United States
Environmental Protection
Agency
Environmental Research
Laboratory
Corvallis OR 97333
EPA/600/3-86/033
July 1986
Research and Development
vvEPA
Ecoregions of the
Pacific Northwest
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EPA/600/3-86/033
July 1986
ECOREGIONS OF THE PACIFIC NORTHWEST
by
James M. Omernik
Environmental Research Laboratory -- Corvallis
U.S. Environmental Protection Agency
200 S.W. 35th Street
Corvallis, Oregon 97333
and
Alisa L. Gallant
Northrop Services, Inc.
1600 S.W. Western Boulevard
Corvallis, Oregon 97333
0.'?, Environmental Protection Agency
-n &, Library (5PL-16)
'--» S. Dc-arborn Street, Boom 1670
Ciucago, -Ii 60604
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DISCLAIMER
The information in this document has been funded wholly by the United
States Environmental Protection Agency. It has been subjected to the Agency's
peer and administrative review, and it has been approved for publication as an
EPA document. Mention of trade names or commercial products does not consti-
tute endorsement or recommendation for use.
11
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ABSTRACT
A map of ecoregions of the Pacific Northwest has been compiled to assist
managers of aquatic and terrestrial resources to better understand the regional
patterns of the realistically attainable quality of these resources. The
ecoregions are based on perceived patterns of a combination of causal and
integrative factors including land use, land surface form, potential natural
vegetation, and soils. Descriptions and photographs are included to provide a
synopsis of the more significant characteristics affecting and distinguishing
each ecoregion. A synoptic approach similar to that used to define these
ecoregions is also useful for applications of the map. Initial efforts to use
the framework are at the state level of management and center on identifying
attainable ranges in chemical quality, biotic assemblages, and lake trophic
condition.
111
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PHOTOS
Number Page
1 Coast Range Ecoregion, aerial photograph at 5,000 feet 11
2 Coast Range Ecoregion, aerial photograph at 2,000 feet 12
3 Coast Range Ecoregion, ground photograph 12
4 Puget Lowland Ecoregion, aerial photograph at 5,000 feet 14
5 Puget Lowland Ecoregion, aerial photograph at 2,000 feet 15
6 Puget Lowland Ecoregion, ground photograph 15
7 Willamette Valley Ecoregion, aerial photograph at 5,000 feet .... 16
8 Willamette Valley Ecoregion, aerial photograph at 2,000 feet .... 17
9 Willamette Valley Ecoregion, ground photograph 17
10 Cascades Ecoregion, aerial photograph at 5,000 feet 19
11 Cascades Ecoregion, aerial photograph at 2,000 feet 20
12 Cascades Ecoregion, ground photograph 20
13 Sierra Nevada Ecoregion, aerial photograph at 5,000 feet 21
14 Sierra Nevada Ecoregion, aerial photograph at 2,000 feet 22
15 Sierra Nevada Ecoregion, ground photograph 22
16 Eastern Cascades Slopes and Foothills Ecoregion, aerial photograph
at 5,000 feet 24
17 Eastern Cascades Slopes and Foothills Ecoregion, aerial photograph
at 2,000 feet 25
18 Eastern Cascades Slopes and Foothills Ecoregion, ground photograph . 25
19 Columbia Basin Ecoregion, aerial photograph at 5,000 feet 26
20 Columbia Basin Ecoregion, aerial photograph at 2,000 feet 27
21 Columbia Basin Ecoregion, ground photograph 27
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22 Northern Rockies Ecoregion, aerial photograph at 5,000 feet .... 28
23 Northern Rockies Ecoregion, aerial photograph at 2,000 feet .... 29
24 Northern Rockies Ecoregion, ground photograph 29
25 Blue Mountains Ecoregion, aerial photograph at 5,000 feet 31
26 Blue Mountains Ecoregion, aerial photograph at 2,000 feet 32
27 Blue Mountains Ecoregion, ground photograph 32
28 Snake River Basin/High Desert Ecoregion, aerial photograph at 5,000
feet 3
29 Snake River Basin/High Desert Ecoregion, aerial photograph at 2,000
feet 34
30 Snake River Basin/High Desert Ecoregion, ground photograph 34
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INTRODUCTION
Some of the most difficult and seemingly unanswerable problems plaguing
water resource managers center on "regional representativeness" of data and
study results, and "attainable" ecosystem conditions or quality. Spatial
applicability of site specific (or watershed specific) ecosystem quality
studies have long been a subject of controversy. Processes and relationships
that are apparent in one part of the country commonly do not appear the same in
other parts. Interrelationships between natural and anthropogenic factors
affecting ecosystem quality vary spatially and temporally in such a complex
fashion that mathematical models developed to predict land use/water quality
relationships are of questionable value at best when used outside the specific
area in which they were developed. These spatial and temporal interrelation-
ships are simply too complex to allow the development of effective quantitative
geographic predictive schemes until a qualitative understanding of the regional
patterns of the appropriate interrelationships or processes has been reached.
Ecoregions"'" of the United States have been mapped to alleviate these
problems and to provide a geographic framework for more efficient management of
aquatic ecosystems and their components. The ecoregion maps are intended to
help water resource managers better understand the regional patterns of eco-
system quality and the relative importance of factors that may be determining
this quality. Most important, this geographic framework can establish a
logical basis for characterizing ranges of ecosystem conditions or quality that
are realistically attainable. Realistically attainable quality is, of course,
relative to regional patterns of cultural as well as physical constraints. For
most of the conterminous United States, particularly regions of cultivated
cropland, it is unrealistic to expect an attainable surface water quality or a
quality of terrestrial conditions of the level possible before major human
settlement. What is realistically attainable is a quality possible given a set
of economically, culturally, and politically acceptable protective measures
that are compatible with regional patterns of natural and anthropogenic charac-
teri sties.
