derway to elucidate the biology of
the various needle fungi species in-
volved. There are discussions on an
experimental approach to test this
working hypothesis.
References
Kowalski, T. and Lang, K.J., Die Pilzflora
von Nadeln, Trieben und Asten unter-
schiedlich alter Fichten (Picea abies (L.)
Karst.) mit besonderer Berucksichti-
gung vom Fichtensterben betroffener
Altbaume, Forstwiss. Centralbl. 103
(1984) 349-360.
Rack, K. and Butin, H., Experimenteller
Nachweis nadelbewohnender Pilze bei
Koniferen. I. Fichte (Picea abies), Euro-
pean Journal of Forest Pathology 14
(1984)302-310.
Rehfuess, K.E. and Rodenkirchen, H.,
Uber die Nadelrote-Erkrankung der
Fichte (Picea abies Karst.) in Sud-
deutschland, Forstwiss. Centralbl. 103
(1984)248-262.
81
-------
Calcareous
K. Kreutzer
University of Munich
Ingolstadt
¦/Munich
Chiemsee
k Elendalm / _
AUSTRIA
100 km
Only the extreme southern part of
Bavaria borders the Alps at the
northwestern part of the eastern
Alps. It comprises a strip of the Cal-
careous Alps about 30 to 40 km
wide, running in a west-by-south-
west to east-by-northeast direction
on Bavarian and Austrian territory.
The Bavarian peaks reach heights
between 2300 m and just under
3000 m. To the North is the sub-
alpine „Flysch" zone with clayey
and sandy parent materials, and the
crystalline Central Alps are adjacent
to the South.
Tectonically the Bavarian Calcare-
ons Alps are part of the east alpine
orogeny, with a clearly north facing
imbricate and folded structure, origi-
nating from the Tertiary. The pre-
dominant rocks date from the Mid-
dle and Upper Triassic and the Ju-
rassic. One of the most important
Spruce
70%
Others
Fir
Beech
Relative areas of tree species in the
Bavarian Alps.
rocks in the Bavarian and Tyrolean
Alps is dolomite, which often forms
peaks. Because of its breccious
structure, it is also one of the most
significant sources of screes.
Local Climate
There is strong differentiation of cli-
matic zones by elevation, from the
warm climate of the valleys at 600
m, where fruit trees still flourish
(mean average temperature 6.5°C),
to the snow line at about 2000 m,
where there is no closed plant ca-
nopy (mean annual temperature
3°C). The timberline is mostly
between 1700 and 1900 m and
depends mainly on frost dryness.
Precipitation increases drastically
with height. In the valleys mean
precipitation is about 1300 mm
and near the summits it can be up
to 2500 mm.
Percentage Damage Category
-<0
< 1
<2
-<3 + 4
Spruce Beech
Fir Others
Current Forestation
and Potential
Natural Vegetation
The differentiation of climatic zones
by elevation determines the level of
the wooded belt of the Alps. On the
lower and middle slopes, mixed
montane forests predominate, with
Norway spruce, silver fir, European
beech and sycamore. Higher up
there are high-montane spruce-fir
forests and, above 1500 m, subal-
pine spruce forests. These give way
to dwarf-pine at about 1700 m. In
the eastern part of the Bavarian
Alps there is a zone of larches be-
tween 1700 and 1900 m, with some
spruce, and, especially at high le-
vel, Swiss stone pine (Pinus cem-
bra).
The gravelly parts of the valleys are
partly covered with mountain pine
and spruce, whereas in the valleys
affected by foehn, Scots pine form
autochthonous forests.
Past Land Use
Despite the often natural appear-
ance, the mountain forests have
been influenced by man to some
extent. Centuries ago, it was exten-
sively clear cut for mine timbers
and fire wood, especially near the
salt-works. The share of European
beech and silver firs was consider-
ably decreased. Alpine pasture and
deer browsing also decimated both
species. As a consequence, Nor-
way spruce is the dominant spe-
cies.
Soil Types
Because calcareous rocks are the
most important over large areas as
parent material for soil formation, a
Right:
Forest decline in 1986 in the Bavarian Alps; percentage of damage categories
within tree species. Most of the damage is moderate or severe. The deteriora-
tion of silver fir Is worst; only 9 % are not affected.
100-
%
80-|
60-
40-|
20-
82
-------
Norway spruce and larch In the Dachstein area of the Austrian Alps (60km southeast of Salzburg).
large number of rendzinas (Ren-
dolls) are to be found. They occur
on the scree slopes (talus fans) of
the mountain flanks as well as on
the massive carbonate rocks. How-
ever, on the talus fans there is a
clear tendency toward formation of
terra fusca soils (clays formed from
weathered limestone, typic fine tex-
tured Eutrochrepts). This is particu-
larly advanced on slope shoulders
and in dips, forming brown weather-
ing zones down to 60 cm depth.
These zones are also sometimes
differentiated by lessivation. The
rendzinas on solid limestone, how-
ever are often characterized by thick
and mostly very acid humus layers.
Apart from these soil types mainly
formed on limestones, parabrown
earths, brown earths and even pod-
zols developed on parent materials
free or poor of carbonates are com-
mon. A special soil type is the oxi-
gley which is formed on fine tex-
tured substrates of the slopes with
subsurface flow nearly the whole
year.
Forest Decline
According to the Forest Damage
Survey of 1986, more than half of the
Norway spruce, is moderately or
severely damaged; 81% of Silver fir
are damaged, also 86% of European
beech. Therefore, the forests of
this area are extremely endangered.
83
-------
Research Site:
Elendalm
Damage to
Norway spruce
K.E. Rehfuess
University of Munich
Elendalm (Bavarian Alps)
Aspect:
steep south-facing slope
Elevation: 1150 m
Parent material:
dolomite slope deposits
Soil types:
moder-rendzina (Ftendoll)
Soil pH value: 5.0-8.3 (CaCI2)
Base saturation: 80-100%
Stand
Composition:
100% Norway spruce
Age: 80-140 years
Planted or natural regeneration:
planted
Past land use: cattle grazing
The Elendalm investigation site is
situated on a steep south-facing
slope of the Schlierseer mountain
range, at an altitude of 1150 meters.
The soils are moder-rendzinas
(Rendolls)derived from dolomite
slope sediments. The thinned
spruce stands, aged from 80 to 140
years, were planted on former
cattle grazing lands. Scots pine and
heather (Erica carnea)comprised
the natural vegetation, which today
can only be found in some rare, in-
accessible regions.
Decline Symptoms
Norway spruce growing on these
south-facing slopes with shallow,
rocky alkaline-reacting soils have
always shown rather stunted growth
and symptoms of nutrient deficien-
cy. The older needles very often ex-
hibit tip chlorosis indicating inade-
quate supply of potassium. The yel-
lowing of the youngest shoots in the
lower parts of the crown is a typical
symptom of manganese deficiency.
A sudden decrease in vitality, pre-
mature shedding of older needles,
and even rapid death of individual
trees or smaller groups of trees was
observed in 1981. The symptoms
have progressed since then, leaving
parts of the stands seriously threat-
ened with dieback. Trees of all age
classes are affected.
Research Activities
Since fall of 1982, development of
this Norway spruce stand has been
monitored continuously, using soil
and foliar analyses as a first ap-
proach. The fungi flora of the nee-
dles of damaged Norway spruce
was examined by Professor Butin of
the German Federal Biological Insti-
tute for Agriculture and Forestry.
The Elendalm is an extreme exam-
ple of the widespread yellowing and
shedding of needles of Norway
spruce of all age classes on the
southern slopes in dolomite regions
of the northern Calcareous Alps.
Results and
Possible Stress Factors
The soil at the Elendalm site is a
rendzina (Rendoll) with a thick or-
ganic layer of the moder-type locat-
ed in a south-facing slope position.
The mineral soil horizons show high
pH values and are rich in humus,
calcium and magnesium, but quite
poor in potassium and phosphorus.
The alkaline reaction inhibits root
uptake of manganese, iron, boron,
and copper. Due to these site con-
ditions, potassium and manganese
deficiencies develop. In addition,
the supply of nitrogen, phosphorus
and iron is very poor.
The water holding capacity is very
restricted as a result of shallowness
of the substrate, high stone and
very low clay content. Therefore, pe-
riods of water deficiency stress are
common, especially on the upper
slopes and ridges, despite high
mean annual precipitation. Frost
shocks in 1978/79, 1981, 1982 and
1983, may have seriously damaged
the spruce stands already weak-
ened by potassium deficiency,
which is known to decrease the
frost hardiness. Severe infestations
by needle fungi, mainly Rhizophae-
ra, also occurred in 1982 and 1983.
The stands are partially afflicted with
root rot fungi (e.g. Armillaria mellea
and Fomes annosus).
Foliar analyses indicate that intense
radiation may enhance the photoox-
idation of chlorophyll in nutrient-de-
ficient needles. Ozone stress during
periods of intensive solar radiation
cannot be excluded. Under compar-
able conditions near Garmisch the
mean annual ozone concentration
in 1982 was in the range of 60 to 90
lag per m3. Other possible stresses
may be direct foliar exposure to ac-
id fog. Accelerated leaching of nu-
trients from needles may aggravate
soil induced deficiencies of pota-
ssium and manganese.
Excluded Stress Factors
In contrast to the diseased Norway
spruce stands at the higher eleva-
tions of the Bavarian Forest and
the Black Forest, the spruce at the
Elendalm are well-supplied with
magnesium and calcium. Detrimen-
tal effects of acid deposition on
the soil chemical status are impos-
sible, since the substrate is highly
buffered.
Direct effects of sulfur dioxide, ni-
trogen oxides, hydrochloric acid
and hydrofluoric acid on the foliage
can be excluded, as the mean an-
nual averages for sulfur dioxide
range from 8 to 10 and for nitrogen
oxides from 4 to 20 (ig per m3 air.
84
-------
At the research site Elendalm, dying Norway spruce grow on a shallow and rocky alkaline rendzina (RendoII) which is
derived from dolomite slope sediments. On the upper slopes, water deficiency stresses are common. Additionally,
the vitality of the stand is affected by the low potassium and manganese supplies of this substrate.
Degree of damage
Needle age
years
N
P K Ca
mg per gram DS
Mg
Mn
Fe
ng/g DS
Zn
healthy
20% needle loss
0.5
11.7
1.2
4.3
3.4
1.6
32
28
39
diseased
60% needle loss
0.5
11.4
1.2
3.0
2.8
1.8
20
29
27
healthy
20% needle loss
3.5
9.6
0.7
3.1
6.3
1.7
23
42
31
diseased
60% needle loss
3.5
8.6
0.7
1.7
4.7
2.0
16
34
17
Foliar nutrient levels of some healthy and some diseased Norway spruce at the Elendalm site. Affected trees suffer from
extreme potassium and manganese deficiency. The magnesium supply is excellent, since the soil is derived from dolo-
mite slope sediments. The nutrient status of the healthy and deteriorated spruce is insufficient for nitrogen and phospho-
rus. These nutrient deficiencies, together with water stress, weaken the trees such that they become more susceptible
to injuries by frost, atmospheric pollutants, as well as to root rot and needle cast fungi.
85|
-------
Depth
cm
Horizon
PH
(CaCI2)
Ocarb
Corg
C
mg per gram ground
N
P
C/N
C/P
7- 3
OF
5.0
3
487
490
14 2
0.56
34
863
3- 0
OH
6.4
15
330
345
16.6
1.01
20
328
0- 6
Ah
7.3
99
60
159
6.1
0.60
10
100
6-12
Af,Cu
7.5
114
22
136
2.5
0.33
9
68
12-60
Cv
8.2
138
-
138
0,7
0.08
-
-
Depth
cm
Horizon
K,
Ca,
Mg,
Mn,
Fe, Zn,
Cut
mg per gram
ng per gram
7- 3
OF
0.95
22
6.4
<200
1514
131
<20
3- 0
OH
2.60
56
18.6
290
10266
108
20
0- 6
\
1.65
165
62.9
<200
5020
< 50
20
6-12
AhCv
1.00
190
48.7
200
2980
50
20
12-60
Cv
0.70
213
71.1
200
1084
50
20
Soil reaction and total contents of carbonate and organic carbon and other nutrients in the rendzina soil at the E/endalm.
The substrate is covered by a weakly acidic organic layer. The mineral soil horizons (Ah and AhCJ are extremely shallow,
alkaline, and exhibit low nitrogen, phosphorus and potassium reserves, while the calcium and magnesium amounts are
very high. Such a site on south-facing slopes is not appropriate for a spruce stand. A Scots pine forest would be the nat-
ural vegetation.
The total sulfur content of half-year-
old needles was 812 ng per gram of
needle dry matter. There is no evi-
dence that toxic effects of heavy
metals are involved, since only
0.3 |ag lead and 0.02 ng cadmium
per gram needle dry matter were
detected in the current foliage.
0-
E
v
¦
o
\
£ 20-
\
Q-
0)
\
¦
_ 40-
o
V)
60-
I I 1 1
5 6 7 8
pH-Value
Measurements of pH in the soil at the
Elendalm site. The pH value rises in
the shallow sub-surface horizons from
weakly acidic to strongly alkaline.
Working Hypothesis
At the moment we are still in the
process of identifying the set of
stress factors. It is our impression,
however, that the reduction in tree
vitality due to unfavorable site con-
ditions, nutrient deficiencies and in-
adequate water supply play an im-
portant role as predisposing stres-
sors in the complex of disease
causes. Frost shocks, increased
photooxidation of chlorophyll, pho-
tooxidants and attacks of needle
cast fungi are assumed to contri-
bute as well.
The current situation of the spruce
stands at the research site Elend-
alm is alarming. Mixed reforestation
with pine and beech is hindered by
game browsing because of the in-
creased populations of chamois
and deer. Treeless and grass-
covered gaps develop in the stands
and on steep slopes snow-creep
occurs. This is destroying all regen-
eration and can also erode the soil
down to the parent rock. Therefore,
the entire forest ecosystem at the
Elendalm site is endangered.
Left:
Soil profile at the Elendalm site. The
rendzina soil (Rendoll) contains car-
bonate particles up to the surface of
the mineral substratum (Ah), but is
covered by a weakly acidic organic
layer of the moder type. The shallow-
ness of the soil, the high gravel and
stone content, and the rocky subsoil
are the causes for insufficient water
holding capacity.
86
-------
Branch of a damaged spruce tree at the Elendalm site. It shows a premature needle-loss; only the youngest needles
are green. On the older needles, symptoms of a weak potassium deficiency and severe infestation by needle cast fungi
are apparent.
87
-------
Black Forest
H.W. Zottl
University of Freiburg
100km
¦ Karlsruhe
FRANCE
'Freudenstadt
Kalbelescheuer
Basel
SWITZERLAND
¦ Zurich
The dark mountain ridges of the
Black Forest extend from Karlsruhe
to Basel, a distance of over 170 km.
The Upper Rhine Plain, a tectonic
trench, separates the Black Forest
from the Vosges on the other side
of the Rhine. These mountain
ranges are astonishingly similar:
Both ranges consist of an arched
crystalline pediment in the South
composed of gneisses and gran-
ites, gradually flattening out to the
North. The Black Forest and the
Vosges have about the same eleva-
tion. The Feldberg reaches 1493 m
and the Grand Ballon 1424 m, and
both are wooded to a large extent.
They also display the same contrast
with a steep drop to the Rhine on
one side and a gentler slope on the
Spruce
50%
8.5
Others'
Fir
12.5
Beech
Pine
Relative areas of tree species in the
Black Forest. Today Norway spruce
has a share of 50 %.
other. In the case of the Black For-
est this slope descends to the
Swabian heights of the upper Nek-
kar, and, in the case of the Vosges,
becomes the Lorraine Basin. To the
North and on the flat eastern edge
of the Black Forest the Buntsand-
stein-formation (a sandstone layer)
covers the crystalline base rock.
This forms a landscape of box
shaped ridges, which in the East
become an unbroken, more level
surface.
However, the Black Forest is a
mountain massif with a character of
its own, more impressive and with a
greater area (7860 km2) than the
Vosges (4600 km2). In the South it
attains a width of 60 km. It has no
Percentage Damage Category
100
%
80
60
40
20-
0-
Spruce Beech
Fir
unified North-South ridge line, and
no clearly delineated saddles re-
presenting horizontal connections
Local Climate
The Black Forest climate is charac-
terized as "atlantic": High precipita-
tion, little variation in temperature,
and long, snowy, but relatively mild
winters. Annual rainfall is generally
over 1000 mm. It increases with
altitude, and in parts reaches more
than 2000 mm.
Current Forestation
and Potential
Natural Vegetation
The woods in the southern part of
the Black Forest consist of a bal-
anced mix of Norway spruce, silver
fir and European beech, while
spruce dominates in the northern
part. Centuries ago, natural forests
of shade-loving beech and fir were
predominant in most parts of the
Black Forest. In places, sessile oak,
Scots pine, Noway spruce and
mountain pine formed the natural
vegetation.
Past Land Use
Exploitation in recent centuries has
repressed the natural vegetation of
the Black Forest. Grazing had a par-
ticularly severe and long-term influ-
ence on the forest, lasting from the
time of the major clear-cuts (10th—
14th centuries) up to the 20th centu-
ry. In addition, forest stands were
affected and changed by excessive
Right:
Forest decline in 1986 in the Black Forest; percentages of damage categories
within tree species. Over a third of Norway spruce, two-thirds of silver fir and
23 % of Scots pine show visible decline symptoms (damage categories 2-4).
Since 1983, European beech has shown increased loss of foliage.
-*0
-«1
+ 2
<3
88
-------
- •••
Kaltbrunner Valley In the Central Black Forest. 83 % of the valley Is wooded. Most of the forest Is privately owned. A loss
of these forests would deprive numerous local inhabitants of a living.
use of wood in mining ore, making
iron, glass, and charcoal, and in the
timber trade. This resulted in a de-
cline of the shade-loving European
beech and silver fir, mostly in favor
of Norway spruce.
Soil Types
The predominant soils in the Black
Forest are brown earths, podzols
and intermediate forms. Differences
in chemistry are mostly small on
the granite soils, but the distinctive
grain sizes of the stone are more
significant. The finer the granulate
of the parent rock, the more loamy
the product of weathering. Para-
gneisses mostly weather deeply to
fertile soils, while the orthogneisses
tend to form shallow, poorer soils.
Podzols frequently develop from the
sandy, low base sandstone. On
high lying ground, layers of poor
clay or geogenic clay layers often
result in water retention and hence
to the formation of pseudo-or stag-
nogleys.
Forest Damage
According to the 1986 Forest Da-
mage Survey made by the Federal
State of Baden-Wurttemberg, 74 %
of the wooded area shows decline.
The following picture emerges for
individual species:
Most of the silver fir shows damage
of category 2 (25 to 60 % needle
loss). About 12 % of the fir are
severely damaged or already dead.
Only about 14 % of the fir, indispen-
sible for local reasons, show no vis-
ible decline symptoms.
About a third of the Norway spruce
are healthy (needle loss 0—10 %),
a third is slightly damaged (needle
loss 10-25 %), and a third is mod-
erately damaged (needle loss
25-60 %). Since the beginning
of the 1980s, spruce has declined
much faster than fir.
Surprisingly, Scots pine are more
severely effected. 74 % of scots
pine show decline of grade 1
"slightly damaged", and of grade 2,
"moderately damaged". Only 23 %
of the European beech are healthy.
There are clear differences in the
degree of damage with age: Stands
over 60 years old are much more af-
fected than younger trees. In older
age classes the state of silver fir
and Norway spruce is particularly
worrying.
89
-------
Research Site:
Kalbelescheuer
(Southern
Black Forest)
Damage to
Norway Spruce
and Silver Fir
H.W. Zottl and E. Mies
University of Freiburg
Kalbelescheuer/St. Blasien
(Southern Black Forest)
Aspect: west-facing slopes
Elevation: Kalbelescheuer: 870 m
St. Blasien: 830 m
Parent material:
Kalbe/escheuer: granite
St. Blasien: granite and
gneiss moraine
Soil type:
podzolic brown earth (dystrochrept)
Soil pH value (CaCI2):
Kalbe/escheuer: 3.3 (5 cm)
4.0 (40 cm depth)
St. Blasien: 3.0 (5 cm)
4.6 (40 cm depth)
Base saturation:
Katbelescheuer: 6- 8%
St. Blasien: 15-25%
Stand
Composition:
silver fir, Norway spruce and
European beech
Age: 100-130 years
Planted or natural regeneration:
Kalbe/escheuer: planted
St. Blasien: natural
regeneration
Past land use: managed forest
Kalbelescheuer is located on the
western slope of the Southern
Black Forest at an elevation of
about 900 m. It is situated in the
Sulzburg valley, which is close to
the industrialized and densely pop-
ulated Rhine valley. The stand un-
der study is 100 to 130 years old,
comprising European beech (44 %),
Norway spruce (30 %), and silver fir
(26 %). Originally, fir made up al-
most half of this mixed forest, with
spruce and beech each accounting
for one fifth and several other spe-
cies for the rest of the natural vege-
tation.
The soil type at the site is an acidic
brown earth, which derived from
periglacial granite deposits. The soil
is deeply weathered, but with good
structure. The field capacity is only
moderate despite high precipitation
levels of 1600 mm per year.
Visible
Damage Symptoms
Silver fir
• Loss of foliage starting from the
inner to the outer part of the
crown, especially some meters
below the top
• sporadic appearance of tip
chlorosis
• increased development of adven-
titious shoots.
Heavily defoliated firs experience
dieback. A survey in fall of 1981
showed that damage to silver fir oc-
curs predominantly at elevations
between 800 and 1000 m. Increased
numbers of declining trees are situ-
ated on the west and south facing
slopes as well as on soils with a
low water-holding capacity and low
base saturation.
Norway Spruce
• Yellowing of needles, progress-
ing from the tip
• more pronounced on the upper
side of the needles or branches
• premature needle loss.
Damage appears first on older nee-
dles. The youngest needles are
usually green. Discoloration of the
previous year's needles begins at
bud break in late spring. Generally,
the diseased yellow needles remain
on the branches for three or four
years, so that defoliation is relatively
low. Generally, no growth reduction
of deteriorated spruce is observed.
Spruce dieback rarely occurs.
Research Activities
The Institute of Soil Science and
Forest Nutrition of the University of
Freiburg has monitored the concen-
trations of pollutants in precipitation
and throughfall over a period of two
years . This project was financed by
the German Research Foundation.
The Environmental Protection Agen-
cy of the State of Baden-Wurttem-
berg continuously monitors atmo-
spheric concentrations of sulfur dio-
xide, nitrogen monoxide, nitrogen
dioxide, and ozone.