The ecoregion maps were compiled at two scales. A national map was
prepared at a scale of 1:7,500,000, and more detailed regional maps were
prepared at a scale of 1:2,500,000. The regional map of the Pacific Northwest
comprises the first of the larger scale maps and is the first in a series of
regional maps covering the conterminous United States. The maps provide
general information on the spatial extent and characteristics of each eco-
region .
"I" The term ecoregions was coined by J. M. Crowley (1967) and popularized by
Robert G. Bailey (1976) to define a mapped classification of ecosystem
regions of the United States. Unlike many coined words or words used to
express special new meanings, such as "landscape" or "stream order," there is
little disagreement, misunderstanding, or difference of opinion about the
meaning of "ecoregion." Ecoregions are generally considered to be regions of
relative homogeneity in ecological systems or in relationships between
organisms and their environments.
1
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BACKGROUND
Neither the concept of ecological regions nor the attempt to delineate
them is new. Water resource managers and scientists have commonly recognized
the existence of regions. However, most who have compiled similar type maps
have based the boundaries of their regions on a single geographic characteris-
tic such as physiographic division or vegetation type. Although these maps are
helpful in some areas of the country, their usefulness for resource management
varies from one place to another.
Part of the difficulty that has been encountered in defining ecological
regions probably lies in the perception of "region" and the common misconcep-
tion that, once ecological regions have been drawn, they will provide a power-
ful mechanism for making quantitative assessments about ecosystems and their
components. John Fraser Hart's definition of a "region" and its utility is
particularly appropriate to the definition and understanding of ecoregions.
Hart (1982) stated:
The concept of the region is not a powerful
technical tool, but it is merely a useful intellectual
device for organizing and presenting information. A
region is a more or less homogeneous area that differs
from other areas. To use a more contemporary jargon,
within region variance is less than between region
variance. The best regions are those that are based on
the greatest amount of interrelatedness.
Ecological regions that have been patterned after mapped information on a
single geographic characteristic such as physiography or vegetation are gener-
ally based on understandings of relationships and/or processes between these
characteristics and ecosystem components, and inductive logic that these
relationships and processes will reflect useful patterns of ecosystems.
Regional patterns of aquatic ecosystems and their components (physical habitat,
hydrology, water chemistry, and biotic assemblages) are related to a combina-
tion of characteristics (such as climate, soils, physiography, and vegetation);
moreover, the relative importance of each characteristic varies considerably
from one place to another. This applies regardless of the resolution of
regional definition; that is, whether one is dividing the United States into
the broadest of regions (say four to eight), or smaller regions of greater
homogeneity. Ecoregions at whatever scale of definition should not be based on
single characteristics, nor are there definite rules for defining them.
There are two notable examples of classification that have been used for
illustrating ecological regions and that have incorporated spatial patterns of
several factors in their design. The first is the Land Resources Regions and
Major Land Resource Areas of the United States (USDA Soil Conservation Service,
1981). Originally developed by Morris Austin (1965), this map has since
undergone two revisions. In general, Land Resource Regions and Major Land
Resource Areas are characterized by a particular combination of soils, climate,
water resources, vegetation type, and land uses. The classification was
designed by the USDA Soil Conservation Service, to aid in making decisions
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about national and regional agricultural concerns. The scales at which the map
units were drawn, and the bias toward agricultural applications, limit applic-
ability of the classification for defining ecoregions.
The second example is the map of Ecoregions of the United States (Bailey,
1976). In compiling this map, Bailey considered climate, potential natural
vegetation, soils, and land surface form. However, each hierarchical level of
classification of Bailey's ecoregions is based primarily on alignments from a
particular map. Ecoregion sections (the smallest units shown on Bailey's map)
were, for example, based on map units or groups of map units from Kuchler's map
of potential natural vegetation (Kuchler, 1970). Ecoregion divisions (two
steps up in size from the section level on Bailey's map) are, on the other
hand, based on climate (Trewartha, 1943).
Our approach for defining ecoregions grew out of an effort to classify
streams for more effective water quality management and was inspired by the
philosophies of Warren (1979) as well as Bailey (1976). Not wishing to
reinvent the wheel, in the initial stage of this work we used Bailey's eco-
region map as the spatial framework for examining aquatic ecosystems (Hughes
and Omernik, 1981a; Omernik et aK, 1982). While characterizing the typical-
ness of portions of these ecoregions, we developed what we believe to be a more
satisfactory scheme for defining aquatic ecoregions. Because the approach is
based on patterns of terrestrial characteristics, the regions are not exclusive
to aquatic ecosystems, but depict terrestrial ecosystems as well.
The second stage of our classification work, involving examination of
spatial patterns of stream quality data in several parts of the United States,
reaffirmed the need for an alternative to present schemes for regionalizing
water resource management. The USDA's Land Resource Regions were too coarse
and, for most parts of the country, Major Land Resource Areas were too small.