The University of Hohenheim is ex-
perimenting with exposed bioindi-
cators to identify phytotoxic air-
borne pollutants at this site. Other
studies include tree growth dynam-
ics, and histological, histochemical,
and enzymological analyses of tis-
sue. The research is being done un-
der the auspices of the Federal Min-
istry of Research and Technology.
Results and Possible
Stress Factors
Comparative analyses of element
deposition were made at the Kalbe-
lescheuer and St. Blasien sites. The
Kalbelescheuer is located close to
the heavily industrialized and
densely populated Rhine Valley,
while St. Blasien, located some
30 kilometers east of Kalbelescheu-
er, has only little industry. The find-
ings for both sites show relatively
low deposition rates of sulfate
(SO4"). nitrate (NO5), and ammoni-
um (NH4+) ions, as well as of the
heavy metals, lead and cadmium.
However, the values for lead, sul-
fate, nitrate, and ammonium at
Kalbelescheuer are higher than at
St. Blasien.
The pH value of precipitation is be-
tween 3.4 and 5.6 (mean value 4.4)
at Kalbelescheuer, and between 3.6
and 6.5 (mean value 4.5) at St. Bla-
sien. The physical soil conditions at
Kalbelescheuer are good. The gran-
ular soil has a sandy-loam texture.
The available field capacity together
with the high precipitation level, is
sufficient for adequate water supply.
Soil chemical analyses show very
low base saturation (2-6 %) and on-
ly a small fraction of exchangeable
90
-------
Severely damaged, middle-aged silver fir In Munstertal at an elevation of 900 m. Its growth is very reduced, and the tree is
weakened by mistletoe. This tree will probably die in the next couple of years.
Research Precipi- H+ NH4-N Na+ K+ Mg2+ Ca2+ Zn2+ Cu2+ Pb2+ Cd2+ S04-S N03-N
site tation mg per m2 and year
Kalbelescheuer 1563 mm 81 960 390 290 90 535 23 5.1 12 0.25 1550 830
St. Blasien 1559 mm 56 670 310 210 74 390 14 3.8 7 0.18 1050 560
Open land precipitation and pollutant input (measuring period: September 1982 - September 1984) near the highly indus-
trialized Rhine Valley (Kalbelescheuer) and 30 km further east in St. Blasien, which is less Industrialized.
91
-------
magnesium and calcium. The pH
value of the upper soil layer is 3.3,
increasing to 4.0 with depth. Des-
pite the low pH in the top soil lay-
ers, the forest litter decomposes
well, so that almost no raw humus
layer is formed above the mineral
soil.
Foliar analyses in healthy and da-
maged stands indicate a good sup-
ply of nitrogen, phosphorus, and
potassium, but a relatively low level
of calcium and zink. Deficiency of
magnesium is present in both ap-
parently healthy and damaged
stands, but with significant differ-
ences between them. Soil analyses
of the upper rooting horizon show
that the declining stands have less
than half of the amount of ex-
changeable calcium and magne-
sium found in healthy ones.
The natural stress factors are mainly
wind and insufficient supply of cal-
cium and magnesium in the soil.
Stress caused by low precipitation
during the growing season in 1976
and 1983 may have damaged the
roots in the upper horizons. The
combination of airborne pollutants
(like sulfur dioxide and ozone) is
seen as an additional stress factor.
Causal relationships to forest de-
cline are probable.
Conclusions
Based on these results, it is specu-
lated that acid fog and ozone may
damage the foliage of trees causing
increased leaching of mobile ele-
ments like potassium, magnesium,
zinc, and manganese from the fol-
iage. Given adequate supplies of
these elements in the soil, the trees
are able to compensate for these
losses by higher uptake. Although,
the supply of potassium and man-
ganese is not problematic on the
granite derived soils at the Kalbele-
scheuer, incipient magnesium sup-
ply exists that inhibits the neces-
sary uptake. On potassium poor
soils, uptake of this element is like-
wise constrained. In all investigated
soils, deposition of acids from the
atmosphere may have additionally
reduced base saturation levels.
Application of fertilizers has led to
the mitigation of disease symptoms
after only one growing season.
Therefore, fertilization is a possible
tool to relieve any type of forest da-
mage related to nutrient deficien-
cies.
References
Mies, E. and Zottl, H. W., Zur Stand-
ortsabhangigkeit der Tannenerkrankung
im Sudschwarzwald. Allgemeine For-
stzeitschrift 37 (1982) 1296-1298.
Zottl, H. W. and Mies, E., Nahrelement-
versorgung und Schadstoffbelastung
von Fichtenokosystemen im Sud-
schwarzwald unter ImmissionseinfluB.
Mitteilungen der Deutschen Bodenkun-
dlichen Gesellschaft 38 1983)429-434.
Zottl, H. W and Huttl, R.F., Nutrient sup-
ply and forest decline in Southwest-
Germany. Water, Air and Soil Pollution
31 (1986)449-462.
Effective Cation Exchange Capacity [neq/g]
Effective cation exchange capacity in the soil at the Kaibeiescheuer. The mini-
mum amount of magnesium and the dominating saturation with aluminum are
clearly apparent.
Left:
Deeply weathered, rich brown earth developed from periglacial layers of granite.
The Ah-horizon is shallow, the litter is mineralized every year. The forest soil of
the Kaibeiescheuer has a dominant saturation of exchangeable aluminum ions
and a minimum amount of exchangeable magnesium.
92
-------
Research Site:
Freudenstadt
(Northern
Black Forest)
Damage to
Norway Spruce
H.W. Zottl and E. Aldinger
University of Freiburg
Freudenstadt
(Nothern Black Forest)
Aspect: level
Elevation: 830 m
Parent material: esozoic sand-
stone
Soil type: aquic dystrochrept
Soil pH value (CaCI2):
2.9 (3 cm); 4.2 (40 cm depth)
Base saturation:
3.7 % (in 0-40 cm depth)
Stand
Composition:
60 % silver fir, 40 % Norway spruce
Age: 70 years old
Planted or natural regeneration:
natural regeneration of fir,
spruce planted
Past land use:
old managed forest on former
pasture
Known disturbances:
insufficient thinning
In the Black Forest silver fir and Norway spruce show severe needle loss and
yellowing. By developing adventitious shoots the fir is able to compensate
partially for this loss of foliage. With spruce, such a compensation of needle
loss is very limited.
The forest stand is situated on a
plateau derived from mesozoic
sandstone and located between the
Kinzig and Murg river valleys in the
northern Black Forest at an eleva-
tion of 830 m. The forest soil is a
podzolic brown earth, with tempo-
rary stagnant water. The humus
type varies between mull-moder
and moder. The ground vegetation
is characteristic for the acid condi-
tions of this site: Vaccinium myrtil-
lus, Dicranum scoparium, Rhytidi-
adelphus loreus, Blechnum spicant,
Deschampsia flexuosa.
The natural vegetation, based on
pollen analyses, was a montane for-
est composed of silver fir and, to
a lesser extent, European beech,
which suffered damage starting
around the 12th century from log-
ging, resin use, cattle grazing, and
charcoal production. Gradually, the
forest has been transformed into a
spruce-rich stand that includes
some fir and only scattered beech.
The 70-year-old stand is the result
of natural regeneration (particularly
in the case of firs), and subsequent
reforestation.
93
-------
Monitoring Precipi- Mean H+ S042 N03 NH4+ N CI" Ca2+ K+ Mg2+ Mn2+
site tation pH value mol/ha kg per hectare
open land 1545 mm 4.5 531 29 28 7.3 12 25 2.7 2.8 0.9 0.09
spruce stand 1130 mm 4.1 1021 76 33 3.4 10 32 18.5 15.7 2.0 1.89
Bulk precipitation on open land and in thro ugh fall. Although the amount of through fall is smaller compared with the open
field precipitation, input of hydrogen ions to the spruce stand is higher because of the lower pH value. The filter effect
of the canopy and leaching from the foliage are revealed by the amount of sulfate and nitrate ions as well as of calcium,
potassium, and magnesium ions. The input of chlorine is remarkably high (after E vers).
Damage Category
Percentage
100-
*1
<2
-«3
1982 '83 83 '84
Fall Fall
Spring Spring
Development of needle loss for
Norway spruce from 1982 to 1984
(after Schroter).
Damage Symptoms
The first sign of damage to Norway
spruce was observed in 1981. Visi-
ble symptoms include yellowing of
the upper surface of older needles,
particularly in the upper crown. Yel-
lowing is followed by a loss of nee-
dles progressing from the lower
part of the crown toward the top
(sub-top-dying). The extent of de-
cline increased between 1982 and
1983, with the major change that
slightly damaged trees (11-20%
foliar loss) lost more foliage.
Besides deteriorated trees, the
stand also includes a number of
apparently healthy trees.
Research Activities
The University of Freiburg and the
Forest Research Station of Baden-
Wurttemberg are conducting nu-
merous research projects, with par-
ticular emphasis on soil and foliar
analyses. Fertilizer experiments are
Soil Chemical
Characteristics
0-
E
u
_ 20_
Q.
0)
^ 40-
o
w
60 H
? 9
v V20
o. ~
\
\
CaClA
1 I
\\
~ I
4
pH Value
0-
20-
40-
60-
Carbon Content [%]
0 20 40 60
1 I I I
• ¦
II
i I i
0 0.5 1.0 1.5
Nitrogen Content [%]
Soil properties of the research site Freudenstadt. Amounts of humus and
nitrogen decrease with soil depth. Although the poor soil is highly acidic, foliar
analyses show a sufficient nutritional status.
also underway in cooperation with
the BASF company.
Results
Needle loss and yellowing symp-
toms in Norway spruce are pro-
gressing, although there are rela-
tively low ambient concentrations of
pollutants.
Soil chemical analyses reveal high
acidity; the base saturation of only
3.7 % has reached a very low level.
The extremely small amount of ex-
changeable base cations in the soil
(e.g. potassium, calcium, and mag-
nesium) could lead to a poor nutri-
tional status of the trees.
Foliar analyses (first whorl) of appar-
ently healthy and damaged spruce
show only slight differences. The
low supply of calcium and particu-
larly magnesium is approaching de-
ficiency levels; supply of potassium
is still good.
The radial growth increment of da-
maged and healthy spruce does not
show a significant difference over
the past 40 years. Only since 1981
growth reduction occurred on de-
clining spruce, although this could
not be documented statistically.
However, compared with the growth
rates during the mid-1970s, the cur-
rent increment is still relatively high.
Conclusions
Although the soil is highly acidic
and poor in nutrients, the nutritional
status of the trees appears to be
sufficient in both the healthy and da-
maged spruce. Moreover, declining
spruce show no signs of a reduc-
tion in radial growth increment or to-
tal volume growth. The current data
do not allow clear insight into the
cause of the damage.
References
Please find the corresponding
references at the description of
the following research site.
94
-------
Research Site:
RoBberg
(Northern
Black Forest)
Damage to
Silver Fir
H.W. Zottl and E. Aldinger
University of Freiburg
Rossberg
(Nothern Black Forest)
Aspect: level
Elevation: 760 m
Parent material:
esozoic sandstone
Soil type:
aquic dystrochrept
Soil pH value (CaCI2):
3.7-3.9 on unlimed plots
4.0-4.7 on limed plots
Base saturation:
3.8 % (in 0-40 cm depth)
Stand
Composition:
40 % silver fir, 60 % Norway spruce
and scattered European beech
Age:
silver fir: 85-95 years
Norway spruce: 65-75 years
Planted or natural regeneration:
natural regeneration of fir,
interplanting of spruce
Past land use: managed forest
Both silver fir and Norway spruce show needie loss and yellowing of foliage. Fir
trees try to compensate for their foliage loss by developing adventitious shoots.
With Norway spruce this effect is less pronounced.
The research site RoGberg is locat-
ed near the Freudenstadt site, but
at a lower elevation (760 meters).
The forest soil is a podzolic brown
earth with temporary stagnant
water Stand and soil parameters
are similar to those of the Freuden-
stadt site. RoBberg has a slightly
warmer climate (annual mean tem-
perature of 7.5°C), and is subjected
to stronger westerly winds.
The first signs of silver fir decline
were detected at RoBberg in 1962.
The stands have been surveyed for
damage since 1974. Beginning in
1980, the Forest Research Station
of Baden-Wurtemberg has conduct-
ed spring and autumn surveys of
needle loss which, among other
things, showed a marked increase
until 1984.
Damage Symptoms
Decline of fir begins with premature
needle loss, starting in the lower
crown and progressing upwards.
The reduced terminal growth of
diseased firs has led to the forma-
tion of flattened stork's nests at the
crown top. The stork's nest is a typi-
cal feature of fir trees older than
100 years, but in declining firs it de-
velops much earlier. The growth
of adventitious shoots can be pro-
minent. Yellowing of the needles
occurs particularly on trees with
strong foliage loss.
Results and Possible
Stress Factors
The Universities of Tubingen and
Gottingen are analyzing the fine root
system dynamics and mycorrhizal
9rj
-------
Percentage
100 —
% -
80-
60-
40-
20-
Damage Category
1980 '81
Fall Spring Fall Spring Fall Spring Fall Spring
Development of needle loss for silver fir from autumn 1980 to spring 1984 moni-
tored at the Rot)berg site (after Schrdter).
relationships. The University of
Freiburg is investigating the effects
of liming.
Needle loss of silver firs increased
dramatically until spring of 1983.
Now it seems to be stabilized at a
low level, Measurements of ambient
sulfur dioxide concentrations yield
mean values of 20 pg per m3 and
peak values of 250 pg per m3. Soil
pH values are low. For this reason
some plots were treated in 1975
with lime containing magnesium
(3000 kg per hectare).
The base saturation at a soil depth
from 0 to 40 cm was 3,8 % before li-
ming, but has increased to 7.6 % on
the limed plots. The amounts of ex-
changeable calcium and magne-
sium increased while manganese
and hydrogen ions were reduced.
There are still high amounts of alu-
minum present in the limed soils.
In 1983, foliar analyses of the first
whorl of healthy firs indicated a
good supply of nitrogen, phospho-
rus and potassium. The effect of
liming is also evident here in the in-
creased contents of calcium ^and
magnesium and decrease in man-
ganese and aluminum levels of the
foliage.
Liming also affected the foliage of
damaged firs, although the nutrition-
al status differs only slightly from
that of apparently healthy trees. This
suggests that nutrient deficiencies
are not a cause for the fir decline
symptoms at this site.
Tree ring analyses show a marked
difference in annual radial growth
of healthy and damaged firs since
1962. No impact of liming was de-
tected on the dominant silver fir of
the stand studied. An increase
in growth of both healthy and da-
maged trees has been observed
since 1979.
Possible natural stress factors are
drought-induced weakening, strong
winds, and fungal infections.
Excluded Stress Factors
Based on the analytical data, sulfur
dioxide concentrations and nutri-
tional imbalances in the soil are not
considered primary causal agents
for the decline of fir at the RoBberg
site.
Conclusions
Liming resulted in higher pH values,
more favorable base saturation, and
increased foliar levels of calcium
and magnesium. No relationship
could be found between these ef-
fects and the degree of damage.
Calcium or magnesium deficiency
and low soil pH values together with
the low base saturation, are not
considered to be dominant stress
factors responsible for the decline.
Relative width of tree rings of healthy and damaged silver fir. Since 1960 the dis-
eased trees show reduction in growth compared with healthy trees. No reaction
in radial growth could be observed after treatment with time (3000 kg per hec-
tare). Since 1978 the annual increment of all firs increased.
healthy
75 100-
o
c
c
<
I I I I
1950 1960 1970 1980
Growth Period [year]
Liming
1946-1955 = 100%
damaged
96
-------
Damage
Liming
N
P
K
Ca
Mg
Mn
Al Zn
(needle loss)
mg per gram dry weight
ng per gram
healthy (15%)
control
13.2
2.31
9.80
8.00
1.77
3.10
485 66
healthy (13%)
3000 kg/ha
14.4
2.07
7.60
9.02
2.14
1.78
550 59
diseased (48%)
control
14.1
2.89
9.20
8.54
1.60
4.24
390 64
diseased (39%)
3000 kg/ha
13.8
2.42
7.22
8.90
2.17
2.29
335 66
Effect of liming on the contents of nutrients and aluminum in the foliage of healthy and damaged fir trees. On the limed
plots, the calcium and magnesium status increased while potassium decreased. For the healthy and damaged fir trees
there is no observed difference in their reaction to liming. Foliar analyses do not show nutrient deficiency.
References
Aldinger, E., Elementgehalte im Boden
und in Nadeln verschieden stark ge-
schadigter Fichten-Tannen-Bestande
auf Praxiskalkungsflachen im Buntsand-
stein-Schwarzwald. Freiburger Boden-
kundliche Abhandlungen 19(1987)
1-266.
Aldinger, E., Gesundheitszustand von
Nadelholzbestanden auf gediingten und
ungedungten Standorten im Buntsand-
stein-Schwarzwald. Allgemeine Forst-
zeitung 38 (1983) 794-796.
Evers, F.H., Orientierende Untersuchun-
gen langfristiger Bodenreaktionsande-
rungen in sudwestdeutschen Dungungs-
Versuchsflachen. Forsl- und Holzwirt
38(1983)317-320.
Evers, F.H., Ergebnisse ernahrungs-
kundlicher Erhebungen zurTannen-
erkrankung in Baden-Wurttemberg.
Forstwiss. Centralblalt 100(1981)
253-265.
Moosmayer, H.U., Schopfer, W., und
Konig, E., Ergebnisse der Waldscha-
denserhebung 1983 in Baden-Wurttem-
berg. Allgemeine Forstzeitung 39 (1984)
345-439.
Schroter, H., Entwicklung des Gesund-
heitszustandes von Tannen und Fichten
auf Beobachtungsflachen der FVA in
Baden-Wurttemberg. Allgemeine Forst-
und Jagdzeitung 154(1983)123-131.
Oberlander, W., Worth, R., Konig, E.,
Braunger, H., und Schroter, H., Ergeb-
nisse und Interpretation von zweijahri-
gen Schwefeldioxid-lmmissions-Mes-
sungen an Tannen-Beobachtungs-
flachen im Schwarzwald und in angren-
zenden Wuchsgebieten. Allgemeine
Forst- und Jagdzeitung 154 (1983)
175-180.
0-
E
o
® 20 -|
O
o
03
40-
0 M.
1 A
\\H!°
W
CaCl2\\
— Control plot
— Limed plot
I l
3 4
pH-Value
Effect of liming on the pH value of the
upper soil horizons.
Left:
Brown earth from mesozoic sand-
stone is loamy, but poor in nutrients.
Due to the acidic conditions the accu-
mulation of humus in the mineral soil
is limited. At greater depths the high
day content leads to temporary stag-
nant water.
97
-------
Northern Appa
F.G. Schroeder
University of Gottingen
Quebec mS
CANADA
Montreal
Toronto
¦ Boston
Buffalo
[New York
• Camels Hump
~ Whiteface Mountain
200 km
The Appalachians encompass a
strip of hills and mountains about
400-600 km wide in eastern North
America. These highlands stretch
from Alabama and Georgia in the
south about 2500 km northeast to
the maritime provinces of Canada.
The Appalachians were formed by
erosion from a montane range
which arose during the Paleozoic.
They correspond to the German
Mittelgebirge, which they also re-
semble in parent material and in
landscape. Low areas, hills and pla-
teaus alternate with high mountain
chains (up to about 2000 m), remi-
niscent of the Black Forest or the
Riesengebirge. Alpine forms are to-
tally lacking in the Appalachians.
During the Ice Age the northern part
was completely covered by the Nor-
dic ice sheet. Higher summits in the
south were ice-free, since they were
too low to acquire their own gla-
ciers. The southern boundary of the
ice, at about the latitude of New
York, is often assumed to represent
the border between the northern
and southern Appalachians.
The northern Appalachians mainly
consist of hilly and plateau land-
scapes. West of the Hudson-Cham-
plain Plain they are mostly between
500 and 800 m above sea level,
while to the east they are mainly
under 600 m. The higher mountain
ranges are the White Mountains in
New Hampshire (up to 1917 m),
the Green Mountains in Vermont
(1339 m) and the Adirondacks in the
northern part of New York State
(1629 m). In all these areas the ve-
getation varies with elevation. The
parent material is also different. Ac-
idic bed rock predominates in the
northern Appalachians, but, for ex-
ample in the Green Mountain, there
are also large limestone areas.
Local Climate
The climate in eastern North Ameri-
ca generally resembles Central Eu-
rope. However, there are also con-
siderable differences. Above all, the
temperature amplitude between
summer and winter is usually much
larger. Thus in eastern North Ameri-
ca no weather station can be found
which shows the same temperature
characteristics as a station in cen-
tral Europe. Where the summer is
as cool as in Central Europe, the
winter is extremely cold, and where
the winter is similar to that in central
Europe, the summers can be quite
hot. Since precipitation is also very
high (often over 1000 mm and with
the maximum in summer), the cli-
mate in eastern North American is
in general much more favorable for
woodland than in central Europe.
This is also a reason for the consid-
erably greater number of tree spe-
cies.
The range of temperatures is parti-
cularly large in the northern Appala-
chian region. At lower elevations the
average values in July are between
20°C and 22°C, in January between
- 5° C and -10° C with absolute
minima mostly far below - 30° C.
The low temperatures in the higher
mountain regions are more effective
in summer. The low winter tempera-
tures together with the high precipi-
tation result in snow cover lasting
several months, which only melts
temporarily when there is an inva-
sion of warm air in the most south-
ern areas.
Potential
Natural Vegetation
Regarding plant geography, most of
the northern Appalachians lie in the
boreo-nemoral transitional zone in
which the green summer deciduous
forests of the South are gradually
replaced by the evergreen boreal
conifer forests of the North. This re-
gion, corresponding somewhat to
southern Sweden and the Baltic in
Europe, is known in North America
as the Hemlock-White Pine-Nor-
thern Hardwoods Forest Region.
The natural vegetation of the sub-
montane areas is a mosaic of de-
ciduous trees and conifers. On av-
erage and better soils, neither too
wet nor too dry, the dominant tree
species are mostly sugar maple,
beech and yellow birch, along with
other deciduous species. Drier and
poorer sites are dominated by pine
and the damp or wet sites by hem-
locks.
In the mountains, the following
zones of vegetation are found, de-
pending on elevation:
Montane Transition Zone
On wet sites hemlock is replaced
by red and black spruce; similarly
red spruce replaces pine on the dri-
er and poorer sites. On better soils
red spruce is also found scattered
in deciduous woods together with
balsam fir.
Montane Zone
In the montane zone, even on the
better sites, all deciduous species
vanish except for yellow birch. In
their place are red spruce and bal-
sam fir. The latter dominates more
and more at higher elevations at the
expense of spruce. The highest
stands are pure fir which are finally
replaced by krummholz and give
way to alpine vegetation In the
Adirondacks the montane transition
zone begins at about 600 m, the
montane zone at 1000 m, the pure
98
-------
Camels Hump In the Green Mountains, Vermont. The foothills In the foreground are wooded with northern hardwoods.
fir forests at 1300 m and the alpine
zone at 1500 m. In the Green Moun-
tains, and especially in the White
Mountains, these boundaries are
usually about 100 to 300 m lower.
Past Land Use and
Current Forestation
In the lower-lying areas, especially
in New England, which was densely
populated very early, the original
forests have long been destroyed.
The current stands represent var-
ious stages of natural regeneration.
The same applies to most of the
White Mountains.
On the other hand, the original for-
ests are still preserved in some
higher regions of the Adirondacks
and the Green Mountains.
Forest Decline
Visible symptoms of damage to red
spruce at high elevations of the
North Appalachians have become
evident since the early 1980's. De-
clining stands show growth reduc-
tions which can be traced back to
the early 1960's. The most common
visible symptoms for high-elevation
red spruce have been loss of nee-
dles, premature senescence of
foliage and decreases in fine-root
biomass.
References
Braun, E.L., Deciduous Forests of East-
ern North America. Hafner, New York,
1950.
Fennemann, N.M., Physiography of
Eastern United States. McGraw Hill,
New York, 1938.
Knapp, R., Die Vegetation von Nord-
und Mittelamerika. Fischer, Stuttgart,
1965.
Kuchler, A.E., Potential Natural Vegeta-
tion of the Conterminous United State's.
Amer, Geogr. Society, New York, 1964.
Schroeder, F.G., Die thermischen Vege-
tationszonen der Erde. Ein Beitrag zur
Prazisierung der geobotanischen Ter-
minologie. Tuexenia 3 (1983) 31-46.
99
-------
Research Site:
Camels Hump
(Green Mountains)
Red Spruce
Decline
A.H.Johnson
University of Pennsylvania
Camels Hump
(Green Mountains)
Aspect: west facing slope
Elevation: 750-1150 m
Parent material: glacial till
Soil types:
Ochrepts - Spodosols - Folists
(low to high elevation)
Soil pH value:
3.3-5.3 depending on elevation
and horizon
Base saturation:
up to 30% depending on elevation
Stand
Composition:
below 780 m: northern hardwoods
780-900 m: transition zone
above 900 m: red spruce, balsam
fir and white birch
Age:
spruce up to 300 years old
Planted or natural:
probably natural regeneration
History:
below 780 m selective logging;
above 900 m little disturbed
Deposition rates
(estimated per hectar and year)
hydrogen ions: 2- 3 kg
nitrogen: 20 - 30 kg
sulfur: 20 - 50 kg
Camels Hump mountain is typical of
the main ridge of the Green Moun-
tains in Vermont. It is comprised of
schist overlain by glacial till which is
acidic, except where mixed with
some low lime till at low elevations.
Soils and vegetation are strongly
stratified by altitude. Lower slopes
(500-700 m) are characterized by
Spodosols and Inceptisols with
pH 3.5-4.5 in upper horizons, and
4.0-5.3 at depth. The forest vegeta-
tion is primarily northern hardwoods
(birch, beech and maple) with scat-
tered conifers, particularly red
spruce. The upper slopes are char-
acterized by shallow (0-2 m) acid
till and very acidic Spodosols or
Histosols (pH 3.0-4.5). The natural
forest consists of red spruce
(0-30%), balsam fir (20-80%), and
white birch (0-30%) which grades
into nearly pure fir above 1100 m.
Between the major forest types
there is a narrow transition zone
which has soils characteristic of the
upper, boreal zone.
The montane boreal forest is sub-
ject to prolonged contact with cloud
moisture (70-120 days) and con-
siderable water and chemical input
rather than older needles. Severe
frost damage (browning of newest
needles, in particular) has been
prominent during the last several
years, indicating one mechanism for
the foliar loss. There is only little
needle discoloration, except for oc-
casional necrotic spots on older
needles. Changes in foliage at the
cell level are present, including al-
terations of chloroplasts and tono-
plasts. Severe loss of growth (incre-
ment reductions at breast height) is
observed at Camels Hump, as it is
throughout the high elevations of
New England and the Adirondacks.
As far as we are able to determine
now, red spruce is the only species
which is showing excessive mortali-
ty, dieback, and increment loss.
From tree rings and written ac-
counts it appears that red spruce
dieback in Vermont and other
northeastern states began during
the mid to late 1960's. Quantitative
vegetation surveys indicate that be-
tween 1965 and 1979 red spruce
basal area declined approximately
40% in the class with breast height
diameters greater than 10 cm and
42-84% in the class with breast
40-
cs
-------
Deteriorating spruce-flr-whlte birch stand on Camels Hump. Spruce and fir show loss of foliage which typically occurs
first at the top and the extremities of lateral branches.
Research Activities
A variety of research has been con-
ducted on Camels Hump which has
resulted in a clear picture of the ex-
tent of the disease and the change
in the red spruce population. Nu-
trient and trace metal levels have
been determined in soils, deposi-
tion, and plant tissues and deposi-
tion rates of acidic substances were
measured at nearby sites. Long-
term (15-20 years) changes in the
heavy metal chemistry and soil or-
ganic matter content have been ob-
served and detailed lead cycling
studies have been conducted. Root
pathogens were also characterized
and quantified. Research at the Uni-
versity of Vermont, Yale University,
University of Pennsylvania and by
the U.S. Forest Service has contri-
buted to the characterization of the
spruce decline at this site.
Results and
Possible Stress Factors
Spruce mortality at Camels Hump is
likely a result of multiple stresses
which have acted in series or, per-
haps simultaneously. The initiation '
of the decline coincides with a peri- \
od of prolonged and severe droughts
in the Northeast and with a succes- <
sion of abnormally cold winters. A
predisposition to frost damage ap-
101
-------
The mortality in the high elevation spruce-fir forest on Camels Hump seems to
be progressing rapidly, only a few large individuals are left. The natural regener-
ation also decreased substantially.
100-
%
0)
o
c
«
¦e
o
Q.
E
(A
o
a>
a
cn
50-
Sugar Maple
Balsam Fir
Yellow
i Birch
\ A
\
Beech
/W^-
/ i
-^Red Spruce
White Birch
T
600
T
800 1000
Elevation [m]
1200
Distribution of overstory trees at Camels Hump as a function of elevation. The
species importance is the product of relative basal area and density.
pears to be a late stage of the dis-
ease. Secondary pathogens such
as shoe-string fungus (Armillaria
mellea) are involved, and recent
work additionally suggests the
presence of other root pathogens.
These natural agents probably play
a significant role, but their action
may well have been promoted by a
change in the chemical environment
caused by human activity.
Compared to low elevations, the
deposition of nitrogen, sulfur, hy-
drogen ions and of heavy metals,
(and probably other anthropogenic
substances) is 2-8 times greater
on Camels Hump. Total deposition
rates per hectare and year at mid to
high altitudes on Camels Hump
probably approach those observed
in the Soiling and at high elevations
in northeastern Bavaria (Hydrogen
ions: 2-3 kg; sulfur20-50kg;
nitrogen 25-40 kg). It is difficult to
exclude many stress factors be-
cause there has been little work car-
ried out to determine mechanisms
causing the decline.
Throughout New England, dieback
in spruce propagates with altitude.
Foliar and root aluminium levels de-
crease with elevation, whereas the
calcium to aluminum ratio in root
and foliar tissues increases. This
suggests that aluminum accumula-
tion by spruce is not a critical stress
¦ factor.
Stress from lead or other heavy me-
tals seems unlikely, as the lead
concentrations in soil solution
(< 5 ng per liter) and in forest soils
(< 1.5 nmoles per gram) are con-
siderably lower than levels reported
in the literature which are associat-
ed with altered biological activity.
Hypotheses and
Research Approach
I Observation of severe frost damage
to the newest needles in 1981 and
1984 suggest that winter damage is
a factor in the spruce decline on
Camels Hump. Reports of severe
frost damage to red spruce in the
New England mountains are abund-
ant as far back as about 1960. An
hypothesis currently being investi-
gated is that airborne pollutants
have reduced winter hardiness of
spruce. Initial studies include field
characterizations, and greenhouse
simulations accompanied by stud-
ies of the physiological processes
involved.
102
-------
800
Elevation [m]
Soil chemical
characteristics at
Camels Hump as a
function of elevation.
In the upper boreal
zone and in the
transition zone be-
tween the major
forest types the
pH-value and the
calcium supply are
considerably lower.
References
Siccama, T.G., Vegetation, soil and cli-
mate on the Green Mountains of Ver-
mont. Ecol. Mongr. 44 (1974) 325-349.
Johnson, A.H. and Siccama, T.G., Acid
deposition and forest decline. Environ.
Sci. Technology 17 (1983) 294a-305a.
Siccama, T.G., Bliss, M., Vogelmann,
H.W., Decline of red spruce in the
Green Mountains of Vermont. Bull. Tor-
rey Bot. Club 109(1982) 163-168.
Scherbatskoy, T., and Bliss, M., Occur-
rence of acidic rain and cloud water in
high elevation ecosystems in the Green
Mountains of Vermont. In: Proceedings
af the APCA Speciality Conference: The
Soil profiles at
Camels Hump. The
left profile shows
the fragiorthod soil
type at a height of
730 m. The upper
horizons are mixed
by windthrow.
The right soil pro-
file shows a toIIst.
These soils have
organic horizons
over 30 cm in depth
overlying the bed-
rock or as in this
case, glacial till.
Meteorology of Acidic Deposition. Hart-
ford, CT, 1983.
Friedland, A.J., Johnson, A.H., and Sic-
cama, T.G., Trace metal content of the
forest floor in the Green Mountains of
Vermont: Spatial and temporal patterns.
Water, Air, Soil, Pollution 21 (1984)
161-170.
Carey, A.C., Miller, E.A., Geballe, G.T.,
Wargo, P.M., Smith, W.H., and Siccama,
T.G., Armillaria mellea and decline of
red spruce. Plant Disease 68 (1984)
794-795.
Lovett, G.M., Reiners, W.R., and Olson,
R.K., Cloud droplet deposition in a sub-
alpine balsam fir forest: hydrological
and chemical inputs. Science 218 (1982)
1303-1304.
Friedland, A.J., Gregory, R.A., Karen-
lampi, L., and Johnson, A.H., Winter da-
mage to foliage as a factor in red spruce
decline. Canadian Journal Forest Re-
search 14(1984)963-965.
Burgess, R.L., David, M.B., Manion,
P.D., Mitchell, M.J., Mohen, V.A., Ray-
nal, D.J., Schaedle, M., and White, E.H.,
Effects of acidic deposition on forest
ecosystems in the Northeastern United
States: An evaluation of current evi-
dence. New York State College of
Environmental Science and Forestry,
Syracuse, NY, 1984.
Johnson, A.H., and McLaughlin, S.B.,
The nature and timing of red spruce de-
terioration in the northern Appalachians.
National Academy of Sciences Commit-
tee Report: Acidic Deposition, Long-
term Trends (1986) 200-300.
103
-------
Research Site:
Whiteface
Mountain
(Adirondacks)
Red Spruce
Decline
A.H.Johnson
University of Pennsylvania
Whiteface Mountain
(Adirondacks)
Aspect:
east and west slopes surveyed
Elevation: 700-1150 m surveyed
Soil type: Spodosol-Dysleptist
Soil pH value: 3.5-4.5
Base saturation: 1% and greater
Parent Material: glacial till
Stand
Composition:
below 800 m: hardwood with scat-
tered spruce
800-1200 m: red spruce-balsam
fir-white birch
1200-1400 m: Balsam fir
Age: spruce up to 300 years old
Planted or natural:
probably natural regeneration
History:
varies, heavy cutting in many areas
during late 1800's
Concentrations of pollutants
Ozone:
40-60 ppb (mean monthly values in
summer), peaks to 80-100 ppb
Sulfur dioxide:
greater than 5 ng/m3 in summer
(estimated average)
Whiteface Mountain is a peak in the
eastern portion of the Adirondacks.
It is comprised of Precambrian
gneisses overlain by glacial till.
Soils and vegetation are stratified
by elevation. This is representative
of the northern Appalachians, and
similar to Camels Hump, Soils
above 800 m are strongly acid Hu-
mods or Leptists having a very high
organic matter content. Climatic
conditions on Whiteface are similar
to those on Camels Hump. The
spruce-fir-white birch forest of the
upper slopes is subject to pro-
longed exposure to clouds and re-
ceives substantial deposition of
cloud water. Based on measure-
ments at the summit, ambient cloud
water pH is generally between 3.5
and 4.0. Ozone concentrations in
summer are between 40 and 60 ppb
with current daily maxima seldom
exceeding 100 ppb.
Results and
Possible Stress Factors
There are fewer data from Whiteface
than from Camels Hump. Foliar loss
patterns appear to be very similar to
those at Camels Hump, and after
snowmelt severe needle browning
has been observed. An abrupt
I growth reduction apparently began
in the early to mid-1960's, and per-
sists today. Considerable loss of
red spruce in the size class with
breast height diameter greater than
10 cm occurred between 1964 and
1982 in the high elevation stands,
with basal area in that zone decrea-
sing to about 30% of its earlier va-
lue. Of the remaining spruce above
900 m, approximately 50% showed
distinct signs of dieback in 1982
leaving only about 15% of the 1964
canopy spruce population as heal-
thy and vigorous individuals. Red
spruce in the size classes with
breast height diameter between 2
and 10 cm also declined between
1964 and 1982 by 16% in basal area
and 79% in growth, respectively. I
Presently, there is no reason to su-
spect that red spruce decline at
Whiteface is different from the dete-
rioration observed throughout the
northern Appalachians. Damage is
well advanced, but whether other
species are affected at Whiteface
and across the northern Appalachi-
ans is not known. Quantitative stud-
ies at Whiteface indicated that fir
and birch regeneration increased
from 1964 to 1982, but that basal
area of trees with breast height di-
ameters greater than 10 cm de-
clined. In the spruce-fir zone much
of the change in fir may be attribut-
able to blowdown or frost damage
which occurred as the stand open-
ed up due to spruce mortality. But
other stress factors cannot be ruled
out. Few data exist to give a quanti-
tative assessment of changes in fir
populations in stands over 1200 m,
but no significant departure from
normal stand dynamics are obvi-
ous. The fir population as a whole
does not show visible symptoms of
dieback or decline.
Research Activities
On Whiteface Mountain, research
on spruce decline is just beginning
through cooperative projects involv-
ing Oak Ridge National Laboratory,
University of Pennsylvania and the
Atmospheric Sciences Research
Center of the State University of
New York at Albany. Research on
atmospheric chemistry and, in parti-
cular, cloud chemistry, has been in
progress for many years. This pro-
ject, carried out by the Atmospheric
Sciences Research Center, now
provides data on cloud chemistry,
pollutant gases, precipitation chem-
istry, and weather conditions.
Hypotheses and
Research Approach
Forest dieback research is begin-
ning as an element cycling study,
with detailed measurements of
atmospheric deposition, nutrient
uptake, cycling, and loss from the
soils. Projects involving the physio-
logical response of trees to short-
term pollutant stresses have been
initiated.
.Several hypotheses are being test-
ed, One which we consider to be
important is that excessive nitrogen
deposition to the canopy causes
changes in nitrogen uptake and as-
similation which ultimately leads to
increased frost damage.
104
-------
Deteriorating red spruce and baisam fir on Whiteface Mountain. Presently, there is no indication that this decline is differ-
ent from damage observed throughout the northern Appalachians. It is still unknown whether other species are affected.
40-
8 20-
co
CO
0-1
1964-66
1982
Total Red Spruce Balsam Fir White Birch
Changes in the composition of the high elevation forests on Whiteface Mountain
over a 14-18 year period. A considerable loss of red spruce is observed since
the mid - 1960's.
References
Scott, J.T., Siccama, T.G., Johnson,
A.H., Breisch, A.R., Decline of red
spruce in the Adirondacks, New York.
Bull. Torrey. Bot. Club III (1984)438-444.
Burgess, R.L., David, M.B., Manion,
P.D., Mitchell, M.J., Mohen, V.A., Ray-
nal, D.J., Schaedle, M., and White, E.H.,
Effects of acidic deposition on forest
ecosystems in the Northeastern United
States: An evaluation of current evi-
dence. New York State College of
Environmental Science and Forestry,
Syracuse, NY, 1984.
Johnson, A.H., and McLaughlin, S.B.,
The nature and timing of red spruce de-
terioration in the northern Appalachians.
National Academy of Sciences Commit-
tee Report; Acidic Deposition, Long-
term Trends, p. 200-230(1986).
105
-------
Southern App
F.G. Schroeder
University of Gottingen
Pittsburgh
Philadelphia
Cincinnati
-Washington
Mt.^Mitchell
2024 m 2037-^
Ashville
Knoxville
¦ Atlanta
200 km i
The southern part of the Appalachi-
an system consists of four parallel
chains of differing width, named -
from northwest to southeast - Pla-
teau Province, Ridge and Valley
Province, Blue Ridge and Piedmont
Province. The greatest height is
reached in the southern section of
Blue Ridge Province. This part is al-
so designated as the southern Ap-
palachians in the narrower sense
and extends over 500 km in length
and 40 to 100 km in width from
southwestern Virginia to northern
Georgia. The southern Appalachi-
ans are mainly rolling hill and moun-
tain country from 700 to 1200 m
above sea level, surpassed in North
Carolina and on the Tennessee bor-
der by some higher ranges (Mount
Mitchell, 2037 m, the highest point
east of the Mississippi; the Great
Smoky Mountains, 2024 m). The
parent rock (mostly Cambrian to
Devonian) in the northern part and
on the eastern edge towards the
Piedmont is often very poor sand-
stone and quartzite. In the inner and
the western parts of the southern
Appalachians, on the other hand,
parent rock types containing a lot of
minerals, often gneiss, predomi-
nate. The quality of soil particularly
in this area is dependent on topo-
graphy: on ridges, peaks and over-
hangs the soils are poor and
leached out; on lower slopes and
coves they can also be very rich.
Local Climate
Summers in the low-lying areas
around the southern Appalachians
are damp and hot with average tem-
peratures in July around 26°C. Av-
erage temperatures in January are
between + 4 and + 7°C, though
severe frost down to - 20° C and
below occur everywhere. With in-
creasing elevation, the climate be-
comes more and more similar to
central Europe.
Average climate data do not show
the individual weather pattern. Pre-
cipitation in the Appalachians is
mainly in the form of heavy rain, al-
though the number of overcast days
in all seasons is much lower than in
central Europe. In summer there
can be several weeks of sunshine,
which leads to severe dryness in
low-lying areas, but is moderated in
the mountains because of the fre-
quent thunderstorms. The months
from November to February are
characterized by extreme tempera-
ture variations. The reason for this is
the regular change between tropical
currents of warm air from the Gulf of
Mexico and incursions of cold arctic
air from the northwest.
Potential Natural
Vegetation
The southern Appalachians are in
the climatically most favored part of
the American nemoral zone, in the
region of the central deciduous for-
ests, the "mixed mesophytic forest".
In the mountain woods of the south-
ern Appalachians various species
of rhododendron blossom early
in June. These shrubs, which grow
up to 5 m tall, are then covered with
a mass of bright to dark orange
blossoms.
Low Elevation
and Submontane Belt
The vegetation at low elevations
displays the greatest variety. Of
some 80 tree species that grow in
the Great Smoky Mountains Nation-
al Park (300 - 2024 m; area about
2020 km2), most are limited to the
planar-submontane zone. On better
soils, the tallest growing tree is yel-
low poplar (reaching 60 m), but al-
though important, it is never domi-
nant under natural conditions. On
drier and poorer soils, coverage by
the numerous species of oaks in-
creases. Conifers, mainly pines,
predominate only on the poorest
and driest sites.
This variegated submontane forest
extends in North Carolina up to
about 1000 m. This is the limit of
elevation for yellow poplar, pine,
hickory and many varieties of oak.
Above 1000 m one can distinguish
between several zones:
Montane Belt
On the richest soils, sugar maple,
ash, silver lime and horse chestnut
predominate. The latter two are re-
placed on average sites by red oak.
On the poorest sites sugar maple
and ash are replaced by more oaks,
red maple and several smaller
trees. There are practically no conif-
ers. Only hemlock is found on
damp and flat sites.
High Montane Transition Belt
This zone, above 1500 m in North
Carolina, is characterized by beech,
yellow birch and red spruce. As
in the montane transition zone of
the northern Appalachians, spruce
dominates the poorest southern
Appalachian soils. On better soils
beech and yellow birch are preva-
lent, with scattered spruce. Of the
trees of the montane zone, only the
horse chestnut is found here and in
considerable numbers on the best
soils.
Spruce-Fir Forest Belt
The high elevation conifer forest
zone begins in North Carolina at
about 1750 m and thus covers a
very small area on the few corre-
spondingly high mountains. It con-
sists of red spruce and Fraser fir,
106
-------
Damaged spruce and Fraser fir among blooming mountain ash in the foreground on Mount Mitchell, North Carolina.
which is found only in the southern
Appalachians. As in the northern
Appalachians, the share of fir
increases and that of spruce de-
creases with elevation.
Past Land Use and
Current Forestation
The first major human interventions
on the forests began with the settle-
ment of whites in the second half of
the 18 th century. In the mountains,
only a small area of less than 25%
was cleared. The remaining forests
were used for over 100 years by a
few self-sufficient settlers living off
woodcutting and livestock. At the
beginning of the current century,
when railways reached the moun-
tains, planned commercial exploita-
tion of the forest started, and then
. only the thickest and most valuable
trunks were taken.
After exploitation ended in the
1920s, many of the forests were left
to themselves. In the meantime
many wooded areas have had time
to recover, approaching natural
conditions. Even during the short
period of intensive human interven-
tion these forests have never been
far away from their natural condi-
tions. The only exception is the
chestnut. Formerly frequent, the
chestnut has been eradicated by
chestnut blight. This has been by far
the worst effect of an external influ-
ence on the southern Appalachian
forests.
Forest Decline
Damage is found on red spruce and
the balsam fir in the high elevation
areas of the southern Appalachians.
For high elevation red spruce a sub-
stantial growth reduction has been
observed, which started between
1958 and 1965. On the summit of
Mount Mitchell, older trees have
lost up to 75-90% of their foliage.
References
Schroeder, F.G., Waldvegetation und
Geholzflora in den Sudappalachen.
Mitteilungen der Deutschen Dendrolo-
gischen Gesellschaft67(1974) 128-163.
Stupka, A., Trees, Shrubs and Woody
Vines of Great Smoky Mountains Na-
tional Park, Univ. of Tennessee Press,
Knoxville 1964.