Bailey's ecoregions proved inadequate in most areas, primarily because of their
dependence on a single mapped characteristic (potential natural vegetation) at
the section level of classification. Although Hydrologic Units (U.S. Geolog-
ical Survey, 1982) should not be considered for illustrating ecological
regions, they have been used extensively as a geographical framework for water
resource management. We found the Hydrologic Units least helpful of any
available spatial classification, due mostly to the lack of correlation between
topographic drainage areas and the basic causal and integrative characteristics
that affect or help define regional patterns in aquatic ecosystem quality.
None of the available classifications afforded a means to evaluate the
typicalness of areas within ecoregions, within region variation, or relative
typical ness of entire watersheds. Such a mechanism is necessary for evaluating
existing data, for designing sampling schemes to address regional representa-
tiveness and for assessing regional patterns of attainable aquatic ecosystem
quality. Ecoregions are based on patterns of homogeneity in a combination of
geographic characteristics. Areas within an ecoregion that share all of the
characteristics predominant in the ecoregion are the most typical portions of
that ecoregion. The quality of ecosystems in the most typical areas should be
less variable than in the remainder of the ecoregion where most (but not all)
of these predominant characteristics exist.
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Our approach for defining aquatic ecoregions is based on the hypothesis
that ecosystems and their components display regional patterns that are
reflected in combinations of spatial characteristics that caused them to be
what they are. These causal characteristics include climate, mineral avail-
ability (soils and geology), vegetation, and physiography. Each of these
factors are more or less related to one another, and the level of interrelated-
ness varies spatially. We emphasize that the level to which these factors are
important in determining the character of aquatic ecosystems also varies
considerably from one place to another. Through analysis of a combination of
small-scale maps of some of the most important causal and integrative character-
istics (such as land use), distinct patterns of homogeneity in ecosystems can
be perceived.
MAP DEVELOPMENT
This approach for defining aquatic ecoregions was undertaken in several
steps (Omernik, submitted to the Annals of the Association of American Geo-
graphers, 1986). The initial step involved gathering small-scale maps of
factors that either cause regional variations in ecosystems, or tend to inte-
grate causal factors. The four small-scale maps found to be most useful were:
Land Use (Anderson, 1970); Land Surface Form (Hammond, 1970); Potential Natural
Vegetation (Kuchler, 1970); and soils [from varying sources; Simonson (1975)
and USDA Agricultural Experiment Station of the Wesern States Land-Grant
Universities and Colleges (1964) were used as component maps for the Pacific
Northwest].
The land use map provided a strong integrative tool for revealing eco-
system patterns in most of the United States because it reflects spatial
patterns in potentials and capacities of the land. The potential natural
vegetation (PNV) map was also a strong, integrative tool because it synthesizes
a variety of natural and imposed land features. Hammond's land surface form
map synthesizes regional patterns of slope, local relief, and profile types
(e.g., whether, and how much, of the more gently sloping land is located in the
lowlands or the uplands) into relatively homogeneous classes of land surface
form. The classification scheme of the soils taxonomy map (USDA Soil Conserva-
tion Service, 1970) was probably the most appropriate for our purposes, but
because of its inaccuracies [due largely to the poor data base and inappro-
priate cartographic techniques used in its compilation (Gersmehl, 1977)], we
relied on other small-scale regional soil maps.
Several other maps were consulted, generally to verify the regional
accuracy of each of the component maps and to further support the patterns that
indicated ecoregions. Those most helpful for this purpose were Surficial
Geology (Hunt, 1979), Physical Divisions (Fenneman, 1946), and Land Resource
Regions and Major Land Resource Areas of the United States (USDA Soil Conserva-
tion Service, 1981). Maps in Climates of the United States (Baldwin, 1973) and
the Census of Agriculture, Graphic Summary (U.S. Department of Commerce, Bureau
of Census, 1969, 1974, and 1978) were also used.
The second step in developing the ecoregion map was to analyze these maps
together to rough out regions that exhibited a relative amount of spatial
homogeneity in characteristics of soils, land use, land surface form, and
potential natural vegetation, and to tabulate the identifying classes of each
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(Table 1). Ecoregion size is a function of the relative spatial homogeneity in
an area, as compared to adjacent areas, at a scale useful for regionalizing
resource management. For our purposes, ecoregions should be large enough to
contain entire topographic watersheds of at least 200^ square miles, but not so
large as to encompass contrasting relatively homogeneous regions that, them-
selves, contain entire watersheds of at least 200 square miles. Some regions
exhibit a patchwork, or mosaic, of conditions that are common throughout the
region -- too patchy to allow individual ecoregions to be delineated at this
scale of analysis. The Blue Mountains Ecoregion, for example, is characterized
by contrasts as compared to some adjacent ecoregions. There, lower elevation
foothill areas consist of mostly sagebrush and grassland steppe widely used for
rangeland. The higher mountainous portions of the ecoregion support coniferous
forests, and timber harvest is a major land use. Nearly all watersheds of 200
square miles and greater in this ecoregion contain a mosaic of these character-
istics.
Subsequent steps in map development inlcuded delineating ecoregion bounda-
ries and defining the most typical portions of each ecoregion. The most
typical portions of each ecoregion are those areas sharing all of the charac-
teristics that typify that ecoregion. The remainder, or generally typical
portions of each ecoregion, share most, but not all of these same characteris-
tics.
The final step was to color-code each ecoregion to convey a sense of the
broader, multi-region patterns. Regions characerized by mostly cropland were
assigned shades of brown and regions characterized by forests were assigned
shades of green or blue. Grasslands were generally illustrated by shades of
yellow, and very arid areas, shades of pink or red. Portions of each aquatic
ecoregion are presented in darker color tones to denote the most typical areas
of the ecoregions. The lighter-toned portions of each ecoregion represent the
generally typical areas.