Whittaker, R.H., Vegetation of the Great
Smoky Mountains, Ecol Monogr. 26,
1956.
Additional references can be
found on page 99.
107
-------
Research Site:
Mount Mitchell
(Southern
Appalachians)
Decline of
Red Spruce
and Fraser Fir
R.J. Bruck
North Carolina State
University
Mount Mitchell
(North Carolina)
Aspect: all aspects
Elevation: 1600-2038 m surveyed
Parent Material:
Paleozoic granitic quartzite (1.5 billi-
on year old) and Sandstone
Soil types: Typic Hapla Umbrept
Soil pH value: 4.0 - 5.3
Base saturation: less than 10%
Stand
boreal montane forest of red spruce
and Fraser fir.
Composition:
continuous change from a low alti-
tude transition forest of 100% red
spruce to a high altitude ridge top
forest of 100% Fraser fir.
Age: all age classes
Planted or natural:
natural regeneration
Past land use:
below 1850 m: prior to 1910
lumber cut
above 1850 m: virgin
Known disturbances:
Attack of wooly adelgid during the
late 1950's. Serious mortality of Fra-
ser fir since the early 1970's.
Mount Mitchell, North Carolina, is
the highest peak in North America
east of the Mississippi River, rising
to an elevation of 2038 m above
mean sea level. Its main peak and
three high altitude ridges support
large populations of red spruce and
Fraser fir.
A survey was conducted from the
summit of Mt. Mitchell to below
1600 m during the fall of 1983 to
characterize and document any in-
cidence of decline or dieback in
the sprucefir ecosystem. Twenty
-two plots were established on the
mountain to account for fourteen dif-
ferent elevations, seven directional
aspects, and five slope class var-
iables. Forest floor surface litter,
organic and mineral soils were sam-
pled from soil pits excavated at
each site. All age classes of red
spruce and Fraser fir were assess-
ed for mortality and decline, and
dieback symptoms. From three
spruce and fir at each site, incre-
ment cores were removed for sub-
sequent analysis. Foliar, tissue and
fine roots were collected for chemi-
cal analysis and assessment of
ectomycorrhizal incidence on short
roots.
Results of the
Research Activities
Needle Loss
and Growth Reduction
Red spruce and Fraser fir growing
at altitudes above 1950 m were
found to be in a severe state of de-
cline. Trees at an age of 45 to 85
years show an average defoliation
of 75 to 90%, which was character-
ized by shedding of the oldest nee-
dles, often leaving a chlorotic tuft
of needles at the branch ends. All
trees at or above 1950 m elevation,
regardless of vigor, exhibited some
form of growth reduction beginning
in the early 1960's. On numerous
samples the twenty-one annual
growth increments from 1962 to
1983 were equivalent in total diame-
ter to the four annual increments of
1958 to 1961.
Precipitation data since 1930 show
that there was no drought in this re-
gion. In addition, cloud moisture
condensation on the branches and
needles of high altitude trees is
contributing substantial amounts of
water. Therefore growth reduction
cannot be attributed to a lack of
moisture.
Spruce stands below 1950 m on the
mountain appeared to be healthy
and vigorous. There is little, if any
evidence of defoliation, and thin an-
nual increments of growth were only
rarely observed.
Ectomycorrhizae
Recent studies at North Carolina
State University have demonstrated
that acidity of simulated rain influ-
ences the formation of ectomycor-
rhizae on loblolly pine seedlings.
Seedlings exposed to repeated
rains at pH-values of 4.0 or below
exhibited a deleterious effect to the
ectomycorrhizal roots. Roots treat-
2.0-
"e
_E
to 1.5-
o>
c
be
c
<
¦g
§
°~l ' T T I 1
1950 1960 1970 1980
Growth Period
[year]
Annual increment of red spruce
and Fraser fir on Mount Mitchell.
Since 1960 there is a steady growth
reduction.
ed with pH 4.0 rain simulations rap-
idly declined and the fungus mantle
became necrotic, eventually leading
to decline of the trees.
We observed at different elevations
on Mt. Mitchell a statistically signi-
ficant correlation between the per-
cent of mycorrhizal fine roots of
spruce and fir and the elevation at
which the trees were growing. Trees
above 1950 m averaged about 35%
mycorrhizal incidence while spruce
and fir at the 1600 m level exhibited
72% mycorrhizal incidence. High
altitude red spruce and Fraser fir
roots exhibited a far greater degree
of disintegration (fine root necrosis)
than did found at lower elevations.
Acid-rain simulation experiments in
greenhouses showed that rain simi-
lar to that falling in the Piedmont
and mountains of North Carolina
Fraser
Red /\
Spruce
108
-------
Severely damaged old Fraser fir and healthy regeneration on ridge top of Mount Mitchell (North Carolina).
100
%
75 H
s>
o>
CTJ
I so*
L-
0)
Q_
25-
0-J
Needle Loss
Mortality
of Trees
1600
1700
1800 1900
Elevation [m]
2000
2100
Needle loss and mortality of red spruce on Mount Mitchell as a function of alti-
tude. There is severe damage above 1950 m.
with a pH value of approximately
4.0, could have deleterious effects
on these laboratory-grown trees.
Mycorrhizal roots of red spruce and
Fraser fir at low and high elevations
on Mount Mitchell were similar in
appearance to the necrotic pine
roots in these rain simulation ex-
periments.
Heavy Metal Deposition
Lead concentrations in excess of
2.0 g per m2 were commonly ob-
served in the forest litter at eleva-
tions above 1800 m on Mt. Mitchell.
Samples from lower elevation (ap-
proximately 1500 to 1700 m) soils
showed considerably less lead
loading within the range of 0.1 to
0.2 g per m2. Forest litter samples
from west-facing slopes (predomi-
nant wind direction) consistently
109
-------
Fraser fir has been affected by the wooly adelgid since the end of the 1950's.
The burl at the branching has formed after attack of these sucking insects.
had higher lead contents. The con- Unusually large amounts of copper,
centration of lead in these high alti- nickel, zinc, and manganese were
tude soils and forest litter was equal also detected on Mt. Mitchell, all in
to or greater than that observed for amounts that far exceed those from
soils from mountains in the north- low elevation forests in North Caro-
eastern United States. lina. The possibility of lead and cop-
per toxicity to plants on Mt. Mitchell
must be investigated.
Hypotheses and
Research Approach
Observations suggest that major cli-
matic perturbation (i.e. drought or
abnormally high or low tempera-
tures) is not of significance in the
southern Appalachian Mountains.
This strengthens the hypothesis
that atmospheric deposition may
contribute to or be a cause of red
spruce and Fraser fir decline.
Some of the possible mechanisms
that need to be investigated:
• hydrogen ion deposition enhan-
cing the mobility of soil alumi-
num, resulting in toxicity to roots
and, hence, tree decline
• calcium and magnesium deple-
tion from the soil matrix resulting
in nutrient deficiencies
• death of ectomycorrhizal fine
roots from acid pulses initiated
by nitrogen deposition, which av-
erages from 22 to 40 kilograms
per hectare
• uptake of excess nitrogen result-
ing in abnormally succulent
crowns and shoots and decrea-
sing the resistance of red spruce
and Fraser fir to frost, wind desic-
cation, fungal pathogens, insect
parasites and air pollution
• effects of abnormally high con-
centrations of heavy metals in or-
ganic matter and mineral soil on
root vigor and hence damage to
red spruce and Fraser fir.
References
Bruck, R.I., Decline of montane boreal
ecosytems in Central Europe and the
southern Appalachian Mountains, 1984
Research and Development Confer-
ence, TAPPI, Technology Park/Atlanta.
Ga„ p. 159-163, 1984.
Bruck, R.J., Boreal montane ecosystem
decline in the southern Appalachian
Mountains: Potential role of anthropog-
enic pollution, Proceedings of the sym-
posium: Air polutants effects on forest
ecosystems, St. Paul, MN, The Acid
Rain Foundation (Publ.), p 137-155,
1985.
100-
(O
N
k_
o
o
>>
80-
60-
40-
20-
I 1 I 1 T
40 60 80
Needle Loss [%]
Correlation between needle loss and development of mycorrhizae of red spruce
on Mount Mitchell. When the mycorrhizae are fully developed there is only little
needle loss observed and vice versa.
110
-------
Side peak on Mount Mitchell.
All overstory trees are severely damaged or dead.
The natural regeneration, however, is healthy and vigorous.
-------
ORNL Studies on Forest Decline
S.B. McLaughlin
Oak Ridge National Laboratory
At the Oak Ridge National Laborato-
ry (ORNL) the impacts of airborne
pollutants on forest systems are be-
ing studied in a broad range of field
and laboratory studies conducted
within the Environmental Sciences
Division. Definition of unusual local
and regional forest growth trends
possibly related to atmospheric
pollutants, controlled studies to ex-
plore mechanism of action of spe-
cific pollutants, and management
of regional and national scale re-
search efforts are part of a multidis-
ciplinary research effort at the Oak
Ridge site.
Growth Reduction in the
Eastern United States
During the interval 1982-84 Oak
Ridge National Laboratory has been
coordinating a large regional-scale
project aimed at quantifying and in-
terpreting recent changes in forest
growth in the eastern United States.
The project was initiated in the
spring of 1982 in response to inten-
sified evidence of declining growth
of some northeastern tree species
and increased mortality of red
spruce at high elevations in New
England. Entitled "FORAST" (Forest
Responses to Anthropogenic
Stress), this collaborative project in-'
volving several eastern research
centers has implemented the col-
lection and analysis of approximate-//
ly 14,000 cores from 7,000 trees.
The principal objectives of this work
have been to determine the magni-
tude and timing of growth changes
and to find out the extent to which
these changes are correlated with a
variety of natural (climate, competi-
tion and soil fertility) and anthropo-
genic stresses (atmospheric pollut-
ants). Trees representing 34 spe-
Research Sites of the FORAST Project { \
• Research sites
r/MAINE1!
ft* VtT V /
( NY
y + \
* Mortality survey
/
* PENN /Sfe-
\ "1
OHIO /
•• V
. Jk/NJ
/MISSOURI (
^yw vav'h
/ VA
r • 7
/ARKANSAS/ ™ •
J -
NC »
w
* y-"7
Location of the FORAST sites, where increment cores have been collected.
Stars indicate where transects were established to estimate mortality.
cies have been sampled from more
than 100 forest stands in 15 eastern
states. Based on initial synthesis of
these data, the following preliminary
summary statements were made at
the time of this exchange:
• A systematic regional scale de-
crease in growth of red spruce
has occured within the study re-
gion during the past 20 years.
These changes have been found
in young and old trees at high
and low elevations and in the
presence and absence of
drought.
• In general, changes in growth
rate have been largest in areas'!
with highest pollutant loading
and have intensified during the
past 10 years.
Hardwoods have not shown ab-
rupt growth decreases of similar
magnitude although for all spe-
cies examined average growth
rates during the past 10 years
have been below average levels
years between 1930 and 1960.
No systematic response to cli-
mate across the region has been
noted and in more than 50% of
the species average growth in
the 1970's, a relatively wet peri-
od, has been below levels in the
dryer 1960's.
Site quality has had no consist-
ent effect on the magnitude of
changes noted to date.
Trace Metai Accumula-
tion in Forest Trees
Studies to determine levels of trace
metal accumulation in forest trees
have been undertaken at several
sites in East Tennessee. Results to
date indicate that concentrations of
several trace metals, notably iron,
aluminum and copper, have in-
creased in tree rings during recent
. decades. Localized higher levels of
other elements, most notably zinc,
were found in the vicinity of a large
coal-fired power plant in the area.
For iron, a period of increased accu-
mulation and decreased growth of
old short-leaf pine trees correspond
closely to emissions from open-pit
copper smelting carried out be-
tween 1855 and 1920 about 90 km
upwind at Copperhill.TN. Iron con-
centrations in tree rings returned
to preoperational levels following
implementation of sulfur dioxide
emission controls but have re-
112
-------
Short-leaf Pine, Cades Cove, GSMNP
Red Spruce, Mt. Kephart, GSMNP
oem
i m
1970
Xylem
1950
v \ ""*• V" '
.w \
Short-Leaf Pine, Cades Cove, Tennessee
1950
t
1900
Cores from red spruce and short-leaf pine growing in the Great Smoky Mountain National Park and in Tennessee.
A marked growth reduction can be seen since the end of the 1960s.
gained in close association with re-
gional increases in S02 emissions
during the past 30 years. At all sites
examined, the highest trace metal
concentrations were found in living
phloem plus cambium tissues. Con-
centrations of aluminum ranging
from 200 to 690 ppm, cadmium from
0.47 to 7.5 ppm, manganese from
150 to 450 ppm, and zinc from 27 to
120 ppm are reported to be at or
above the concentration range of
toxic effects to agricultural or herba-
ceous plants.
Hypotheses and
Research Approach
Physiological studies aimed at doc-
umenting the mechanisms respon-
sible for growth reductions are
urgently needed. These studies
should provide data on the sites
and processes involved in initial
dysfunction of physiological pro-
cesses on which growth depends.
They should emphasize disruption
of normal whole plant patterns of al-
location of carbon, water, and nu-
trient resources. Particular empha-
sis should be placed on quantifying
any altered balance of resource al-
location between roots and shoots
and on the differentiation of primary
versus secondary reactions. Addi-
tionally, changes in both gross
and net photosynthetic production
should be measured and changes
in the total amount and acitivity of
photosynthesizing surfaces should
be quantified.
Both the high inputs of nitrogen and
anomalous growth patterns ob-
served at many of the sites with for-
est decline suggest that nitrogen-
induced stresses may be involved
in many of these responses. The
physiology of nitrogen utilization
should be examined closely under
these conditions. Finally, the toxicity
of trace elements in tree tissues
should be determined in field and
laboratory experiments.
References
McLaughlin, S.B., Biasing, T.J., Mann,
L.K., and Duvick, D.N., Effects of acid
rain and gaseous pollutants on forest
productivity: A regional approach. Jour-,
nal Air Pollution Control Association
33(1983) 1042-1048.
Baes, C.F., and McLaughlin, SB., Trace
elements in tree rings: Evidence of re-
cent and historical air pollution. Science
224(1984) 494-497.
113
-------
Research Site:
Walker Branch
Watershed
(Tennessee)
Element Cycling
in Forest
Ecosystems
S.E. Lindberg
Oak Ridge National
Laboratory
Walker Branch (Tennessee)
Aspect: south slope
Elevation: 265-350 m
Parent rock: Dolomite
Soil type: Ultisols
Soil pH value: 3.8-6.0
Base saturation: 20-50%.
Stand
Composition:
mixed deciduous forest with oak-
hickory, yellow poplar, and pine as
dominants
Age: all age classes
Planted or natural:
natural regeneration
Past land use:
farm land and woodland pastures
Known disturbances:
fire in part of watershed in 1967
The role of the atmosphere in ele-
ment cycles in forests is being
quantified by an interdisciplinary
team of scientists at the Oak Ridge
National Laboratory (ORNL). The
research site is the Walker Branch
Watershed, a mixed deciduous for-
est at an elevation of about 300 m.
The area is typical of deciduous for-
ests in the ridge and valley province
of the southeastern United States.
Walker Branch has been instru-
mented with a unique array of auto-
matic wet and dry deposition sam-
plers above and below the canopy,
with soil moisture collectors on ma-
jor soil types and with several tow-
ers where pollutant concentrations
and meteorologic data are continu-
ously recorded.
Since 1975 several intensive stud-
ies have involved quantification of
deposition, canopy interactions,
and internal cycling of acid precur-
sors, trace metals, and nutrient ions
in representative oak stands.
Results
The data obtained indicate that the
atmospheric input dominates the
cycle of lead and has a significant
influence on the cycles of zinc and
cadmium in this oak forest. Deposi-
tion rates equal or exceed internal
cycling rates. Dry deposition contri-
butes some 10-50% of the total in-
put of these metals and cannot be
ignored.
Interactions between dry deposition
and acid precipitation result in con-
centrations of metal and hydrogen
ions on leaves which are consider-
ably higher than in rain alone. Direct
foliar absorption of lead may be the
primary pathway of its incorporation
in these trees.
In the oak forests dry deposition of
major ions is also significant, contri-
buting approximately 50% of the
input of sulfate and hydrogen ions,
and 60 to 70% of the input of nitrate,
calcium and potassium ions. Dry
deposition of sulfate, hydrogen and
nitrate ions is controlled by uptake
of sulfur dioxide and nitric acid va-
por. Particle input is important for
uptake of calcium and potassium
ions. Dry deposition dominates in
summer when the canopy is fully
developed. The determination of
element fluxes beneath the canopy
gives an indication of sinks of depo-
sited substances. During winter,
the bare crown has little influence
on deposition processes. During
the growing season, the canopy
leaches potassium and calcium
ions to incoming rain while absorb-
ing deposited nitrate, ammonium,
and hydrogen ions. The canopy ab-
sorbs about 50% of the free acidity
in rain, releasing undissociated
weak acids in the process. Acid ex-
change is species specific, and di-
rectly related to canopy leaf area
and residence time of moisture on
vegetation. These exchange pro-
cesses are accompanied by leach-
ing of foliar cation nutrients.
Hypotheses and
Research Approach
The influence of acid deposition on
foliar leaching has been estimated
from charge balance calculations'
and measurements of wet and dry
inputs including fluxes above and
below the canopy. It is assumed
that hydrogen ion input is the princi-
pal factor affecting foliar leaching,
and that hydrogen ion deposition in
unpolluted rain is negligible com-
pared to current average levels at
this site (mean pH-value 4.1).
Hence, the difference between total
amount of cations leached from the
canopy and the sum of all measu-
rable sources of anion leaching
(e.g. weak acids, sulfate ions, and
bases), including uptake of cations
(e.g. ammonium ions), represents
the enhancement of foliar leaching
due to acidic input. These analyses
suggest that about 40% of the cur-
rent cation leaching from the oak
canopy at Walker Branch can be at-
tributed to acidic deposition.
The soil studies suggest that sulfate
dominates the soil solution. It is
assumed that leaching of cation nu-
trients from the soil has been en-
hanced by acidic deposition and
that cycling of calcium, magnesium
and potassium ions have been ac-
celerated by acidic input. The soil
solution concentrations have in-
creased, leading to higher availabili-
ty to plants. Foliar leaching of these
nutrients is also increased. This hy-
pothesis remains to be tested; the
effects of increased cycling rates on
forest production are unknown.
Conclusions
The data support the hypothesis of
a major role of dry deposition in at-
114
-------
-V
Towers equipped with automatic samplers to measure rates of wet and dry deposition above and below canopy. Concen-
trations of atmospheric pollutants and meteorologic data can be recorded continuously.
mosphere/canopy interactions in
forests, and the assumption that in-
creased atmospheric inputs of ac-
ids and metals may be influencing
natural biogeochemical cycles in
this forest. It is estimated that depo-
sition supplies 40% of the nitrogen
and 100% of the sulfur demands for
growth of this forest. For the entire
forest, the sulfur requirement is ex-
ceeded by deposition, while nitrog-
en input contributes 5 to 10%. As
these proportions increase due to
industrial emissions, forests may
become increasingly dependent on
the atmosphere for nutritional re-
quirements, while simultaneously
being exposed to atmospheric pol-
lutants. Excess sulfur, nitrogen, and
metal deposition may already be af-
fecting high elevation forests in the
eastern United States and Europe.
References
Hoffmann, W.A., Lindberg, S.E., and
Turner, R.R., Precipitation acidity: The
role of the forest canopy in acid ex-
change. J. Envir. Qual. 9 (1980) 95.
Johnson, D.W., Richter, D.D., Lovett,
G.M., Lindberg, S.E., The effects of at-
mospheric deposition on K, Ca and Mg
cycling in two forests. Can. J. Forest
Res. 15(1985) 773-782.
Lindberg, S.E.,.Harriss, R.C., and
Turner, R.R., Atmospheric deposition of
metals to a forest canopy. Science 215
(1982)1609-1611.
Lindberg, S.E., and Lovett, G.M., Appli-
cation of surrogate surface and leaf
extraction methods to estimation of dry
deposition to plant canopies. In: Prup-
pacher, H.R., Semonin, R.G., and Slinn,
W.G.N. (Eds ), Precipitation Scaveng-
ing, Dry Deposition and Resuspension
Vol. 1, pp. 837-848, Elsevier Science
Publ., New York, 1983.
Lindberg, S.E., and Lovett, G.M., Field
measurements of particle dry deposi-
tion rates to foliage and inert surface in
a forest. Environ. Sci. Technol 19 (1985)
238-244
Lindberg, S.E., Lovett, G.M., Richter,
D.D., and Johnson, D.W., Atmospheric
deposition and canopy interaction of
major ions in a forest. Science 231
(1986) 141-145.
Lovett, G.M. and Lindberg, S.E., Dry
deposition and canopy exchange in a
mixed oak forest determined from ana-
lysis of throughfall. J. Appl. Ecol. 21
(1984) 1013-1028.
Lovett, G.M., Lindberg, S.E., Richter,
D.D., and Johnson, D.W., The effects of
acidic deposition on cation leaching
from a deciduous forest canopy. Can, J.
Forest Res. 15 (1985) 1055-1060.
Richter, D.D., Johnson, D.W., and Todd,
D.E., Atmospheric sulfur deposition,
neutralization, and ion leaching in de-
ciduous forest ecosystems. J. Env.
Qual. 12(1983)263-270.
115
-------
Comparison of Damage Symptoms
in Central Europe a
H E. Papke
Jiilich Nuclear Research Center
During the joint excursions of Ger-
man and American scientists in
1984, damage symptoms of various
tree species were discussed exten-
sively. Both similarities and differ-
ences in damage symptoms on Eu-
ropean and North American trees
were determined. The symptoms
found most frequently in the Federal
Republic of Germany and the Unit-
ed States of America, their regional
development and significant specif-
ic local features are summarized for
comparison in the following tables.
shoots with which the tree tries to
compensate for the loss of foliage.
In the northern Appalachians
the predominant form is loss of
youngest needles from the tips of
shoots. In.the southern Appalachi-
ans a frequently occurring form of
needle fall is also commonly ob-
served in German forests. Here
thinning progresses from the inner
to the outer portion of the crown.
There are transitional forms be-
tween these two types of damage
to foliage.
Differences and
Similiarities
Comparison of damage symptoms
is difficult. Forest ecosystems on
either side of the Atlantic are influ-
enced by considerable climatic
differences. Because of the Gulf
Stream, in Central Europe tempera-
tures are less variable than in com-
parable latitudes of the United
States. Correspondingly, in Ameri-
can forests, quite different combina-
tions of species are found together.
In addition, the excursions to affect-
ed areas showed that even on the
same site and for a single species
of tree the symptoms of damage
may differ quite considerably.