APPLICATIONS
The primary function of the ecoregion map is to provide a geo-
graphic framework for organizing aquatic ecosystem resource information. This
framework should allow managers, planners, and scientists to better: (1)
compare the similarities and differences of land/water relationships; (2)
establish water quality standards that are in tune with regional patterns of
tolerances and resiliences to human impacts; (3) locate monitoring, demonstra-
tion, or reference sites; (4) extrapolate from existing site specific studies;
and (5) predict the effects of changes in land use and pollution controls.
Applications will vary from one state and region to another, as do the issues
of concern such as nonpoint source pollution, eutrophication, and water with-
drawals. Resource management interests and priorities are understandably
different in the Coast Range, than they are in the Snake River Basin/High
Desert, than they are in the Northern Rockies, and so on. In spite of (or
The majority of references used in this research presented information in
English units of measure. We have presented our measurements accordingly.
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perhaps because of) these differences, there is a universal need to understand
the spatial patterns of realistically attainable conditions and quality of
aquatic ecosystems.
Initial efforts to use this ecoregion framework are underway in Ohio,
Colorado, Texas, Arkansas, Oregon, and Minnesota. These statewide projects
focus on aquatic systems, mainly attainable ranges of chemical quality and
biotic assemblages. The applications were designed in a synoptic fashion to
allow sampling efforts to be organized to: fit a regional structure for
analysis, comparison, and reporting; select representative sample sites; sample
an array of conditions to ascertain the variability within and between regions.
The specific steps required to structure this approach are typically as
follows:
1. Boundaries of ecoregions and their most typical portions were transferred
to state level (normally 1:500,000-scale) maps. The most typical portions
of ecoregions are generally those areas that share all^ of the characteris-
tics that are predominant in each ecoregion (Table IT. The remaining
portions, generally typical of each ecoregion, share most, but not all, of
these same characteristics.
2. Streams and watersheds were selected within the most typical portions of
each ecoregion in such a way to represent the least impacted conditions
and a realistic range of stream sizes. Streams were characterized by the
relative level of disturbance in the watersheds, size,''" and the extent to
which their watershed occupied a particular ecoregion and most typical
portion of that ecoregion. The key to this process was ensuring typical-
ness of each stream/watershed in terms of overall land surface form,
vegetation, soil, and land use characteristics as well as a relative lack
of human disturbance. For example, one would not expect to find a typical
stream draining 125 square miles in the Willamette Valley to be void of
cropland, or even with less than 75% cropland. However, there are streams
of that size in that ecoregion that drain watersheds having relative lack
of population density and industrial impact, relatively little stream
channelization, and a relative abundance of woody riparian vegetation.
3. Mapping and statistical analyses were performed to determine: (1) the
Tegional patterns of attainable quality of aquatic ecosystem characteris-
TTTcs of interest; (2) how these characteristics appear to be related to
Jtream/watershed size; (3) how these characteristics vary within arid
bFtween ecoregions; and (4) what regional properties appear to be most
TJeHpful for explaining these variations and enabling more precise predic-
tions of attainable quality.The latter (4) involves a synoptic sorting
technique, incorporating qualitative analyses of mapped characteristics in
The approximate area upgradient from a point on a stream is a more meaningful
measure of stream size than order, particularly for small scale (state,
regional, and national) analyses (Hughes and Omernik, 1981b; Hughes and
Omernik, 1983). Where variations in runoff are greater within or between
ecoregions, consideration of these variations must be included.
9
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the earlier stages. Then, as significant regional associations become
apparent, more detailed analyses leading to more quantitative methods
become appropriate.
Where lakes rather than streams are the concern, similar methods apply.
In the state of Minnesota, for example, water resource managers are attempting
to develop a better capability for predicting attainable nutrient levels and
eutrophication in lakes on a regional basis. Although the design is not
complete, a summary of the initial concept is to:
1. Sort available lake data on nutrient levels and trophic state by eco-
region.
2. Classify the lakes within each ecoregion by as few characteristics as
possible to include depth, clarity, and size.
3. Categorize each lake by its relative amount of human disturbance, both
point (e.g., sewage treatment plant) and diffuse or nonpoint (e.g., septic
tanks in close proximity to lake shore).
4. Map color-coded values for certain classes of lakes (e.g., shallow, clear,
small lakes) to enable comparison with spatial patterns of factors that
may help explain variations in value. These factors include surface
configuration (e.g., moraine vs. outwash plain), vegetation type (e.g.,
extent of coniferous, deciduous, or mixed forest in the watershed), and
bedrock type.
ECOREGION DESCRIPTIONS
The ecoregion descriptions are presented here to provide a general
synopsis of the more significant characteristics that affect aquatic ecosystems
and their major components. In short, the descriptions provide an amplifica-
tion of the combination of characteristics listed in Table 1. Each description
presents a brief summary of regional landscape features, such as landforms and
local and general topographic relief, followed by information related to
ecoregion stream and watershed drainage characteristics. Subsequent paragraphs
outline major vegetation types, major soil taxa, and predominant land uses. A
final section lists significant disturbance types contributing to stream
quality degradation. The descriptions pertain only to the area within the
regional map of the Pacific Northwest."''