Nevertheless, a comparison of
symptoms leads to interesting and
sometimes surprising results. Des-
pite all the natural differences and
contrasts there is remarkable agree-
ment regarding symptomatology.
This includes particularly yellowing
(especially of conifers) and loss of
needles or leaves.
Loss of Needles
On both continents, as needle loss
increases, there is an unusually
strong formation of adventitious
Growth Reductions
Another point of similarity which
should be stressed is the radial
growth decrease, i.e. the reduction
in the amount of biomass formed
around trunk and branches. Incre-
ment cores from tree trunks, have
shown a considerable decrease in
diameter growth in some cases.
This feature of loss of vitality is to be
seen in all high elevation forests in
New England. Forest plantations in
low-lying parts of the eastern states
of the US are also affected. This
decline has occurred over a relative-
ly short period of time since the be-
ginning of the 1960s, as can be
seen from the smaller widths of the
annual rings.
In the Federal Republic of Germany,
similar reduction of growth is evi-
dent. However, the start cannot be
dated to within a few years as in the
United States. The development in
Central Europe has not followed a
uniform pattern. With spruce (Picea
abies), which has been examined
most closely, three different types of
reaction can be distinguished:
• Decline in the rate of growth dat-
ing from the mid to the late
1960s, long before crown da-
mage was evident. This pattern is
similar to that observed in the Un-
ited States and corresponds in
particular to growth of Appalachi-
an conifers.
• Greatly reduced diameter growth
starting 5-10 years later
(1970-75). There was a further
lapse of time here as well until
visible damage became evident
in the 1980s.
• A measurable narrowing of the
annual rings only began from the
mid to late 1970s. Visible damage
to the crown was evident at the
beginning of the 1980's. In indi-
vidual cases the decline in
growth coincided approximately
with the appearance of visible
symptoms.
Compensation
Mechanisms
On the other hand, spruce can
show normal growth even with nee-
dle loss over 50%. This suggests
that trees, as longliving organisms,
evidently possess some compen-
satory mechanisms. These make it
possible for them to survive even
severe damage. In the Federal Re-
public an increase of wood growth
has even been observed prior to the
appearance of visible symptoms.
On certain sites with little pollution
this may be attributable to nitrogen
input into the forest ecosystem,
which has continuously increased
since 1950, Thus, over a limited pe-
riod of time, both the negative and
the positive effects of deposited
pollutants can be compensated for
by the ecosystem's own resistance
to stress.
However, when the threshold of the
system or the site is reached or ex-
116
-------
The most frequent decline symptoms in Central Europe: the so-called "spruce window" (left), "stork's nest" crown of silver
fir (middle) and altered branching pattern of European beech (right).
ceeded, then damaging effects pre-
dominate. The tree, which until then
has been "normal", or growing well,
suddenly shows damage, which
can be aggravated especially by ex-
treme changes in climate.
Abnormal-Growth
Symptoms
In contrast to the United States, in
Central Europe there is a far greater
number of abnormal-growth symp-
toms. This reflects the fact that re-
search into causes began several
years earlier. For instance, abnor-
mal leaf formation (small leaves, or
"monster" beech leaves), abscis- .
sion of leaves and shoots while still
green, and change in growth pat-
tern ("stork's nest crown") have sel-
dom or never been observed in the
United States, if one discounts the
adventitious shoots previously men-
tioned
Most Important
Differences
Some of the most important differ-
ences in symptoms between North
America and Europe include:
• greater frequency of dieback from
the treetops in North America
than in Europe
• greater frequency of abnormal-
growth symptoms in Europe than
in North America
• substantial number of symptoms
observed in Europe are reported
rarely or not at all in North Ameri-
ca.
A major difference is the greater
prevalence in the United States of
the combination of marked growth
reduction without visible symptoms
of damage. In Europe there is usual-
ly a gradual decline of growth with
externally visible symptoms. Also,
there are no reports from the United
States to date of excessive seed
and cone production, which hap-
pened several years in a row in Ger-
man forests (particularly in 1982,
1983 and 1984). Similarly, in Ameri-
can forests there are no signs of de-
cline of the vegetation of the forest
floor.
Root Damage
Comparing research data on the
soil/root interface, the rhizosphere,
similar symptoms can be recog-
nized. There is serious root damage
in American and German forests.
This is evident in particular from the
decrease in the fine root biomass. j I
There are also parallels in the re-
search findings on disruption of
mycorrhiza (root fungi) formation,
which is vitally important for the
tree. These data indicate that there
probably have been major, and
possibly long-term, changes in the
soil.
117
-------
General
Observations
Federal Republic
of Germany
United States
of America
Occurence initially only damage at
higher elevations of the
mountain regions, later
also in low-lying areas
most severe damage at
high elevations
Species of at least four species of
tree affected conifer: Norway spruce,
silver fir, Scots pine,
Douglas fir
at least six species of
deciduous tree: beech,
oak, maple, ash, mountain
ash, birch
Type of forest symptoms of damage are
independent of the type of
forest
Age distribution
Pattern of
damage
at first old trees are affect-
ed, later trees of all ages
statistical distribution:
damaged trees standing
near healthy ones on the
same site
since 1985 there has been
a transition from sickness
of individual trees to area
damage, in particularly
hard-hit areas
(Black Forest, the Alps)
Type of soil on all types of soil, inde-
pendent of pH value and
nutrient status
more severe damage on
exposed sites facing the
weather side (southwest)
damage mostly on the
ridges of the Appalachi-
ans, independent of
exposure
at least two species of
conifer: red spruce, fir
(probably various
species of pine also)
regional growth reductions
in natural and cultivated
forests; visible symptoms
of damage only at high ele-
vations in natural forests
mostly old trees, but an
exception is the young
spruce on Mount Mitchell
more or less statistical
distribution with a marked
concentration at certain
elevations
predominantly on nutrient-
poor and acid soils
Distribution of forest damage in the Federal Republic of Germany and the east-
ern United States of America, after F. Cowling.
Yellowing
in high elevations on poor sites two-
year old and older spruce (above) and
fir (below) needles show yellowing,
which is caused by extreme magne-
sium deficiency. Mostly the youngest
needles are not visibly damaged.
Similar Symptoms in
Picea abies
Examination of Norway spruce (Pi-
cea abies), which has been planted
in many parts of North America,
showed, surprisingly, that some
had symptons almost identical to
stands in Central Europe. This fact
suggests that there is more similari-
ty between certain damage symp-
tons in the United Slates and those
observed in Central Europe than
had originally been supposed.
Affected Species
Altogether at least ten of the forty
European tree species are affect-
ed by "forest decline". A particular
characteristic of this is the nearly
synchronized appearance of simi-
lar damage symptoms over large
areas. Many have never been de-
scribed previously and, in the case
of many species, are evidently inde-
pendent of local site conditions.
Conservative estimates by Ameri-
can experts suggest that currently
two species of conifer (red spruce
and Fraserfir) are affected by "forest
decline". There is no significant evi-
dence concerning other species.
Surprisingly, in the eastern United
States only the forests of the Appa-
lachians have reached an acute
stage of damage. But these are nat-
ural, or nearly natural forests which
are taken to represent the most
stable stage of development of land
ecosystems. Evidently, even such
intact forest ecosystems cannot
compensate adequately in the long-
term for man-made disruptive influ-
ences. This suggests the intensity
of these damaging impacts and
how long their effects have accumu-
lated.
References
E. Cowling, Comparison of regional de-
clines of forest in Europe and North Am-
erica: The possible role of airborne
chemicals, pp 217-234. In: Proceedings
of the Symposium on Air Pollutants Ef-
fects on Forest Ecosystems, The Acid
Rain Foundation, St. Paul, MN (1985).
118
-------
Most Frequent Symptoms
Federal Republic
of Germany
United States of
America
Increased transparency of crown
by characteristic loss of foliage
loss of needles from the inner to the outer
portion of branches - the oldest needles
affected first
widespread in Norway spruce
and silver fir
only on Mount Mitchell with red
spruce
loss of the youngest needles or leaves
resulting in progressive thinning of the
crown from the top
frequent with deciduous trees
main type of damage in the
Appalachians
increasing transparency of the crown in
the area below the top through gradual loss
of foliage
observed in Norway spruce,
so-called „spruce window"
not observed
Yellowing of needles
Yellowing of older needles caused by lack
of magnesium and potassium; the young-
est needles are not visibly damaged
found in spruce and fir at high
elevations
in red spruce in New England
and the southern Appalachians
more severe yellowing of the upper side
of the needle than of the lower side,
because of greater exposure to light
prevalent in spruce and fir at
high elevations
individual cases observed in red
spruce in the Smoky Mountains
Loss of fine root biomass and
mycorrhizae
frequent in deciduous and
coniferous forests
similar findings
Diameter growth reduction
sudden growth reduction in the 1960s with
visible damage symptoms
widespread with spruce, fir and
Douglas fir
widespread with red spruce and
Fraser fir in the Appalachians at
high elevations
gradual growth reduction until tree dies
observed in spruce, fir and
beech
in some deciduous species
Frost damage to conifers
damage to needles, usually
several generations are affected
frequently only damage to
youngest needles
Abnormal growth
stunted growth and changes in size,
shape and color of needles or leaves
(small leaves or short needles)
in beech, oak, birch and spruce
common in shortleaf pine and
white pine, some maple and oak
altered growth pattern with increased
formation of short shoots
in beech
not observed
excessive formation of adventitious shoots
common in silver fir, Norway
spruce and larch
observed recently in high
altitude conifers and common in
deciduous trees
premature decline in growth of the main
shoots
"stork's nest" crown formation
in silver fir
not observed
excessive production of seeds and cones
common in spruce, fir, beech
and larch often observed sever-
al years in row
only with individual trees under
stress but mainly one year at a
time
Comparison of the most frequent symptoms of forest damage In the Federal Republic of Germany and the eastern United
States, based on the summary report of E. Cowling.
119
-------
Hypotheses
to Explain Forest Decline
E. Cowling, B. Krahl-Urban* and Chr. Schimansky*
North Carolina State University; *Julich Nuclear Research Center
At the present time at least five ma-
jor hypothetical mechanisms have
been proposed to explain the pos-
sible causes, development, and
progress of various types of recent
forest decline in Central Europe and
eastern North America. The hypo-
theses consider a number of po-
tential causal factors that affect for-
est vegetation, and reduce a com-
plex matrix of biotic and abiotic
stresses. These potential factors in-
clude dry and wet deposition of at-
mospheric pollutants to leaves and
needles, acidification of the soil,
ozone impact, microbial and fungal
infection, as well as incorrect Silvi-
cultural management of commercial
timber stands. No single factor has
been clearly identified as the cause
of the varied and widespread symp-
toms observed.
The hypotheses discussed below
are based on different assumptions.
The soil acidification hypothesis
emphasizes deposition of acidic or
acidifying substances from the at-
mosphere. This acidification, largely
induced by human activities, may
lead to release and leaching of nu-
trients and mobilization of toxic alu-
minum ions in soils. This may da-
mage roots, resulting in nutrient and
water deficiency in trees. The hypo-
thesis of complex high-elevation
disease includes a combination of
ozone injury, acid deposition, and
nutrient deficiencies that occur at
high elevation. Another hypothesis
involves predisposition of spruce
to needle cast fungi. The general
stress hypothesis postulates a
weakening of natural plant defense
mechanisms by air pollutants. The
potential effects of an over-abund-
ance of nitrogen have been deve-
loped into a further hypothesis. In
addition to these five hypotheses,
a sixth, effects of organic com-
pounds, was discussed during the
German-American scientific ex-
change.
These six hypotheses are present-
ed below. The order of the descrip-
tions in the text should not be con-
strued as indicating that one hypo-
thesis provides a more likely expla-
nation than any other. Each hypo-
thesis emphasizes specific obser-
vations, measurements, or theoreti-
cal considerations and portrayes
in some respect the theoretical
approach of some particular scien-
tists.
Hypothesis 1:
Soil-Acidification/
Aluminum- Toxicity
The soil-acidification/aluminum-tox-
icity hypothesis was developed by
Professor Bernhard Ulrich and his
colleagues at the University of Got-
tingen. In 1979, Professor Ulrich
predicted serious damage to forest
ecosystems in Central Europe,
even before widespread injury to
forests was actually observed.
The hypothesis of soil acidification
was developed mainly from long-
term studies which began in 1965
in the Soiling area near Gottingen.
This hypothesis states that the natu-
ral acidification of forest soils is in-
creased as a result of direct or indi-
rect effects of acidic and acidifying
substances from the atmosphere.
Natural acidification can be caused
by humus decomposition, nitrogen
transformations and higher relative
uptake of cations compared to an-
ions by plants. The pH value of the
soils is decreased by the continu-
ous deposition and release of acid-
ic and/or acidifying substances.
The rate of silicate and clay mineral
weathering is increased and alumi-
num ions are set free to the soil so-
lution.
Most research on the toxicity and
possible variation in the tolerance of
plants to aluminum ions has been
conducted with herbaceous vegeta-
tion. In such plants the following
physiological effects of aluminum
ions have been observed:
• reduction of uptake and transport
J of some cations (e.g. calcium,
magnesium, potassium)
^/% reduction in root respiration
• damage to fine feeder roots and
changes in root morphology
• reduction in elasticity of the cell
walls by interactions with pectins.
Research on germinating spruce
seedlings in nutrient solutions at
various aluminum concentrations
and pH levels has demonstrated
that low aluminum concentrations
stimulated development of lateral
roots, while larger amounts of alu-
minum induced a decrease in num-
ber and length of lateral roots. Mi-
croscopic examination revealed the
destruction of cell walls in the en-
dodermis of mature roots and dis-
ruption in development of the entire
central cylinder of undifferentiated
roots.
At low pH levels, aluminum ions de-
creased calcium uptake of roots
and calcium transport in stems of
120
-------
Soil-A cidification Hypothesis
Schematic representation of damage development on forest trees through combined action of acidic and acidifying sub-
stances from the atmosphere and climatic extremes. The resulting soil acidification is supposed to lead to leaching of nu-
trients and mobilization of toxic aluminum ions in soils.
Predisposing Stress Factors
Inciting Stress Factors
Ambient pollutants
(acids, heavy-metals,
organic compounds)
Loss of
needles and leaves
Airborne
pollutants
Damage to
needles and leaves
Nutrient leaching
from needles
and leaves
Soil
acidification
Nutrient leaching
from the soil
Toxic concentrations |
of metal-ions (Al3+)
Water anc
defici
(Mg, C
nutrient |
ency
* K) |
J
I
i
Disruption of
nutrient and
water uptake
I
Fine root
dieback
Frost
Climate
Drought
Water stress
Acidification
pulse (HN03)
spruce seedlings. Aluminum ions
apparently replace calcium and
magnesium ions at bonding sites of
the cell wall and form even stronger
complexes with protopectins. This
disrupts uptake of calcium and
magnesium, Also, plasticity of cell
walls and middle lamella is lost.
This is an important factor in quickly
growing tissues such as root-tip
meristems. These tissues are parti-
cularly sensitive to effects of alumi-
num ions.
Thus, increased soil acidification
and root damage serve as predi-
sposing stresses. They weaken
trees to the extent that so-called in-
citing factors become effective. In-
citing factors are responsible for the
visible symptoms of damage. They
include short-term high concentra-
tions of gaseous pollutants and ex-
treme climatic conditions.
In addition, the climate, acting as an
inciting stress, increases the effect
of acidic deposition. In warm years,
"acid pushes", caused by a higher
nitric acid production (nitrification),
can diminish the natural buffering
capacity of the soil. The peak levels
of acids in the soil lead to root da-
mage. Professor Ulrich and his col-
leagues have noted a relationship
between warm, dry years and sub-
sequent forest damage, thus provid-
ing a partial confirmation of their hy-
pothesis.
Research to date indicates damage
to stands from toxic aluminum ion
concentrations on specific sites.
This is especially true for declining
stands on acidic substrates at high-
er elevations. But soil acidification
cannot be the only cause of the new
type of forest decline, because
forest damage has also been ob-
, served on basic soils.
121
-------
Impact of ozone
Reduction in
nutrient uptake
from soil
Nutrient leaching from
needles by acidic mist/rain
.[^^uthen^deficienc^J
Photosensibility
X
Break-down of
chlorophyll
Decrease in assimilation
Damage to roots
I
Hypothesis 2: Complex
High-Elevation Disease
This second hypothesis combines
the theories of ozone damage of
Dr. Bernhard Prinz (State Institute
for Air Pollution Research, Essen)
with those of other scientists, such
as Professor Karl Rehfuess (Uni-
versity of Munich), and Professor
Heinz Zottl (University of Freiburg)
concerning the occurrence of mag-
nesium deficiencies in high-eleva-
tion spruce forests It describes the
combined effects of ozone, acid
deposition, and nutrient deficien-
cies at high elevations. High con-
centrations of ozone, as well as in-
sufficient nutrient supply (especially
magnesium) are believed to lead to
similar symptoms of damage to fol-
iage.
High ozone concentrations, occur-
ring mainly during periods of high
atmospheric pressure in summer
and early fall, cause damage to the
cell walls and the protective cuticu-
lar waxes of needles. The additional
stress of wet acidic deposition, pri-
marily of sulfuric and nitric acids, in-
creases nutrient leaching and pho-
tosensitivity which leads to partial
breakdown of chlorophyll. This in
turn causes decreased assimilation
which reduces root growth. Fewer
nutrients can be taken up from the
soil. This chain of events leads to
ever increasing damage over time
even under conditions of relative-
ly constant pollutant exposure.
Although pollutant concentrations
do not rise, damage to trees can
still increase rapidly.
Magnesium deficiency or ozone da-
mage causes yellowing of needle
tips, especially on older foliage, and
eventually leads to abscission (nee-
dle drop). Physiological activity is
decreased and sensitivity to frost in-
creases. It is speculated, that the
acute expression of latent injury
was caused by frost shocks occur-
ring in 1981, 1982, and 1983, possi-
ble leading to death of individual
trees. Support for this hypothesis is
provided by observations of tem-
poral and spatial relationships be-
tween degree of injury and ozone
concentrations, particularly on nu-
trient poor soils at high elevations;
increased leaching of nutrients from
foliage due to acid deposition; and
increased photosensitivity of foliar
tissues.
Magnesium deficiencies and ozone
exposure cannot be the only factors
responsible for recent widespread
forest decline. In certain locations,
however, ozone exposure com-
bined with acidic fog and rain, and
insufficient nutrient supply may lead
to increased leaching of nutrients
from foliage.
Hypothesis 3:
Red-Needle Disease
of Spruce
This hypothesis was developed by
Professor Karl Rehfuess of the Insti-
tute for Soil Science at the Univer-
sity of Munich to explain damage
symptoms on spruce in southern
Germany on sites with differing bed-
rock and different soil types at ele-
vations up to 700 m. This hypothe-
sis was a result of extensive field
observations, needle analyses, site
classifications, and of the study of
endophytic fungi, found mainly on
the older needles of mature trees.
In late fall of 1982,1983, and to a
more limited extent in 1984, "red-
dening" of needles was noted in
stands of spruce throughout south-
ern Germany. This was often ac-
companied by needle drop and
crown thinning. The older needles
turned a rust-red color and dropped
within a period of several weeks
prematurely so that the crown be-
came progressively more thin and
transparent from the inner to the ou-
ter and from the lower to the upper
parts. The occurrence of reddening
was concurrent with the develop-
ment of three types of foliar fungi:
Lophodermium picea, Lophoder-
mium macrosporum, and Rhizo-
sphaera kalkhoffii. These fungi are
secondary parasites which have
been previously noted to cause da-
mage on already weakened trees.
Infection of young spruce by both
species of Lophodermium has been
documented in the scientific litera-
ture.
Since reddening of foliage on older
spruce was found on almost all soil
types, independent of nutrient sta-
tus, the effects of nutrient supply
and other soil-mediated effects ap-
parently can be excluded. It is pos-
sible that elevated concentrations of
sulfur dioxide, nitrogen oxides, or
122
-------
Complex High-Elevation
Disease (left)
Schematic representation of damage
development on forest trees through
combined effects of ozone, acid depo-
sition, and nutrient deficiences at high
elevations. The typical damage symp-
tom is yellowing of older needles.
Excess Nitrogen Deposition
(right)
Schematic representation of damage
development on forest trees through
an over-abundance of nitrogen from
the atmosphere. Greater than normal
atmospheric deposition of biologically
available nitrogen compounds is as-
sumed to stimulate both forest growth
and the detrimental effect.
Excess nitrogen
supply from
the atmosphere
Fertilization effect
Soil acidification
Increased nutrient
uptake and
biomass production
~
Imbalance
of nutrient cycle
(P-, Mg- and K-deficiency)
f
Enhanced susceptibility
I
Toxic concentration of
aluminum-ions
~
Damage
to fine roots
*
Disturbance
1
of nutrient uptake
1
i
Damage to
needles and leaves
+
Loss of
needles and leaves
ozone predispose trees to infection.
Because this phenomenon has
been observed in forests far from
industrialized areas and in areas,
where smaller amounts of pollutants
have been documented, it is possi-
ble that predisposition is not always
necessary.
Professor Rehfuess has speculated
that the reddening of spruce nee-
dles also can be caused by clima-
tological factors, such as frost and
increased humidity in late winter or
early spring. These climatological
factors may also predispose the
trees to infection or favor the pa-
thogens in some way.
Recovery of trees, for example de-
velopment of adventitious shoots,
has been observed in many stands
where this symptom occurred. It
should be mentioned that in addi-
tion to the recent forest damage
which has been observed, cases of
damage have been noted from a
variety of fungi occurring naturally,
making the identification of a new
type of damage more difficult.
Presently, studies are being carried
out to determine whether, and to
what extent, particular fungi (e.g.
Lophodermium picea and Rhizo-
sphaera kalkhoffii) are involved in
this disease and if there is a correla-
tion between infection by fungi and
preceding pollutant injury to spruce.
Hypothesis 4:
General Stress
This hypothesis was developed by
a group of botanists, plant patholo-
gists, and physiologists led by Pro-
fessor Peter Schutt at the University
of Munich. It is based on field and
laboratory studies of damage on
various tree species, but especially
spruce and beech. The studies in-
clude observations of altered gas
exchange reactions and increased
production of growth hormones be-
fore and during damage. According
to this hypothesis, deposition of
atmospheric pollutants, including
growth-altering or toxic substances,
reduces photosynthetic activity and
the formation of important secon-
dary metabolites.
It is believed that even low concen-
trations of pollutants are sufficient to
cause some of these reactions. The
initial damage can lead finally to re-
duced assimilate supply to the root
system and an accumulation of tox-
ic substances in the shoots. This re-
sults in poor development of the
fine root system and decreased vi-
tality of mycorrhizae. The develop-
ment of the mycorrhizae may be
stopped completely. Water and nu-
trient uptake is diminished and the
crown no longer receives sufficient
supplies. The result is premature
senescence of needles and leaves.