The accompanying photos have been taken in the most typical portion of
each ecoregion and illustrate typical characteristics rather than extremes or
anomalies. The high oblique photos have been taken at approximately 5,000 feet
above mean terrain and illustrate general characteristics of the ecoregion.
The low oblique aerial photos (taken about 2,000 feet above the streams) and
ground photos are of characteristic, relatively undisturbed streams and their
riparian zones.
Descriptions have not been provided for ecoregions having only a small
portion of their total area represented or having only "generally typical"
area represented in the three-state area of the Pacific Northwest.
10
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Information included in the ecoregion descriptions has been obtained from
a variety of sources (Archie, 1981; Anderson, 1970; Crouse and Kindschy, 1981;
Franklin and Dyrness, 1973; Hammond, 1970; Hubbard et aK, 1982; Irwin and
Hotz, 1981; Kuchler, 1970; NOAA, 1974, 1984; Rickert et cH ., 1978; Simonson,
1975; Snavely, 1981; Tabor, 1981; USDA Agricultural Experiment Stations of the
Western Land-Grant Universities and Colleges, 1964; USDA Soil Conservation
Service, 1981; USDA Forest Service, 1970; Weeks, 1970). Two sources that have
proven particularly helpful and were heavily relied upon in the production of
this text are: Natural Vegetation of Oregon and Washington (Franklin and
Dyrness, 1973), and Land Resource Regions and Major Land Resource Areas of the
United States (USDA Soil Conservation Service, 1981). Information pertaining
to stream miles was determined by extrapolating from regionally representative
7.5 and 15-minute topographic maps. Estimates of watershed sizes necessary to
support perennial stream flow were interpolated from USGS Water Resources Data
and 1:250,000-scale topographic maps.
Coast Range
This ecoregion includes the Pacific Coast Range and coastal valleys and
terraces (Photos 1-3). Much of the region is highly dissected by perennial
streams, commonly having two to three miles of streams per square mile. Local
relief is between 1,500 to 2,000 feet, with mountain tops generally below 4,000
feet. The combination of maritime weather systems and high local topographic
relief results in large differences in local precipitation. Thus, average
annual precipitation ranges from 55-125 inches and is heaviest in the winter
months and lightest in the summer. Perennial streamflow is maintained in
watersheds draining areas of less than one square mile; however, larger streams
in this ecoregion drain greater than 300 square miles. The ecoregion is approx-
Photo 1, Highly productive, dense Douglas-fir forests, patch clearcuts, and average annual pre-
cipitation of 55-125 inches are typical of the Coast Range Ecoregion.
11
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Photo 2.
Photos 2 and 3. Clear, high gradient streams with
high runoff per unit area are common in the Coast
Range Ecoregion. Average annual runoff in the Siletz
River is over 100 inches.
PhotoS.
12
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imately 18,000 square miles in size. Due to the geomorphic character of the
ecoregion, there are relatively few lakes, generally occurring where coastal
dunes impound streams.
The Coast Range Ecoregion is densely forested with Douglas-fir, western
hemlock, Sitka spruce, and western red-cedar. Lodgepole pine is common along
coastal dunes. In the southern portion of the ecoregion, tree species also
include Port-Orford cedar, California bay laurel, madrone, tanoak, and golden
chinquapin. Forest understories are continuous mats of shrub and herbaceous
vegetation. Common shrubs include: salmonberry, rhododendron, willow, vine
maple, and evergreen huckleberry. Grasslands, occurring on headlands, repre-
sent a small percentage of the region.
Soils are developed mainly from sandstone, siltstone, shale, and basalt
rock sources, and exhibit a wide range of characteristics. Haplohumults, on
mountain slopes, foothills, and terraces, and Dystrandepts, Dystrochepts,
Dystropepts, and Haplumbrepts, on mountain slopes, foothills, coastal plains,
and terraces are the most common soils in the region. Tropaquents form in
coastal lowlands and valleys. Tropopsamments and Troporthods are formed on
sand dunes and terraces.
The wood products industry is the mainstay of the ecoregion; harvesting of
timber has occurred extensively throughout the coastal mountains. Cultivation
of forage and grain for dairy cattle occurs locally in larger valleys and along
the coast. A small percentage of cleared land is cultivated for vegetables and
fruit. Urban development is concentrated on land bordering water, particularly
ocean embayments.
Moderate to severe hillslope and stream bank erosion, resulting from
removal of vegetation by logging, road construction, overgrazing, or cultiva-
tion is common in many parts of the Coast Range. Road construction for timber
removal contributes to landslides and hillslope slumping. Large woody debris
in headwater reaches may be transported downstream during major hydro!ogic
events, causing scouring and increasing stream sedimentation, which in turn can
lead to loss of habitat for stream biota. Some streams are chemically affected
by industrial byproducts from paper and pulp mills, urban development along and
bordering water, and easy accessibility of stream channels to livestock.
Puget Lowland
The Puget Lowland Ecoregion includes the open hills and tablelands of
glacial and lacustrine deposits in the Puget Sound Valley (Photos 4-6). The
ecoregion is bordered by the Coast Range Ecoregion to the west, the Cascades
Ecoregion to the east, and the flatter Willamette Valley Ecoregion to the
south. The northern portion of the Puget Lowland ecoregion consists of low
elevation (sea level to 500 feet) flats surrounding the Puget Sound area
interspersed with high hills, approaching 2,000 feet in elevation. The south-
ern and peripheral portions of the ecoregion contain a greater concentration of
hills and low mountains, with peaks often exceeding 2,500 feet. Local relief
in the more rugged portions varies from 800 to 1,000 feet. Due to the rain-
shadow effect of the mountains bordering the ecoregion to the west, average
annual precipitation is generally 35 to 50 inches. Stream density is typically
on the order of one to two miles of streams per square mile. Most streams
13
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draining the 9,000 square miles comprising the ecoregion are perennial. The
larger inclusive watersheds average 140 square miles, with permanent stream
flow emanating from drainages as small as two square miles. Numerous small
lakes dot the landscape.
Most of the land is forested and Douglas-fir is a major subclimax timber
species. Stands of lodgepole pine, western white pine, and ponderosa pine are
common forest constituents with Douglas-fir. Local vegetation communities
differing from the major forest vegetation are related to local variations in
climate and soil type; examples are prairie, oak woodland, northwestern paper
birch, quaking aspen, Rocky Mountain juniper, and swamp and bog communities.
The majority of the soils in the northern portion of the ecoregion are
formed from glacial materials under the influence of coniferous forest vegeta-
tion. The most common soils are Haplorthods, often associated with Xerumbrepts,
Haplaquepts, Xeropsamments, and Haploxerolls. Well drained Haplohumults and
poorly drained Haplaquepts are most common under forest vegetation in the
southern portion of the ecoregion and are derived from upland basic igneous or
sedimentary parent materials. Argixerolls, developed under grassland vegeta-
tion, are also common in this portion of the ecoregion, particularly on terrace
land forms.
Timber harvest is an important land use in the ecoregion. Cleared areas
support crops of grains, wheat, vegetables, and occasional irrigated cash
crops. Urban development is concentrated along stream and coastal stretches.
Municipal wastes and industrial wastes from smelters, related metallurgical
industries, and pulp and paper mills are among the major point sources of
pollutants affecting water quality in Puget Sound and many streams in the
ecoregion. Water quality is also affected by erosion resulting from road
construction and timber harvest. Urbanization along the Sound and its tribu-
taries imposes direct human impact on water quality through seepage from
Photo 4. The numerous
small lakes and hummocky
and hilly appearance of
the Puget Lowland
Ecoregion attest to
several epochs of glacial
deposits. Timber harvest
is an important land use
in this region.
14
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Photos 5 and 6. Streams in the Puget Lowland
Ecoregion normally support corridors of dense
riparian vegetation. Some streams are impacted
from seepage through septic systems and altera-
tion of stream banks and stream-side forest.
Photos.
Photo 6.
15
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individual septic systems and alteration of stream banks and streamside forest.
An overall reduction in cropland to accommodate growing urbanization suggests a
shift in land use emphasis which may further alter water quality through
increased demands on existing wastewater treatment facilities.
Willamette Valley
The majority of this ecoregion comprises the valley floor of the
Willamette River in Oregon and consists of nearly level to generally sloping
floodplains bordered by higher terraces (Photos 7-9). The northern portion of
the ecoregion extends into Washington, approximately to the Lewis River. The
southern portion extends just south of the South Umpqua River. The periphery
of the ecoregion includes foothills grading into the Coast Range Ecoregion in
the west and Cascades Ecoregion in the east. Elevation of the valley floor
varies from 100 to 300 feet, and local changes in relief are gradual. Eleva-
tion of the foothills surrounding the valley increases from 1,000 feet in the
northern portion of the ecoregion to greater than 2,000 feet in the central and
southern portions. Annual precipitation averages 40 inches, with the northern
portion of the valley receiving more moisture than the southern portion.
Whereas the majority of streams draining the northern portion of the
ecoregion are perennial, most streams draining the southern portion are inter-
mittent. Nearly all of the larger perennial streams originate in the more
mountainous ecoregions adjacent to the Willamette Valley Ecoregion. The
largest streams having watersheds contained entirely within the ecoregion
commonly drain less than 100 square miles. The relatively few natural lakes in
this ecoregion are mainly river meander scars. Numerous small impoundments
exist for log ponds, irrigation, and livestock.
Photo 7. Most of the Willamette Valley Ecoregion is in cropland. Due to the normal summer
drought, irrigation is extensive.
16
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PhotoS.
Photos 8 and 9. Streams in the Willamette Valley are
generally low gradient and meandering. Flooding is
common in the winter months.
Photo 9.
17
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The natural forest vegetation of the Willamette Valley Ecoregion is
represented by Oregon oakwoods (Oregon white oak interspersed with Douglas-fir,
grand fir, and bigleaf maple) and mixed stands of cedar, hemlock, and Douglas-
fir. Cottonwood, willow, and alder are dominant riparian genera. Though
presently limited in area! extent, prairie vegetation consists of fescue,
brome, and sedge.
The principal soils of the valley floor are Argixerolls, with lesser
amounts of HaploxerolIs, Haplaquolls, and Albaqualfs. They are derived primar-
ily from alluvial and lacustrine deposits developed under grassland vegetation.
Poor drainage is a common soil feature and drainage tiles assist in removing
excess water from croplands. Along the adjacent uplands and low hills of the
valley, soils are largely Haplohumults with some Xerumbrepts, Haploxeralfs, and
Argixerolls. The upland soils are derived from igneous and sedimentary parent
materials.