This hypothesis encompasses
many different symptoms of forest
decline. For the same reason, how-
ever, it will be difficult to test experi-
mentally.
Hypothesis 5:
Excess Nitrogen
Deposition
This hypothesis was first proposed
by the Swedish soil scientist, Carl
Olaf Tamm, and later reinforced by
Bengt Nihlgard. They suggest that
greater than normal atmospheric
deposition of biologically available
123
-------
nitrogen compounds, principally ni-
trate and ammonium ions as well as
nitrate and ammonia vapors, could
be injurious to forests. This hypo-
thesis is based on a series of isolat-
ed experiments and certain theoreti-
cal considerations that are outlined
below.
Forest trees have always obtained
an important part of the nutrients es-
sential for growth from the atmos-
phere. Airborne nutrients are taken
up directly through foliage as well
as through roots. Forest ecosys-
tems evolved in preindustrial times
when the amounts of nutrients in
the atmosphere were very low. As
the industrial revolution gathered
momentum during this century,
however, great amounts of nutrients
as well as toxic substances have
been released which may have det-
rimental effects on living organisms
in terrestrial and aquatic ecosys-
tems.
In the past, nitrogen was the nu-
trient that most often limited forest
growth. Thus, it was assumed that
greater than normal atmospheric
deposition of nitrogen would stimu-
late increased growth in substantial-
ly the same way that urea and other
synthetic fertilizers applied through
the soil had been shown to do. But
now it is suggested that when for-
ests are continuously "fertilized from
above" that some detrimental ef-
fects could occur. Possible results
include:
• An elevated supply of nitrogen
could increase biomass produc-
tion to the extent that other ele-
ments such as magnesium,
phosphorus, or potassium be-
come limiting.
• Excess nitrogen could inhibit
synthesis of mycorrhizae.
• It could delay the formation of
cuticle or the transformation of
starches to sugars and thus
predispose the trees to frost, or
to winter dessication, or both.
• It could disturb the normal bal-
ance between shoot growth and
root growth in forest trees.
• It could change the susceptibility
of trees to pests and pathogens.
• It could increase leaching of ni-
trate to the soil when it can no
longer be fixed in biomass or
through denitrification.
• It could increase nitrification and
leaching of nitrates after accumu-
lation of exchangeable ammoni-
um ions. Nitrification and leach-
ing of nitrate lead to acidification
and loss of bases from the soil,
whereby a nutrient imbalance can
be intensified.
The biological effects of constant
increased atmospheric deposition
of nitrogen has been studied very
little. This is true for the study of
nitrogen metabolism of plants as
well as the nitrogen status of the
soil and soil organisms.
There was much discussion of this
hypothesis during the German-
American Scientific Exchange on V
Forest Decline. In spite of the lack V\
of experimental proof, this hypotheA
sis has been deemed so important
in the Federal Republic of Germany
that technical control measures for
nitrogen oxide emissions are now
being considered.
Hypothesis 6:
Organic Air Pollutants
Among the hypotheses discussed
here, the least definitive informationV.
is available regarding the possibility^
that growth-altering organic com-
pounds could be a cause of recent
forest decline. Professor Fritz Fuhr
of the Nuclear Research Center in
Julich called attention to their pos-
sible role because of the large
amounts of organic pollutants emit-
ted. It is possible that some among
the many thousands of organic
compounds present in the atmo-
sphere can have toxic or growth al-
tering effects on forest trees.
Organic compounds are emitted in
large quantities (in the Federal Re- \\
public about 1,6 million metric tons w
and about 20 million metric tons per
year in the United States) because
of their extensive use as solvents,
pesticides, as well as in numerous
chemical processes. Nature con-
tributes large amounts of organic
124
-------
Above:
Yellowing and necrotic discoloration
of fir needle tips. This damage symp-
tom is attributed to impact of ozone.
Left:
Yellowing of spruce needles. This da-
mage symptom is caused by magne-
sium deficiency. Only the adventitious
shoot is not affected.
Right:
Typical frost damage to red spruce.
The red-brown needles will drop dur-
ing the growth period. This time, the
buds have survived.
compounds to the environment.
However, there is limited informa-
tion available defining the spectrum
of compounds formed or detailing
the amounts present in air or in pre-
cipitation.
At present, only three compounds
have been seriously discussed -
ethylene, aniline, and dinitrophenol.
Exposure of loblolly pine to as little
as one part per million of aniline for
one hour has been shown to cause:
Abnormal (twisted) growth of pine
needles, abnormal dropping of pine
needles while still green, and killing
of some very sensitive pine seed-
lings. Ethylene is a very common
growth regulatory substance and
has recently been shown by Cana-
dian scientists to cause injury to
tree seedlings. Dinitrophenol has
been found in rain water samples in
Germany. It too is known to lead to
abnormal growth of plants.
Much more research is needed to
determine the possible biological
effects of various organic com-
pounds at concentrations that occur
commonly in air or in precipitation.
Thus, the search for phytotoxic
organic compounds in the atmo-
sphere continues. Special collec-
tion methods have been developed
for use in forest stands. The mea-
surement of deposition of organic
compounds to foliage is of primary
interest.
Friedland, A.J., Gregory, R.A., Karenlampi,
L., and Johnson, A.H., Winter damage
to foliage as a factor in red spruce decline.
Can. Journal Forest Research 14 (1984)
963-965,
Nihlgard, B., The ammonia hypothesis -
an additional explanation of the forest die-
back in Europe. Ambio 14 (1985) 2-8.
Prinz, B., Causes of forest damage in
Europe. Environment 29, No. 9 (1987)
11 -15 & 32-37.
Rehfuess, K.E,, On the impact of acid
precipitation in forested ecosystems.
Forstwiss. Centralbl. 100(1981)363.
References
Cheeseman, J.. Perry,TO. and Heck, W W.,
Identification of aniline as an air pollutant
through biological assay with loblolly pine.
Env. Pollut 21 (1980)9-22.
Cowling, E.B., Regional declines of for-
ests in Europe and North America: The
possible role of airborne chemicals,
pp. 855-864. In: Lee, S.D., Schneider, T„
Grant, L.D., and Verkerk, P.J. (Eds.),
Aerosols: Research Risk Assessment and
Control Strategies. Lewis Publishers,
Chelsea, Michigan, 1986.
/Schutt, P., and Cowling, E.B., Waldster-
ben, a general decline of forests in Central
Europe: Symptoms, development and
possible causes. Plant Disease 69(1985)
548-558.
Ulrich, B., Dangers for the forest ecosys-
tem due to acid precipitation. Landesan-
stalt fur Okologie, 9-25 (1982).
-------
Main Emphases
German-American Cooperation
H.E. Papke, B. Krahl-Urban und Chr. Schimansky
Julich Nuclear Research Center
Preceding chapters have presented
accounts of recent forest damage in
the Federal Republic of Germany
and the United States of America
and, with reference to specific sites,
have described the emphases of re-
search and the approaches adopt-
ed. The results to date indicate that
forest decline cannot be attributed
to one single cause. There are very
many factors to be discussed, each
with a different degree of signifi-
cance on individual sites. The pos-
sible causes of decline may be, ac-
cording to site, lack or disruption of
nutrition causing predisposition, cli-
matic factors setting oft the damage,
and biotic factors as accompanying
stress factors.
Nevertheless, to date there is no
evidence that the interplay of local
site factors and human-caused
stress factors alone could be
responsible for such widespread,
almost simultaneously appearing
forest decline in Central Europe and
North America. There seems to be a
further regional factor in the etiology
of the disease in Central European
and North American forests. Nearly
all scientists agree that recent forest
damage is a complex disease and
that injurious airborne pollutants
represent an additional, widespread
stress factor.
Research to date into forest decline
indicates many individual cause-
effect chains. The hypotheses de-
rived from these have proposed de-
tailed processes for individual
aspects of the development of the
damage. Here a discrepancy arises
in that on the one hand the hypo-
theses precisely describe the ef-
fects of the stress factors in detail,
but on the other hand, there are
great gaps in our knowledge of the
general functioning of an uninflu-
enced forest ecosystem. For even
in their final state, ecological sys-
tems are subject to natural varia-
tions, which are modified by a net-
work of stabilizing interactions.
Research into
Ecosystems
In future, as part of a policy of pre-
ventive environmental protection, in
attempting to overcome ecological
problems, research into ecosys-
tems will play a key role. Even today
a shift in the focus of scientific inter-
est towards ecological relationships
is evident in the field of environ-
mental research. Investigations so
far have been characterized by in-
tensive study of individual ques-
tions. However, site-oriented re-
search into forest decline, bringing
together up to twenty individual dis-
ciplines, has created the prerequi-
sites upon which later research into
ecosystems may be based. This is
very evident from the descriptions
of the research activity on the indi-
vidual sites.
Taking this as a starting point, initial
attempts are being made to deter-
mine the functional and structural
parameters of ecological systems
and to investigate their control and
feedback mechanisms. It is hoped
that barriers of knowledge between
classical disciplines can be over-
come by common research pro-
grams. Research into forest decline
has so far succeeded in a unique
manner in bringing together the var-
ious specialist disciplines of forest-
ry, physical and life sciences. The
development of ecological theory
is one of the greatest challanges in
basic research in ecology.
Research into Individual
Tree Physiology
Research into ecological systems
also includes the study of detailed
processes in the individual tree, and
such knowledge is needed as a key
to finding causes. Forest damage
research in the last eight years has
made it evident that the specific
principles of physiology, functional
anatomy and morphology of a heal-
thy tree are still very imperfectly
known. After intensive discussions
among experts, the German Re-
search Foundation (DFG) initiated a
new program with specific empha-
sis on physiology of trees. For the '
present this project is planned for
six years. It is anticipated to carry
it out in close conjunction with re-
search into forest decline.
German-American
Cooperation
Representatives of the Federal Re-
public of Germany and the United
States of America have spontane-
ously agreed on an exchange of in-
formation and on intensive scientific
cooperation, since numerous symp-
toms and suspected causes of
decline are similar in both countries.
This cooperation is to be promoted
by joint research projects and work-
ing meetings, To date, concrete
plans have been made for the over-
lapping research areas of atmo-
spheric processes and research
into the causes of forest decline.
126
-------
In the research area of atmospheric
processes, the following themes
will receive major emphasis in the
German-American joint project:
• standardization of measuring
techniques for dry and wet depo-
sition
• measurement of dry deposition
of gaseous pollutants
f improvement of measuring tech-
/ niques for injurious substances
in acid fog
• dispersion model for injurious air-
borne substances.
In the area of research into the
causes of forest decline, the major
themes to be emphasized in joint
research are stress physiology, the
rhizosphere, biotic damage factors,
and economic evaluation.
• stress physiology: Research into
the direct and indirect influences
of air pollution on the physiology
of individual trees. The reaction of
plants to acid input and assimila-
tion and food supply. Leaching of
nutrients from leaves and disturb-
ances in growth as the result of a
change in the distribution of assi-
milates.
• rhizosphere: Research into my-
corrhiza. Possible injurious ef-
fects due to the release of alumi-
num, due to acidification, and
other metal ions toxic to roots.
• biotic damage factors: Only a
very few highly specialised re-
search groups possess the tech-
niques to prove the presence of
viruses, viroids, bacteria, micro-
plasmas, rickettsia and other pri-
mitive microorganisms.
• economic factors: Methodologi-
cal difficulties due to inadequate
knowledge of the dynamics of
long-lived systems. Prognoses
on the economic loss to be ex-
pected from forest decline are
only possible to a limited extent.
Even during the 1984 excursions,
experts from the two countries dis-
cussed the possibility of close
cooperation in their respective re-
search areas. The first suggestions
for intensifying the exchange of in-
formation and joint projects were
presented to the German-American
Coordinating Committee at its first
meeting in May 1985. In the mean-
time many projects have already
started or are being planned in the
area of cause-and-effect research.
Forest Ecosystem Industrial Society
Emission of airborne
pollutants
Forest decline
Need for political actions
Unknown causes
National and international
regulations
Preventive care
Preventive care without
scientific background
No immediate success
Investements of billions $
Loss of billions $
Intensive Ecosystem
Research
Environmental policy based on preventive care requires action even when the
causes have not yet been scientifically established.
On the German side the Universi-
ties of Freiburg, Gottingen, Kassel
and Munich are involved. The Amer-
ican partners are scientists from the
following institutions: the National
Laboratories of Oak Ridge and
Argonne, the Universities of North
Carolina, Pennsylvania, Vermont
and Washington, as well as indus-
trial research institutes.
Prospects
Despite the intensive efforts of all
the scientific and political institu-
tions involved in seeking an expla-
nation for the causes of recent for-
est decline, not too high hopes
should be entertained of achieving
success. Research into cause-and-
' effect relationships in forest ecosys-
tems are extremely complicated,
very expensive and time-consum-
ing. The short-term goal should be
to develop and refine measures and
methods to shed light on individual
cause-effect relationships. How-
ever, in the long term, attempts
must be made on the basis of as-
sured knowledge to preserve and
improve forest ecosystems with
all their variety and their ecologic
and economic significance to Man.
There are numerous starting points
available for reaching these goals.
They will be reached faster if we
should succeed on an international
scale in bringing together the var-
ious scientific disciplines needed to
study the forest ecosystem. This al-
so includes industrial research into
preventing pollution, since man-
made impacts and injurious pollu-
tants are involved in forest decline.
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Explanation of Technical Terms
acid fog/acid rain In combustion pro-
cesses sulfur and nitrogen are oxidized to
-+ sulfur dioxide (S02) and -> nitrogen ox-
ides (NOx). Through chemical reactions in
the atmosphere they are changed into the
corresponding acids (sulfuric and nitric
acid), According to the moisture content of
the air or the size of the water drops, acid
fog or acid rain arises. Both have a nega-
tive impact on plant growth (destruction of
tissue, leaching out of nutrients, etc.) and
on soil conditions (-> soil acidification). In
acid rain or acid fog the -~ pH value can
drop to 2.0.
acids Chemical compounds which re-
lease hydrogen ions in aqueous solution
(-» pH value). The greater the concentra-
tion of the hydrogen ions released, the
greater the acidity and the lower the pH
value. Examples of strong acids are
-» sulfuric acid and -~ nitric acid, and of
weak acids: acetic acid and citric acid.
adventitious shoot An additional (out-of-
place) shoot which frequently sprouts only
after a wound or partial loss of the plant
body. This regeneration represents either
a replacement by sprouting of an already
formed dormant embryonic shoot or a
completely new formation.
alder (Alnus) The alder belongs to the
birch family and is found particularly in the
northern temperate zone. It is an important
deciduous tree for improving soil quality.
The symbiotic fungi living on its roots en-
able them to utilize airborne nitrogen.
The alder contains a bitter substance and
thus, although its bark is rich in protein, it
is seldom damaged by game. The major
species are red or black alder, white or
gray alder and green alder.
red or black alder (Alnus glulinosa)
Found all over Europe. It needs light and
requires high soil and air humidity. It is
thus a typical species in settlements near
rivers or groundwater. Its roots go down
as far as 4 m, and are hence the deepest
of all Central European species of tree. On
some sites the alder can reach a height of
up to 30 m, and its almost straight trunk
can reach a diameter of 60 cm.
white or gray alder (Alnus incana) This
tree is found often along alpine streams in
the northern part of Europe and Asia and
in North America. It resists frost and has
considerably lesser demands regarding
nutrients and soil moisture and is thus
suitable as a -> pioneer species on many
sites.
green alder (Alnus viridis) The green al-
der is found in high mountain areas on
loamy-clayey soil on steep sites, where it
replaces the ->• mountain pine. It grows to
a height of only a few meters. It prevents
soil being carried away and -~ erosion in
avalanche prone areas. Under its foliage
Norway spruce and larch find favorable
conditions for regeneration.
amelioration Measures to improve soil
utilization, e.g. irrigation and drainage, cul-
tivation and recurvation, -+ fertilizer, til-
lage, etc.
annual rings Zones of growth seen on
the cross section of a tree trunk, formed
by the periodic activity of the cambium at
different seasons. In the northern hemi-
sphere of the Earth, wood formation usu-
ally ceases in the second half of August;
thus between the late wood and the early
wood from the next year there is a sharp
delineation. From the number of annual
rings, the age of a tree can therefore be
calculated.
ash (Fraxinus) The ash belongs to the
olive family and is mostly found in north-
ern temperate zones. The major species
are common ash and white ash.
common ash (Fraxinus excelsior) This
-> hardwood is found all over Germany
except on low base (under pH 4.5) soils
and soils low in nutrients. It supplies valu-
able timber and lumber. When young, the
Adventitious shoot sprouting from an
almost dead tree.
common ash tolerates a moderate amount
of shade, but later needs a lot of light. It
lives 200-300 years and reaches a height
of up to 35 m.
white ash (Fraxinus americana) Of all the
ash species in the Appalachians (exclud-
ing the mountain ash), the white ash is the
only one found in forests on normal sites
and in the montane stage. It is used in the
manufacture of furniture and because of its
big leaves, which turn purple or yellow in
autumn, it is ornamental in gardens and
parks.
aspen (Populus tremula) The aspen is a
type of poplar found in Europe and North
America. It is a true -» pioneer species,
settling on sites from the lowlands to sub-
alpine regions preferring rich soils and
sufficient light. Its roots penetrate into peri-
odically moist soil. It reaches an age of
only 80 years and a height of up to 28 m.
The wood is considered of little value.
When young, it grows very fast, but is
much damaged by game and beaver, and
in many forests is therefore only found
when protected from game by fences.
association of plants A group of differ-
ent species of plants with given site condi-
tions. Each individual combination allows
one to draw conclusions about the -~ site
and the potential natural vegetation. This
knowledge is important for the mainte-
nance of a naturally managed forest
beech (Fagus) Only one species of
beech is found in Europe, the red beech
The American beech belongs to the same
genus, the species name is grandifolia.
red beech (Fagus silvatica) The red
beech was the naturally most frequently
occurring species of tree in Central Eu-
rope. In its youth the red beech grows rel-
atively slowly, but it continues to grow (up
to 40 m) even when aged. It can reach an
age of 300 years. Its natural regeneration
is difficult since young red beech is more
frequently attacked by animals than coni-
fers.
american beech (Fagus grandifolia) The
American beech is found in Atlantic North
America from the lowlands to the high-
montane level. Fagus grandifolia also ex-
tends to the southern limit of the decidu-
ous forests and forms there, in the north of
Florida, mixed stocks with the evergreen
-» Magnolia grandiflora.
biotope The biotope is the natural living
area of a settled grouping of plants and
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animals living together (-» biozoonosis).
The biotope is characterized by the abiotic
features of the site.
biozoonosis A society of the regularly
occurring living forms of various kinds
found together in a biotope.
birch (Betula) Deciduous trees or shrubs
found in the cold zones. The major spe-
cies are white birch, sand birch, moor
birch, yellow birch and cherry birch. Horn-
beam (Carpinus betulus) also belongs to
the birch family.
white birch (Betula verrucosa) The white
birch is found in Central Europe particu-
larly on poorer sites. It reaches an age of
about 100 years and a height of up to
30 m.
sand birch (Betula penduta) The sand
birch is found all over Germany, especially
on sandy soil. It frequently occurs with
oaks.
moor birch (Betula pubescens) The moor
birch is found mainly on low-lying moor-
land areas, but also on the coast and on
the alpine treeline.
yellow birch (Betula lutea) The yellow
birch is the main species found at the high
montane level of the Appalachians. Also in
mountain conifer forests, where it regularly
appears scattered, it is a -* pioneer spe-
cies, often germinating on rotting
branches and trunks in large quantities,
but flourishing only where there is light.
black birch (Betula tenia) The black birch
is found in North America in mesophile
forests at the montane and submontane
levels, where it flourishes in the gaps left
by disappearing chestnuts. It also plays a
part in submontane riparian meadows.
buffering capacity The ability of a sys-
tem, here the soil, to maintain its -» pH val-
ue practically constant, even under the in-
fluence of acids or bases. Soils containing
calcium carbonate have high buffering ca-
pacity or capability. Chalk (CaC03) reacts
with acids (H4 ions) and creates harmless
carbonic acid (H2C03) which reduces to
water and carbon dioxide. However many
soils contain no chalk. Silicates can also
act as acid buffers, but they react very
slowly and therefore cannot buffer large
quantities of acid within a short period.
Here a surface layer of clay particles is
helpful. These contain basic calcium
(Ca2+) ions and magnesium (Mg2+) ions
which are in balance with the soil solution.
When there is acid input into the soil the
Ca2+ and Mg2+ ions are displaced from
the surface of the clay particles and ex-
changed for H+ ions. If these acids cannot
be reduced in the soil and exchanged
back, then as more acid is input, greater
quantities of acid accumulate on the sur-
face. of the particles and thus gradually
displace the important nutritive ions of
Ca2+ and Mg2+ into the soil solution. This
ion exchange indeed buffers the acid, but
the soil loses its basic nutrients, which are
washed out of the soil as water trickles
through.
cherry (Prunus) This tree is frequently
found in the lower mountain ranges of Eu-
rope and North America. Major species
are the fire cherry and black cherry,
fire cherry (Prunus pensylvanica) Typical
-t pioneer tree found in the American bo-
real conifer forests as far north as Alaska,
and flourishing strongly particularly after
major forest disturbances like fires or log-
ging. For instance there are large stocks
which have replaced destroyed spruce-fir
forests near Mount Mitchell. In the mon-
tane zone, this species is also common
on forest edges.
chlorosis Decline or loss of chlorophyll,
the green matter found in leaves. Causes
may be lack of minerals, climatic influ-
ences and other factors. Pollutants can
also lead to chlorosis. However, chlorosis
is not specific, and conclusions can only
be drawn in respect to characteristic
-~ necrosis.
Clean Air Act Under the Clean Air Act of
1963, as amended in 1970, state and local
governments have primary responsibility
for the control and prevention of air pollu-
tion in the United States. The Environmen-
tal Protection Agency (EPA) is responsible
for setting national standards to protect
public health and welfare, conducting re-
search on prevention and control of air
pollution, and providing technical and fi-
nancial assistance to state and local gov-
ernments for air pollution control. EPA has
set National Ambient Air Quality Stan-
dards (NAAQS) for following air pollutants
most widespread throughout the country:
ozone, carbon monoxide, total suspended
particulates, sulfur dioxide, lead, and ni-
trogen dioxide. Each state must draw up a
State Implementation Plan describing how
it .will control emissions from mobile and
stationary sources in order to meet the
NAAQS. The Amendments also require
EPA to review and regulate hazardous air
pollutants. EPA has already issued stan-
dards for four of the pollutants: asbestos,
beryllium, mercury, vinyl chloride, radio-
nuclides, and benzene.
cuticule A layer on the surface of cells
which is only semipermeable for water
and gases. It helps plants to avoid dam-
aging water loss as a result of excessive
transpiration. In some plants the cuticule
has a waxy layer on the surface.
denitrogenation of flue gas The most
used flue-gas-denitrogenation process is
the selective catalytic reduction. In large
chambers containing honeycomb-formed
catalists flue gases react with ammonia
water spray to form nitrogen and water.
This process reduces the nitrogen oxide
concentration in the flue gases by 90%.
deposition The input of emitted pollu-
tants (-~ emission) via air or water to soils,
in terrestrial and aquatic ecosystems and
to buildings.
desulfurization of flue gas When fossil
fuels (e.g. coal, oil, gas) are burned, flue
gases are given off. These flue gases con-
tain a large proportion of -f sulfur dioxide
(SO2) and sulfur trioxide (SO3). In flue-gas-
desulfurization the acidic sulfur oxides are
removed from the flue gases by reacting it
with an alkali. The various desulfurization
processes available differ in the alkali
used, the method of contacting the gas
with the alkali and the way in which the
product is treated. The most commonly
used alkali is lime or limestone as an
aqueous slurry which removes sulfur ox-
ides in a wet absorber. In this process
gypsum (CaS04 • 2H20) is produced as
the final product.
detrivores These organisms decompose
all organic waste products of the forest
and loosen the soil. As the organic sub-
stances decompose stage by stage, inor-
ganic substances are created (mineraliza-
tion) which the plants can utilize. In one
cubic meter of soil over 200 earthworms
and several million threadworms and
several hundred thousand mites and
springtails may live. Also, in a gram of soil
there may be up to a billion bacteria, blue
algae, actinomycetes and fungi
dogwood (Cornus florida) The dogwood
is a species found at lower elevations in
the Appalachians. Dogwood usually has
the form of' a tree, but does not grow
higher than 15 m and never reaches the
canopy. Midspring it blossoms brilliant
white. Dogwood is a very hardy plant and
adapts well to any kind of soil.
Douglas fir (Pseudotsuga menzit) This
conifer from the west of North America has
been cultivated in Germany since about
1880. The wood is similar to that of
-~ larch. The greatest success with it, with
twice the growth rate of spruce, has been
in Atlantic climates (small temperature dif-
ferences between summer and winter) on
sandy loam hospitable to the roots. In
Germany, Douglas fir has sharply in-
creased in recent years, because it can
survive bark damage by game without
much loss of wood. The share of Douglas
fir in German forests is about 1%; in young
Rhineland Palatinate forests (1-20 years
old) its share is already 20%.
dry deposition Deposition on surfaces
by adsorption, sedimentation or absorp-
tion. During long, dry periods consider-
able quantities of pollutants can collect on
leaves, needles or bark, and go into solu-
tion when there is dew or rain.
earthworms The best known representa-
tives of life in soil. They help turn plant re-
mains into humus which generally im-
proves soil structure and consequently im-
proves soil aeration, soil drainage and wa-
ter infiltration rates. Earthworm activity is
strongly correlated with soil-pH. In natur-
ally acidic forest soils their numbers are
insignificant
ecological niche Refers to the role and
(unction of a species in the -> ecosystem.
The concept of the ecological niche de-
scribes the precise relationship of a spe-
cies with its environment. Niche finding is
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the most effective way of avoiding compe-
tition and enables the coexistence of
many species in the same -> biotope.
ecology A field of biology. It is the
science of the interrelationships between
organisms and their environment, of mate-
rial and energy flow within the biosphere.
elm (Ulmus) There are three varieties in
Central Europe: the mountain elm, the
Russian white elm and the English elm.
While the mountain elm is found espe-
cially in mixed woods with many beeches,
the Russian white elm is found in meadow
forests with oaks and the English elm in
mixed oak woods on the plains. The elms
are threatened with extinction by Dutch
elm disease, the elm bark beetle, which
blocks the flow of water in the wood
emission The anthropogenic release of
substances in flue gas, exhaust air, waste
water, and solid and liquid wastes. Emis-
sions from natural sources include the
gases from volcanos and chemical sub-
stances released to the environment by
plants and animals.
enzymes Biocatalysts produced by living
cells which make possible, speed up or
control chemical reactions.
erosion Removal of soil by water and
wind. Flowing water washes the soil away,
especially on sloping ground with little
plant cover. Wind works most on flat areas
with low vegetation. Any growth (e.g. for-
est or hedges) can protect the ground
from erosion.
exchange capacity The exchange ca-
pacity is the sum of the equivalents of the
cations which at a given -~ pH value of the
soil can be replaced by a neutral salt solu-
tion.
fertilizer Plays a small role in forestry as
compared to agriculture, since little bio-
mass is removed. However, a precondi-
tion is that bark and branches remain, and
that only trunks are harvested. In these cir-
cumstances the food balance is preserved
via the weathering of rock and input from
the atmosphere. Fertilizer is therefore
used only on the poorest sites, where for
instance -» foraging has removed many
nutrients from the soil, or it may also be
taken to stimulate the decomposition of
humus or to give cultivated stock a better
start, In relation to -» forest decline fertili-
zer may be used:
- to counteract increasing -» soil acidifi-
cation and disruption in the nutrient
supply;
- to activate the soil fauna, to speed the
decomposition of litter and surface hu-
mus.
fir (Abies) Differs from spruce in that the
needles of fir are on little pads on the
twigs. Fir cones are upright, and decay on
the tree. The most important species in
Central Europe is silver fir, and in the Ap-
palachians balsam fir and Fraser fir.
Lichens can be used as bioindicators
for airborne pollutants.
silver fir (Abies alba) The mightiest tree in
Europe, living 600 years and reaching a
height of more than 65 m. It is mainly
found in southern Germany. Because it
forms a tap root it is less liable to storm
damage than other trees. The silver fir is
very tolerant to shade and the most im-
portant species of the -» uneven-aged for-
est. On many clayey soils it is essential for
the stability of the forest and the protection
of lower lying sites. However it is endan-
gered by -» game damage and in the last
150 years has lost share most consider-
ably in mixed mountain forests.
balsam fir (Abies ba/samea) This North
American fir grows up to 25 m high and
has a smooth black bark. It is part of the
boreal forests in the North Appalachians
and Canada.
Fraser fir (Abies fraseri) It occupies only
a very small area in the states of North
Carolina and Tennessee at levels over
1500 m. Compared with other species of
fir, its vitality is low. Heights over 20 m are
rarely reached, It is difficult to cultivate:
even at lower elevations (about 1000 m).
Natural stocks have also been severely
damaged in many places by the balsam
wooly adelgid from Europe.
forest damage Describes a complex de-
cline syndrome that has been observed
for several years in the forests of Central
Europe and North America. In Europe, it
does not consist of damage of individual
species, but represents a disturbance to
the relationship of tree-soil-air, and thus a
decline of the entire forest -> ecosystem.
forest of different age classes Cultivated
forest with a chessboard pattern of
stocks of various ages. The individual
groups represent 20-year steps, and an
even distribution of age groups is aimed
at More than 95% of the forests in the
Federal Republic of Germany today have
such a structure (-+ uneven-aged forest,
-» naturally cultivated forest).
game damage Wild animals (deer, stag
and chamois), and occasionally hares and
rabbits bite off buds, shoots and leaves
from shrubs and young trees.
growth of wood Growth depends on site
conditions, the genetic characteristics of
the tree, and the age of the tree. The rate
at which wood grows varies in Central Eu-
rope and North America between 3 and
20 m3 per hectare. The -» light-loving and
-~ pioneer species attain their fastest rate
of growth very early, while -> shade-loving
trees such as silver fir and red spruce are
capable of spurts of growth even at great
age. -~ Forest damage has frequently led
to a decline in growth.
hardwoods Deciduous trees which yield
valuable wood for utilization, and whose
easily decomposed leaves help humus
formation. Hardwoods usually make high
demands as to the quantity of nutrients
and water. Hardwoods include beech,
oak, ash, maple, lime, elm and wild cherry.
heavy metals ¦ Metals with a density of
over 4.5 g per cm3. Some are nutrients
(zinc, iron, manganese, copper, etc.) and
some toxic (cadmium, mercury, lead, etc.).
Heavy metals in compounds are natural
components of the Earth's crust. In var-
ious ways (-* emission, waste water,
combustion) they reach the environment
and can be problematic in soil (i.e. when
available to plants in concentrations which
are toxic).
hemlock (Tsuga) The hemlock in the Ap-
palachians is a typical species of the
transitional region between deciduous
and coniferous forests. In the South Ap-
palachians it occurs at higher elevations
than the eastern white pine, but it plays no
part in the high-montane transitional zone.
herbaceous layer Plants ol the forest
floor In unbroken forests, far fewer herba-
ceous plants grow than in the open. Ac-
cording to the amount of light and the
-» site, different societies of plants arise.
-» lichen, fungi, -» mosses, ferns, flowers
and grasses.
high output furnace regulations In these
regulations, which come under the
-~ Federal German Immission Protection
Law, are limits for -> emissions of acid
forming substances and those containing
-> heavy metal pollutants from high output
furnaces (power plants with an output of
over 50 MW(th)). The primary intention of
these regulations is to reduce the long-
distance transport of pollutants and hence
the stress on the forests
hornbeam (Carpinus betulus) The horn-
beam originally grew in warm mixed oak
forests and in -» riparian forests Because
of the ease with which it sprouts from
shoots, it has proliferated in low-lying and
mountain forest areas. In Germany it
reaches an age of about 150 years and a
height of up to 25 m. When young, it
grows faster than the red beech and al the
age of 10 is already up to 6 m high. The
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hornbeam's bark is very susceptible in its
youth to damage by game.
humus A general term for well-decom-
posed organic matter in soil subject to
constant processes of decomposition,
transformation and reformation. The
amount and chemical characteristics of
humus are affected by factors such as cli-
mate, vegetation, soil fauna, moisture
level, -~ pH value and calcium saturation.
According to how it is decomposed, var-
ious forms of humus can be formed on the
soil's surface: mull (organic horizon of hu-
mus incorporated into surface mineral
soil) or mor (raw humus; unincorporated
and usually compacted matter lying above
and distinct from the mineral soil).
Immission Protection Law This law is
the Federal Republic of Germany's legal
basis "for protection against injurious in-
fluences on the environment from airborne
pollution, noise, vibration and similar pro-
cesses". It contains requirements (-~ state
of the art, polluter pays principle) and ad-
ministrative regulations for the licensing,
operation and cleanup of emitting plants
(-~ desulfurization, -> high output furnace
regulations); environmental planning, and
provides a basis for legal regulations and
administrative instructions regarding im-
mission protection.
larch (Larix) This is a conifer which turns
green in summer and belongs to the pine
family. It occurs naturally in Europe in the
higher alpine forests. A few are still lound
in the Sudeten and Carpathians. The larch
reaches an age of 400 years and a height
of up to 45 m. It has formed strips on
many kinds of sites. In the last 200 years it
was artificially cultivated on a wide scale in
deciduous forests. The larch is an extreme
-~ light-lover and needs low-lying con-
stantly cool sites. Because of its long-last-
ing and attractively grained wood it is very
popular. It is a valuable addition when
mixed with fir, spruce and pine. The larch
is often endangered by pests. When
young it is frequently damaged by game.
Japanese larch (Larix leptolepis) A non-
native (from Central Japan) that has been
cultivated since the end of the 19th cen-
tury particularly in afforesting North Ger-
man heaths.
lichen An association (-> symbiosis) of
algae and fungi. Some species are very
susceptible to pollutants: they therefore
function as bioindicators showing the ex-
tent of certain forms of airborne pollution.
light-lover These tree species are more
shade intolerant than -» shade-loving
trees and therefore do not grow well under
a forest canopy. Examples of light-loving
trees are pine, birch, aspen and larch, as
well as alder.
linden or basswood (Til/a) Some 25 spe-
cies of linden tree are found in the north-
ern temperate and subtropical zones. The
linden reaches an age of 1000 years and
achieves very large crown diameters, up
to 20 m It has a very marked heart root
system and, especially in its youth, is very
tolerant to shade. It is damaged by game
less than other -• hardwoods, but red
deer like to strip the bark. Only two spe-
cies are native to Germany, the winter lin-
den and the summer linden. In North
America the American basswood is
frequently found.
winter linden (Titia cordata) Prefers mixed
deciduous forests on plains and hills that
are warm in summer.
summer linden (Tiiia platyphyl/os) Is
found in harsh environments with beech
up to mixed mountain forests,
American linden or basswood (TiHa ameri-
cana) The basswood is the most impor-
tant linden species in the Appalachians. In
its natural habitat it can reach a height of
40 m.
litter utilization Litter from the forest is
used as forage to substitute for straw in
cattle sheds. It was practiced formerly in
Germany, particularly in regions with poor
soil, such as the Upper Palatinate, Lune-
burg heath or the Palatinate Forest. Thus
important nutrients were removed from the
forest, leading to -> soil acidification, de-
creased growth and a general weakening
of the forest (-~ amelioration, -» fertilizer).
magnolia (Magnolia traseri) There are
some 75 species of magnolia in Eastern
North America and East Asia. Magnolia
fraseri is characteristic of the galax red
oak forests in the South Appalachians. It
only occurs sporadically in other types of
forests. With a single trunk the magnolia
can reach a height of 25 m, but it often
grows with several trunks and remains
lower.
maple (Acer) Trees and shrubs of the
aceraceae family, found in Europe, Asia
Minor and North America. The major spe-
cies are mountain maple, Norway maple,
field maple, red maple and sugar maple.
mountain maple (Acer spicatum) A decid-
uous tree found as a component of mixed
deciduous forests on nutrient-rich sites,
from riparian woods to high mountain re-
gions. When young, it is shade tolerant
(-~ shade-lover), grows up to 35 m high
and can live up to 300 years. Because of
its rapid growth and the fast transforma-
tion of its foliage to humus (2 years) it is
one of the most important trees for provid-
ing rapid ground cover and soil improve-
ment in old, damaged forests.
Norway maple (Acer platanoides) It is
found individually in mixed oak woods. In
Central Europe it normally reaches a
height of 20-25 m and an age of about
100 years. Because of its ability to regen-
erate by -~ adventitious shoots and the
fast decomposition of its leaves, in forest
regeneration it is of similar significance as
mountain maple.
field maple (Acer campestre) A relatively
slow growing tree. It reaches a height of
only 15 m and lives up to 150 years. Be-
cause of its ability to withstand moderate
shade it is suitable for stepped forest
edges and windbreaks.
red maple (Acer rubrum) The red maple
is more tolerant to harsh (especially nu-
trient poor soil) site conditions than is
mountain maple. On the best soils (nu-
trient rich sites) it cannot withstand the
competition of other species, but when
there is thinning it quickly flourishes. In
North America it is found in valleys and up
to mountainous areas.
sugar maple (Acer saccharum) The sugar
maple is the main species in the montane
deciduous forests on the richest sites
Under-story vegetation needs very little solar radiation to grow on the forest floor.
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throughout the Appalachians and South
Canada. It grows to a height of up to 30 m
and is found in association with yellow
birch, American beech and ash. Maple
sirup is regularly harvested, especially in
nothern latitudes. No effect of air pollution
on sirup production has been demon-
strated unequivocably.
mosses Spore plants. There are about
2500 species which are grouped with the
ferns as archegoniates. Mosses differ
from ferns in that they lack proper roots
and vascular tissues. They grow on the
forest floor, on rocks or fallen trees, and
need very little light.
mountain ash (Sorbus) Pioneer species,
which grows to a height of up to 20 m, is
particularly frost resistant and tolerates nu-
trient poor soil. There is an American and
a European species.
European mountain ash (Sorbus aucupa-
ria) This species is widely distributed in
Europe, including high mountain ranges
together with spruce. As a -» pioneer spe-
cies it grows very quickly when young, but
reaches an age of only about 120 years.
Mountain ash is gaining increasing signifi-
cance in the slowly dying old European
forests as it helps secure and improve the
soil.
American mountain ash (Sorbus america-
na) The American mountain ash is very
similar to the European species. Individ-
uals are growing at the conifer level. It is
found quite frequently at forest edges and
where there is a transition to forest vegeta-
tion.
mycorrhiza This is the term for a -» sym-
biosis of fungi and roots of higher plants;
for some tree species (e.g. pine) mycor-
rhiza is a vital element. There is a mutual
exchange of materials between fungus
and routs: the fungi obtain carbohydrates
derived from photosynthesis and metabo-
lism in higher plants, while they give water
and nutrients to the roots.
natural forestry It endeavours as far as
possible to avoid unnatural intervention in
the forest. It rejects clearcutting, wood
plantations, the use of large machines and
pesticides. It relies on -» natural regenera-
tion appropriate to the site, combinations
of tree species as found in nature, careful
rearing of young trees with some shade
from the older trees and cutting only of in-
dividual trees to optimize the increase in
value of older trees.
natural regeneration Regrowth of a for-
est with its own seeding, sprouting of
shoots, etc, as in nature. Modern forestry
seeks to rely on natural regeneration as
much as possible.
necrosis Area of dead cells or tissue
within a living organism. In plants necrosis
can occur as the result of the action of pol-
lutants The location and color (symptom-
ology) of the necrosis may provide some
evidence as to the type of pollutant.
nitric acid HN03, is the most important
acid of nitrogen, and one of the strongest
inorganic -> acids. Nitric acid is used in
the production of some nitrogen fertilizers.
Nitric acid is created from reaction of NO*
in the atmosphere with -+ photooxidants
and water. Nitric acid is introduced into
forest ecosystems via alternatively bulk
precipitation and dry deposition.
nitrogen oxides (NO.) Nitrogen monox-
ide (NO) and nitrogen dioxide (N02). They
are formed in all combustion processes
as compounds of nitrogen and oxygen. In
air NO quickly becomes NO2, from which
in turn -~ nitric acid, a co-producer of
-~ acid fog and acid rain, can form. Nitro-
gen oxides can also react under the influ-
ence of sunlight to produce -» photooxi-
dants, e.g. -+ ozone.
oak (Quercus) Oaks are native to North
America, Europe and western Asia. Be-
sides red beech, oak was formerly the
most frequently found deciduous tree in
Germany. With a long life span (800 to
1000 years) it can provide valuable and
long-lasting wood. The major species are
European oak, sessile oak, northern red
oak, scarlet and white oak.
European oak (Quercus robur) Is found
in Europe, especially on plains and in
-» riparian forests (recognizable by acorns
on long stems).
sessile oak (Quercus petraea) Can be
found mainly on hills and lower mountain
slopes in Central Europe. The valuable ve-
neers supplied by the sessile oaks of the
Spessart and the Palatinate Forest are
worldfamous.
northern red oak (Quercus rubra) On
poor sites the northern red oak is the most
important and most competitive of the four
oak species in Eastern North America. It
was also introduced into Germany be-
cause it is tolerant to sites which are not
nutrient rich and grows faster than the na-
tive oak species. Because of its resistance
to storms it is the most sturdy non-native
variety in the Federal Republic. Since ex-
perience to date suggests it is also less
affected by air pollution, it could become
an important species for mixed forests on
poor soils and in deforested areas.
scarlet oak (Quercus coccinea) Scarlet
oak characterizes the pine-oak forests of
the submontane stage of the Appala-
chians with extremely poor soil. Here it is
mostly a low, poorly formed tree, but it can
also reach a height of over 25 m on better
sites.
white oak (Quercus alba) The white oak
is without doubt the most beautiful of the
oak species found in the Appalachians.
Their broad round crowns make lone
standing trees very impressive, particu-
larly in gardens and grounds. It is not
tolerant to poor soil conditions.
ozone 03 arises from the effect of ultra-
violet light in the Earth's upper atmo-
sphere, but is also formed when -» nitro-
gen oxides and hydrocarbons come to-
gether under the effect of sunshine. O3 is a
strong oxidant, which can harm Man,
plants and materials.
pesticides Generic term for all chemical
substances used to protect plants from
disease (microbial agents) or herbivory
(insects).
photooxidants Generic term for com-
pounds that can be formed from -» nitro-
gen oxides or hydrocarbons under the in-
fluence of sunlight. Among these are
-+ ozone, peroxiacetylnitrate, -» nitric acid
and other products of reaction. Frequently
only the concentration of the leading
photooxidant, ozone, is measured. In con-
trolled laboratory and recent field chamber
studies, photooxidants have been shown
to damage vegetation. They may be co-
responsible for -> forest decline.
photosynthesis Green plants use sun-
light, carbon dioxide from the atmosphere,
water and the green pigment in their
leaves, chlorophyll, to make glucose. In
this process, oxygen is released. Photo-
synthesis may be regarded as the most
important biochemical process on Earth.
Forests use about 2-3% of the incoming
sunlight for the production of organic sub-
stances. The worldwide net production
from photosynthesis is estimated at
100-300 billion tons of dry weight per
year.
pH value It is defined as the negative
common logarithm of the hydrogen ion
concentration. It represents the concentra-
tion of free hydrogen ions in a liquid. The
neutral point is at the pH value equal to 7.
An increase or decrease by one point indi-
cates that the liquid has become more al-
kaline or more acid by a factor of 10.
phytohormones (plant hormones) Plant
hormones are substances which even in
small quantities can set off and control
certain physiological reactions such as
growth, stretching of cells, rhythm of
blooming, division of cells, healing of
wounds, ripening of seed, rendering seed
dormant, etc.
pine (Pinus) Conifer found mainly in the
northern temperate zone, thriving particu-
larly on poorer sites. The major species
are Scots pine, mountain pine, Swiss
stone pine, black pine and eastern white
pine. In the U.S, there are several other
species which are important in the lower
elevations of the Appalachians.
Scots pine or common pine (Pinus s/lves-
tris) The Scots pine occupies about a
quarter of the forest area of the Federal
Republic of Germany It can live 400 years
and reach a height of up to 40 m. Large
areas of pure stock of the same age are
severely endangered by snow, insects
and fire.
European mountain pine (Pinus montana)
The European mountain pine is bushy and
is an important -» pioneer species on the
more extreme parts of the Alps and some
132
-------
lower mountains. There it forms unbroken
shrubbery above the timber line.
American mountain pine (Pinus pungens)
The American mountain pine is a small
species found in the southern Appala-
chians and the foothills.