The ecoregion is typified by an agricultural mosaic of grains, seed crops,
fruit, mint, berries, and vegetables. Cropland areas, interrupted by pasture,
woodland, and forest have essentially replaced prairies, wetlands, and many
wooded areas in this ecoregion. Subsequent expansion of urbanization and
industry have resulted in the reduction of cropland, woodland, and forest land.
Stream quality is affected in a variety of ways as a result of agricul-
tural practices, particularly irrigation. Extensive stream channelization,
particularly in the southern half of the ecoregion, has reduced the number of
stream miles and greatly altered the natural character of the riparian habitat.
Numerous impoundments along streams facilitate water withdrawal needs through-
out the summer drought season, causing a reduction in stream flow. This can
result in elevated water temperatures, increased growth of aquatic vegetation,
and barriers to fish migration, reducing the quality and quantity of habitat
for stream biota. Runoff carries fertilizer and pesticide compounds to
streams. Erosion of topsoil contributes to stream turbidity and necessitates
increased use of soil amendments. Accessibility of stream channels to overuse
by livestock promotes stream bank erosion and instream manure deposits.
Urban growth in the valley has increased the demand for water, the load on
existing water and sewage treatment plants, and the number of point source
contributors of water pollutants. Byproducts from pulp and paper mills and
metallurgical industries are major point source contributors of pollutants into
the Willamette River and its larger tributaries.
Cascades
The Cascades Ecoregion is comprised of the Cascades Mountain Range in
Oregon and Washington and the Olympic Mountains' of the Olympic Peninsula in
Washington (Photos 10-12). The Cascades Range consists of two distinct physio-
graphic divisions: the High Cascades, or eastern portion of the range, and the
geologically older, more dissected western portion of the range. The 28,000
square miles comprising the ecoregion are characterized by high mountains and
deeply dissected valleys. Elevations range from near sea level at the Columbia
River to greater than 10,000 feet in the peaks of the High Cascades. Most of
the ecoregion is between 2,000 and 7,000 feet in elevation, and local relief
often exceeds 3,000 feet. Average annual precipitation varies across the
ecoregion from 50 to 100 inches.
y 18
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Stream density is commonly one and a half to two miles of perennial
streams per square mile. Watersheds as small as one to two square miles
support perennial streams, and larger watersheds that are contained completely
within the ecoregion commonly exceed 500 square miles. Numerous natural lakes
are scattered along the crest of the Cascades, resulting from glacial geo-
morphic processes. Man-made reservoirs are common at lower elevations in the
ecoregion.
Most of the area is
fir, noble fir, Pacific
hemlock and western red-
subalpine fir, whitebark
Forest understories are
towards sparse in the Hi
of shrubs such as: vine
berry, Oregon grape, and
flower and a variety of
grass, fescue, bluegrass
densely forested. Typical tree species are: Douglas-
silver fir, and western white pine, with western
cedar providing climax forest cover. Mountain hemlock,
pine, and Englemann spruce grow at higher elevations.
dense in the western portion of the ecoregion, grading
gh Cascades. Forest understories are commonly composed
maple, rhododendron, oceanspray, huckleberry, black-
sal al. Forest floors are often matted with twin
herbaceous species. Alpine meadows consist of bent-
and sedge.
Soils of the Cascades Ecoregion
are developed from pyroclastic
materials such as breccias and tuffs
and basic igneous rock types, mainly
pumice, andesite, and basalt.
Dystrandepts, Haplumbrepts,
Vitrandepts, Xerumbrepts, Cryorthods,
Haplorthods, and Haploxerults devel-
oped from pyroclastic parent mater-
ials. Argixerolls, Haplohumults,
Haplumbrepts, and Xerumbrepts devel-
oped from igneous materials. Glacial
deposits are abundant throughout the
ecoregion; soils on glacial till are
Cryandepts, Vitrandepts, Xerochrepts,
Cryumbrepts, Haplumbrepts, Cryor-
thods, Fragiorthods, and Haplor-
thods.
Timber harvest is the major
industry in the ecoregion. Wildlife
habitat and recreation are other
important land uses. Some alpine
meadows provide range for summer
grazing of livestock and, though
infrequent, mining for metals is
important in some areas.
Photo 10. High mountains and deeply dissected valleys are
characteristic of the Cascades Ecoregion. Patch clearcuts are
common.
19
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Photos 11 and 12. High annual precipitation and rapid
snow melt support perennial streams throughout the
Cascades Ecoregion. Steep valley walls are forested
with mixed coniferous stands including Douglas-fir,
pine, hemlock, and red-cedar.
Photo11.
Photo 12.
20
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Heavy periods of rainfall and rapid snow melt, coupled with removal of
forest vegetation and road construction for timber harvest, lead to increased
slumping, landslides, and soil erosion. This is particularly true of soils
developed on pyroclastic materials. Large woody debris in headwater reaches
may be transported downstream during major hydro!ogic events, causing scouring
and disruption of stream habitat for biota. Public recreation and mining
create localized disturbances, but are not considered major contributing
factors to stream degradation.
Sierra Nevada
The Sierra Nevada Ecoregion consists of portions of the Sierra, Trinity,
Klamath, and Siskiyou Mountain ranges, but this description will be limited to
the extent of this aquatic ecoregion in Oregon. The region is characterized by
steeply sloping, highly dissected mountains, narrow valleys with gently sloping
floodplains, and alluvial fans bordered by steeply sloping foothills (Photos
13-15). Elevation varies from 800 feet to greater than 7,000 feet, and local
relief is commonly 2,000 feet. Average annual precipitation is as low as 18
inches in some valleys and as great as 85 inches in some mountain locales.