Swiss stone pine (Pinus cembra) It is
found in Central European high mountain
areas, with an important protective func-
tion at the timber line.
black pine (Pinus nigra) The black pine
comes from southwest Europe and is
planted for reforestation of level, chalky
sites. It is less sensitive to deposition of
airborne pollutants than other conifers.
short leaf pine (Pinus echinata) This spe-
cies is one of the principal coniferous
trees of the southeastern United States
and of major economic importance. Its
name has derived from the fact that the
leaves are flexible and short. The wood is
yellow and the bark cinnamon colored.
eastern white pine or Weymouth pine (Pi-
nus strobus) The eastern white pine is
found in the North Appalachians in the
transitional region between the deciduous
and coniferous forests and in the South
Appalachians, as a rule only below
1000 m. It is not limited to extreme sites,
but is also found in oak forests on sites of
moderate quality. Formerly eastern white
pine was much used in Europe for
reforestation on poor soil. However, since
1854, it has been attacked by a fungus,
bladder rust, which reduces the value
of the wood; therefore it is now being
planted less.
pioneer species Trees which are adapt-
ed to the soil and climatic conditions ol a
site and which can therefore quickly
establish themselves in thinly populated
sectors or open ground. They include,
among others, willow, aspen, alder, birch,
mountain ash, pincherry, striped maple,
etc. Pioneers grow fast and their foliage
decomposes easily. They therefore aid the
formation of mild -> humus, prevent hu-
mus and soil from disappearing, and so
are very important for the protection of the
soil (-» erosion) and the reforestation of
damaged forests
poplar (Popuius) Poplars are found all
over Europe, North America and Asia, and
mostly on damp or wet sites. Common in
Germany are the silver poplar, the black
poplar, the aspen and various cultivated
species. They grow fast, but the light,
tough wood is of low quality.
ppb Abbreviation for "parts per billion",
this is one part in every billion parts, e.g.
1 microgram per kilogram (ng/kg).
ppm Abbreviation for "parts per million",
this is one part in every million parts, e.g.
1 milligram per kilogram (mg/kg).
regeneration The natural or artificial re-
placement of an old generation of trees
with a new one. In -~ natural regeneration,
the young trees arise from fallen seeds,
¦
Spruce shows abundant cone produc-
tion every five to six years.
shoots or from the roots of old stock,
while in artificial regeneration young trees
are planted or seeds sown. In practice var-
ious methods of regeneration are used,
mostly in combination, e.g. shelterwood,
edge, progressive or femel strip system.
rhizosphere Area of soil influenced
physiologically, chemically and biologi-
cally by plant roots.
rhododendron (Rhododendron caienduia-
ceum) This deciduous relative of the aza-
lea is frequently found in the montane
chestnut-red oak forests of the Appala-
chians.
roblnia (Robinia) Is usually found individ-
ually in many forest types at the montane
level and lower in the Appalachians. It only
occurs in higher densities after deforesta-
tion. The most frequent species is the
common robinia (Robinia pseudoacacia).
seed year The seed production of the
various tree species is not constant from
year to year. There are main seed years
for elm, maple, ash and basswood every
three to four years; for spruce, fir and
beech only every five to six years, and for
oaks on cooler sites every six to twelve
years. Between seed years there is lower
seed output. However, -» pioneer species
such as aspen, mountain ash, willow and
alder bloom and fruit every year.
shade-lover These trees are more shade
tolerant than -~ light-loving trees. Shade-
lovers include yew, fir, beech, oak, and
to a lesser extent, spruce, Douglas fir,
basswood, elm, mountain ash, eastern
white pine and Swiss stone pine.
site A site is characterized by the totality
of all independent climatic, soil, geologic,
topographic and biotic factors acting on
the plant in its environment, The form and
structure of an association of lifeforms on
a particular site depends directly on these
five factors and the age of the site (since
the deposition of parent material).
snow breakage Is the result of too great
a weight of snow on a tree causing the
breakage of the crown. Conifers are more
susceptible than deciduous trees, which
are bare of leaves in winter. In particular,
young, close-growing conifer -» monocul-
tures at high altitude can completely col-
lapse under snow.
soil acidification By soil acidification is
understood a far-reaching replacement of
exchangeable ions of calcium, magne-
sium, potassium and sodium by hydrogen
and aluminum ions on soil surfaces. This
is initiated by a number of natural pro-
cesses and anthropogenic inputs such as
the formation of carbon dioxide in respira-
tion, biologically mediated organic matter
decomposition and mineral transforma-
tions, the exchange of hydrogen ions for
nutrient cations during plant nutrient up-
take; the formation of -+ acids, especially
-+ sulfuric acid and -+ nitric acid; by the
use of physiologically very acidic fertilizers
such as ammonia and ammonia-forming
urea fertilizers; by acid input from the air-
borne pollutants via precipitation and dry
deposition; release of aluminum ions from
the crystal lattices of clay minerals via free
acids. The result is loss of -<• buffering ca-
pacity of the soil, increase of the concen-
tration of hydrogen and aluminum ions,
damage to root, plant growth and to the
life of the forest floor.
spruce (Picea) These conifers are found
all over the northern temperate zone. The
most important species are the Norway
spruce and the red spruce.
Norway spruce (Picea abies) Originally
the Norway spruce was found only at me-
dium and higher levels of the high moun-
tain areas and on the tops of hill ranges. In
its home area it can reach an age of 600
years, but on unsuitable sites and in pure
stands it may reach only 60-80. The Nor-
way spruce reaches a height of up to
40 m Its roots are mostly superficial but
form tap roots at low elevations. The nee-
dles do not decompose easily. When it
forms pure stands outside its natural
range it often creates thick raw humus car-
pets. There it is also severely threatened
by storm, -> snowbreak, red ring rot and
bark beetle. The Norway spruce is very
easy to cultivate and plant; it is less sus-
ceptible to damage by game than are
other tree species. On suitable sites, parti-
cularly when mixed with deciduous trees
and firs, it is a very productive species for
lumber.
red spruce (Picea rubens) Red spruce
occurs naturally in the northeastern United
States and adjacent Canada, it extends
southwards along the Appalachians into
North Carolina. Its wood is most favored
as lumber and used for paper pulp. Red
spruce makes up about 80% of the east-
ern spruce volume.
133
-------
stand A relatively unified piece of forest,
representing the smallest unit for silvicul-
tural management, based on shape and
size (more than one hectare).
stand management The management of
a stand with the aim of producing as much
valuable wood as possible. Such mea-
sures include favoring the most suitable
and best shaped trees, cutting others and
in some cases promoting certain species
(e.g. cutting beeches to favor oaks).
stomata Cells in pairs which can open
and close for the transport of gases and
the release of water vapor (transpiration).
succession The sequence of life forms
which follow each other on a -+ site be-
cause of gradual or far-reaching changes
of the site conditions in a -~ biotope. The
duration of succession is very dependent
on the type of -~ ecosystem. Aquatic eco-
systems are faster (one to several years)
than terrestrial ecosystems (sometimes
several thousand years).
secondary succession Resettlement of
abandoned agricultural land or clearings.
Such areas can produce a climax plant
community again in 100-200 years. (The
forests in the northern states of New Eng-
land are an example.) In Central Europe,
secondary succession and ecological bal-
ance are currently being considerably dis-
rupted by -> acid fog and acid rain and
-> forest damage,
sulfur dioxide (S02) A colorless, non-
flammable gas with an acrid smell which
can arise from the combustion of fossil fu-
els (coal, oil, gas). In the atmosphere it
changes to sulfuric acid and is thus the
main cause of -+ acid fog or acid rain. In
the Federal Republic of Germany every
year about 3 million tons of SO2 are re-
leased to the atmosphere, mainly from
large furnaces. This represents a quantity
of about 50 kg per person.
sulfuric acid (H2S04) A clear, colorless
and odorless, oily, hydroscopic liquid, and
a strong and important inorganic -> acid.
Sulfuric acid is used in the production of
fertilizers, dyes, detergents, and also for
medicaments, plastics, etc. Sulfate is the
primary acid anion responsible for the
leaching of cations and is formed when
sulfuric acid reacts with the soil solution.
symbiosis The long term living together
of different organisms to their mutual ben-
efit. The symbiotic partners may be differ-
ent species of plants, or animals in symbi-
osis with plants. -» Mycorrhiza is an ex-
ample of a symbiotic association between
a plant and a fungi.
synergistic effects In -»¦ forest damage
often symptoms occur that cannot be ex-
plained as being due to a single airborne
pollutant. If different pollutants act together
in such a way that the total effect is much
greater than the mathematical sum of the
individual damaging components, the ef-
fect is called synergistic.
TA-Luft The German abbreviation for the
Technical Directions for maintaining the
quality of the air. An administrative issu-
ance deriving from the -* Federal German
Deposition Protection Law of 1974 (in ef-
fect since 1984 in revised form). The TA-
Luft provides precise definitions, regulates
licensing procedures, sets limits for per-
missible -> immissions and -<¦ emissions
and determines measurement methods,
number of measuring points, and measur-
ing frequency, as well as determines the
heights of chimneys and gives instruc-
tions for ongoing control.
toxicity An estimate of how poisonous a
substance is. It may be acute (symptoms
after one dose), subchronic (symptoms af-
ter repeated doses within a short period)
or chronic (symptoms after repeated
doses over a longer period).
uneven-aged forest A forest built up in
stages in which trees of all age groups
grow in close proximity. The trunks are
harvested singly and not by clearcutting
larger areas as with normal lumbering. In
the gaps, trees of medium or low height
then grow, or -> natural regeneration
takes place. Uneven-aged forests are con-
sidered ecologically optimally stable and
are naturally managed forests (-> natural
forestry). They would be found anywhere
where disturbance has not occurred.
valuation A measure of the yield of wood
from a forest. II is calculated from the aver-
age height of the trees and the age of the
forest and graded in various classes.
willow (Salix) Widespread species are
silver willow, crack willow, basket willow
and purple willow. Willows are found often
in -» riparian habitats by the edge of
streams and river meadows. In Europe,
goat willow and auricled willow are a wide-
ly distributed timber species (-» pioneer
species).
yellow poplar (Liriodendron tulipi/era) The
twigs and branches of this tree are very
susceptible to breakage because of wind,
which is surely a reason why in Ihe moun-
tains it is mostly found in rich, sheltered
hollows. In the coves and on better soils it
grows up to 60 m in height, and plays an
important role, without ever dominating,
under natural conditions.
yew (Taxus baccata) The common yew
native to Europe, the Orient and North
Africa is an evergreen conifer that grows
extremely slow and is very shade tolerant.
It grows to only 10-15 m, but can reach an
age of up to a thousand years. Today the
yew is sparsely distributed, being found
mostly on steep slopes (yew forest
slopes). Its bark is frequently damaged
when young by game, so that if not pro-
tected by fencing, few individuals exceed
knee-height. The yew is therefore threat-
ened by extinction; in the Federal Repub-
lic of Germany it is a protected species.
Sources
Umwelt-Lexikon, Katalyse-Umweltgruppe
(Hrsg.), Kiepenheuer & Witsch, Koln, 1985.
Wie funktioniert das? Die Umwelt des
Menschen. Alheim, K.H. (Hrsg.), Bibliogra-
phisches Institut, Mannheim, 1981.
Meister, G., Schutze, Chr. und Sperber,
G., Die Lage des Waldes, GEO, Hamburg
1984.
Brockhaus Enzyklopadie, Brockhaus,
Wiesbaden, 1973.
Mc Graw-Hill Encyclopedia of Science &
Technology, Mc Graw-Hill, New York
1982.
Natural regeneration of spruce and rotting tree stump in the back. The dead ma-
terial is decomposed to minerals by detrivores providing nutrients for the suc-
ceeding generation.
-------
Index
A
acid fog 56, 65, 84, 92, 128
acid input 46
acid rain 27-28,114,128
acidification pulses 46-47
acids 128
adelgid, wooly 110
Adirondacks 13,124-125
adventitious shoot 80, 90, 93, 95,
128
airborne pollutants, annual
emissions of 24-25
nitrogen oxide 24-25
organic compounds 24-25
particles 24-25
sulfur dioxide 24-25
air pollution control (TA-Luft) 33-35,
135
alder 128
Alps 10-11,82-87
amelioration 128
annual emissions of air pollutants
24,25
annual ring analysis 45
annual rings 128
ash 128
aspen 128
assimilates 17
association of plants 128
atmospheric pollutants 26-29
B
bark beetle infestation 74
basswood 131
Bavarian Forest 10, 70-77
beech 128
biotope 18, 128
biozoonosis 129
birch 129
Black Forest 11, 88-97
buffering capacity 26, 129
c
carnivores 17-18
cause-effect research 36-115
cherry 129
chlorophyll 17
chlorosis 52, 66-67, 69, 72, 84, 90,
129
Clean Air Act 35, 129
climate stress 121
climate chamber 40
climate, local
Alps 82
Bavarian Forest 70
Black Forest 88
Eggegebirge 48
Fichtelgebirge 64
Harz 58
Hils 48
Munich Gravel Plain 78
Northern Appalachians 98
Soiling 42
Southern Appalachians 106
climate regulation 24
climax 25
compensation mechanism 116
complex high elevation disease
73-75, 122
concluding discussion 15
consumers 16-18
cuticule 129
D
damage catagory 30
damage symptoms, comparison of
116-119
decline symptoms, photos of typical
balsam fir 101,105
European beech 117
Fraserfir 107, 109, 111
Norway spruce 30, 51, 57, 63, 67,
69, 73,85, 87,93,95, 117-118,
124
Silver fir 31, 77, 91, 95, 117-118,
125
red spruce 101-102, 105, 107, 125
white birch 101
decomposer 16-18, 23
denitrogenation of flue gas 129
deposition 26, 129
wet 26
dry 26, 114-115, 129
desulfurization of flue gas 129
detritus feeders 17
detrivores 18, 129
dogwood 129
Douglas fir 129
drought 76
E
earthworms 129
ecological niche 129
ecology 130
ecosystem 16-22
changes 44-47
research 126-127
Eggegebirge 9, 48-49, 56-57
Electrical Power Research Institute
37
elm 130
emission 26, 130
Environmental Protection Agency
(EPA) 35-36
enzymes 130
equilibrium, ecological 25
erosion 33, 130
protection 24
excess nitrogen deposition 123-124
exchange capacity 92, 130
excursion
participants 7
to American forest decline study
regions 12-15
to German forest decline study
regions 8-11
F
fertilization 66-68, 92
fertilizer 130
Fichtelgebirge 10, 64-69
filter effect 24-26, 29
fir 130
flow injector analyzer 41
food pyramid 18
forestation, current
Alps 82
Bavarian Forest 70-71
Black Forest 88
Fichtelgebirge 64-65
Harz 58
Munich Gravel Plain 78
Northern Appalachians 98-99
Soiling 42
Southern Appalachians 106-107
forest benefits 24-25
forest communities 22-23
Appalachian forests 22-23
beech forests 22
horse chestnut and sugar maple
forests 23
montane forests 22
natural 22-23
oak forests 22
riparian forests 22
135
-------
spruce forests 22
yellow poplar forests 23
forest damage 130
forest decline 6, 130
Alps 82-83
Bavarian Forest 70-71
Black Forest 88-89
Fichtelgebirge 64-65
Harz 58-60
Munich Gravel Plain 78-79
Northern Appalachians 99
Soiling 42
Southern Appalachians 107
Weser Mountains 48-49
forest decline
distribution of 118
Federal Republic of Germany 28,
30-32
United States of America 32-33
forest ecosystem 16-26
stability of 25-26
forestry, natural 132
forest, uneven-aged 71, 77, 130
frost
damage 100, 102, 104, 119, 125
shock 73, 76, 80
fungi 23
G
game damage 130
general stress hypothesis 123
German-American cooperation
126-127
Green Mountains 12-13,100-103
growth 130
abnormal 117,119
reduction 53, 72, 84, 104, 108,
112-113, 116, 119
H
habitat 25
hardwood 22,130
Harz 9, 58-63
heavy metal deposition 109
heavy metals 29, 130
hemlock 130
herbaceous layer 130-131
herbivores 17-18
high output furnace regulations 130
Hils 9. 48-55
hornbeam 130
human intervention 23
humus 18, 131
hypotheses to explain forest decline
120-125
aluminum toxicity 120-121
complex-high-elevation disease
122-123
excess nitrogen deposition
123-124
general stress 123
organic air pollutants 124
red-needle disease 122-123
soil-acidification 120-121
hypotheses, working
Alps 86
Bavarian Forest 73-75
Fichtelgebirge 69
Harz 63
Hils 54-55
Munich Gravel Plain 81
Northern Appalachians 102
Soiling 44-45
Southern Appalachians 110,
113-114
I
Ice Ages 16
Immission Protection Law 131
International Biological Research
Program 9
ion budget study 60-63
L
land use, past
Alps 82
Bavarian Forest 71
Black Forest 88-89
Eggegebirge 48
Fichtelgebirge 64
Harz 58-59
Hils 48
Munich Gravel Plain 78
Soiling 42
Southern Appalachians 107
larch 131
leaching 26, 29
of magnesium 56-57
lichen 130-131
light-lover 131
linden 131
litter
reduced decomposition 45
utilization 131
long-range transport 26
M
magnesium deficiency 57, 60, 66,
69, 72-75
magnesium supply 67
magnolia 131
maple 131
measures taken in
Federal Republic of Germany
33-35
United States of America 35
metabolism 17, 20
mineralizers 17-18
mineral soil 18
mortality 102, 109
mosses 132
Mount Mitchell 13-14,108-111
mountain ash 132
Munich Gravel Plain 10, 78-81
mycorrhizae 108-110, 132
N
National Acid Precipitation
Assessment Program 36
National Science Foundation 36
necrosis 66, 132
needle cast fungus 72, 81, 87
needle damage 116-119, 121-125
Alps 84-87
Bavarian Forest 72-73
Black Forest 90, 93-97
Eggegebirge 57
Fichtelgebirge 66 69
Harz 60-63
Hils 51-54
Munich Gravel Plain 80-81
Northern Appalachians 100, 104
Southern Appalachians 108-110
needle loss 60, 62-63, 72, 87, 90,
93-96, 104, 108-109, 116
nitric acid 132
nitrogen
input 46
oxide 24-29, 132
saturation 45
Northern Appalachians 98-105
nutrient 17
cycle 16-17
deficiency 72, 76,84-85
nutrient supply
Alps 84-87
Bavarian Forest 72-75
Black Forest 92, 94
Fichtelgebirge 66-68
Harz 62-63
Munich Gravel Plain 80-81
Northern Appalachians 103
o
Oak Ridge National Laboratory 15,
112-115
oak 132
open-top chamber 9, 39, 56-57
organic compounds 24-25, 29,
124-125
ozone 9, 29, 132
effects 56-57, 73,122
exposure 56
stress 84, 92
P
particles, emission of 24-25
peroxyacetylnitrate (PAN) 29
pesticides 132
pH value 132
photooxidants 26, 29, 132
photosynthesis 17-18, 20, 38, 132
phytohormones 132
phytotoxic pollutants 27, 29
136
-------
pine 132
pioneer species 16, 133
pioneer system 25
pollutants, deposition of
Alps 84
Bavarian Forest 72-73
Black Forest 90-91, 94
Eggegebirge 56-57
Fichtelgebirge 68-69
Munich Gravel Plain 80-81
Northern Appalachians 102
Soiling 44-46
Southern Appalachians 109-110
pollution levels, exposure to
different 50-55
pollution monitoring network 56
poplar 133
ppb133
ppm 133
preventive care 35
producers 16-18
R
raw material 25
recreation area 25
red needle disease 81, 122-123
reducers 17
regeneration 132-133
regional research centers 38-115
regulations 33-35
research activities
Alps 84
Bavarian Forest 72, 76
Black Forest 90, 94
Eggegebirge 56
Fichtelgebirge 66
Harz 60-62
Hi Is 50-52
Munich Gravel Plain 80
Northern Appalachians 101, 104
Soiling 44-45
Southern Appalachians 108-110
Oak Ridge National Laboratory
112-113
research sites, characteristics of
Camels Hump
(Northern Appalachians) 100
Elendalm (Alps) 84
Freudenstadt (Black Forest) 93
Hils area 52-53
Hohenkirchner Forst
(Munich Gravel Plain) 80
Kalbelescheuer (Black Forest) 90
Lange Bramke (Harz) 60
Luchsplatzl (Bavarian Forest) 72
Mount Mitchell
(Southern Appalachians) 108
Oberwarmensteinach
(Fichtelgebirge) 66
Preul3ischer Velmerstot
(Eggegebirge) 56
RoBberg (Black Forest) 95
Selb (Fichtelgebirge) 66
State Forest (Soiling) 44
Steinhuttel (Bavarian Forest) 76
Walker Branch Watershed (Tenn.)
114
Whiteface Mountain
(Adirondacks) 104
Wulfersreuth (Fichtelgebirge) 66
rhizosphere 133
rhododendron 133
robinia 133
root analysis 45
root damage 41, 117, 121-123
Bavarian Forest 76
Hils 52-55
Soiling 42
Southern Appalachians 108-110
root fungus 80-81
s
scientific excursions 6-15
seed year 133
shade-lover 133
site 133
Smoky Mountains 15
snow breakage 32, 67, 72, 133
softwood 22
soil acidification 45, 47, 52-55,
62-63, 133
soil acidification hypothesis 9, 47,
120-121
soil pH value
Alps 86
Bavarian Forest 75
Black Forest 94, 97
Munich Gravel Plain 81
Soiling 44
Northern Appalachians 103
soil profile
Alps 84
Camels Hump 103
Fichtelgebirge 68
Northern Black Forest 97
Southern Black Forest 92
soil types
Alps 82-83
Bavarian Forest 71
Black Forest 89
Eggegebirge 49
Fichtelgebirge 65
Harz 58
Hils 48-50
Munich Gravel Plain 79
Soiling 42
Soiling 9, 42-47
Southern Appalachians 106-115
species, affected 118
spruce 133
window 117
stand management 134
State Institute for Air Pollution
Research (LIS) 8-9, 56-57
stomata, 17, 38, 134
storck's nest crown 31, 76-77, 95,
117
storm damage 32
stress factor
accompanying 55
inciting 54-55, 121
predisposing 54-55, 121
sub-top-dying 94
succession 25,134
sulfur dioxide 24-29,134
sulfuric acid 27, 134
sulfur input 46
surface water 62
symbiosis 134
synergistic effects 134
T
TA-Luft 33-35, 134
thinning 31, 66, 72, 76-77, 80, 119
throughfall 37, 62, 94
toxicity 134
trace metal accumulation 112-113
transmission 26
transpiration rate measurements 38
tree physiology research 126
tree ring analysis 100,128
tree species, relative areas of
Alps 82
Bavarian Forest 70
Black Forest 88
Fichtelgebirqe 64
Harz 58
Munich Gravel Plain 78
Soiling 42
Weser Mountains 48
u-z
uneven-aged forest 134
valuation 134
water
filter 24
flow 24,61-62
wet deposition 62
willow 134
wind protection 25
yellowing 57, 62-63, 67, 84, 90, 93,
95, 118-119, 124-125
yellow poplar 134
yew 134
137
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