Most precipitation occurs during the winter months, while summer months are
predominantly hot and dry. The ecoregion is 3,000 square miles in size and is
drained mainly by perennial streams. Intermittent streams occur along head-
water reaches and valley floors. Lakes are infrequent and exist mainly as
reservoirs.
Mixed coniferous forests with Douglas-fir, ponderosa pine, sugar pine,
lodgepole pine, incense-cedar, white fir, and mountain hemlock predominate in
the ecoregion, but mixed evergreen forests with canyon live oak, California
Photo 13. Steeply sloping, highly dissected mountains typify the Sierra Nevada Ecoregion.
21
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Photo 14.
Photos 14 and 15. This stretch of the Applegate
River is typical of the rocky, steep-banked streams
in the northern portion of the Sierra Nevada
Ecoregion.
Photo 15.
22
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black oak, tanoak, and madrone are common. Typical understory species are:
manzanita, ceanothus, oceanberry, rose, poison oak, blackberry, and Oregon
grape, accompanied with mats of whipple vine and twin flower. Prairie vegeta-
tion includes wild oats, fescue, and brome.
Soils in the ecoregion are derived mainly from marine volcanic and sedi-
mentary rocks, many of which have undergone metamorphosis. Upland soils are
principally Haploxerults, generally derived from sedimentary parent materials.
Haploxeralfs, derived from metamorphic parent materials, are less prevalent.
Also present are Xerochrepts formed from granitic materials, Haploxeralfs and
Haploxerolls on floodplains and alluvial fans, and Chromoxererts on alluvial
fans and bottomlands.
Timber harvest is the principal industry in the ecoregion. Forests also
provide public recreation uses. Livestock graze in prairies and under open
stands of timber. Small grains, hay, and pasture are grown on the sloping
parts of valleys for feed for dairy cattle and other livestock. Truck crops
and orchards are important in valleys with adequate water supply. Some streams
are mined for placer deposits.
Because of high potential for soil erodability, the erosion hazard to
hillslopes is severe if soils are disturbed by logging, overgrazing, or culti-
vation. Landslides and stream bank erosion are a serious problem and a major
source of sediment in streams in this ecoregion. Placer mining causes local
disturbance to biotic habitat along streams; historically, hydraulic placer
mining practices have caused major disturbance to adjacent hillslopes.
Eastern Cascades Slopes and Foothills
The Eastern Cascades Slopes and Foothills Ecoregion comprises a transition
area between the moist, rugged Cascades to the west and the variously drier
ecoregions to the east: the Columbia Basin Ecoregion, the Blue Mountains
Ecoregion, and the Snake River Basin/High Desert Ecoregion (Photos 16-18).
Elevation varies from near sea level (along the Columbia River) to over 7,000
feet, and local relief varies from 500 feet to greater than 2,500 feet. The
ecoregion is geologically young, with recent volcanic deposits in evidence as
lava flows, volcanic vents, and cinder cones. Bedrock is generally overlain by
a mantle of pumice and ash. Average annual precipitation ranges from 12 to 25
inches and occurs primarily during winter, spring, and fall months.
The density of perennial streams varies greatly throughout this 14,000
square mile ecoregion. Some areas are devoid of perennial stream flow while
other areas have greater than one mile of perennial flow per square mile.
Large streams, whose watersheds occur completely within the ecoregion, also
vary greatly in size. Their watersheds are as large as 35 square miles in the
northern panhandle of the ecoregion and 2,600 square miles in the Klamath
Basin. Perennial streams drain watersheds as small as two to three square
miles in the mountains; however, perennial flow is seldom found in watersheds
of less than 10 square miles in the lower flats. Numerous springs occur
throughout the ecoregion and natural lakes are common in areas of poor drainage
such as tableland and basin flats. Reservoirs are numerous and vary in size
from less than one square mile to well over 50 square miles (e.g., Klamath
lake).
23
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Forests of ponderosa pine predominate throughout the ecoregion, and stands
of lodgepole pine are common. The understory is generally composed of blue-
bunch wheatgrass and Idaho fescue. Green manzanita, snowbrush ceanothus, and
bitterbrush are also important understory species. Sagebrush/wheatgrass steppe
occurs in the foothills. Quaking aspen occurs in riparian and poorly drained
wet areas.
The ecoregion is dominated by large areas of immature soils developed from
volcanic ejecta, as well as soils of more advanced profile development derived
from bedrock and glacial deposits. Xeric soils of moderate rainfall and mesic,
frigid, or cryic temperature regimes are predominant, mainly as Inceptisols and
Mollisols. Cryorthods and Xerochrepts are formed from weathered bedrock,
glacial till, and volcanic debris. Deep Haploxerolls are derived from glacial
till and igneous rock. Cryandepts and Vitrandepts are formed from recent and
weathered volcanic ash and pumice. Aquolls and Aquepts are formed in basins
and on floodplains where poor drainage is a factor.
Photo 16. The Eastern Cascades Slopes and Foothills Ecoregion is characterized by
relatively gradual slopes, as compared with the adjacent Cascades Ecoregion to the west.
Timber harvest is the predominant land use; much of the forest is used for
grazing of livestock. Large tracts of the region are designated wilderness
areas or national forests, and recreation and wildlife habitat are important
land uses. A small percentage of land, mainly in valleys, is cropland for
small grain and forage.
Soils in this region are highly erodible and potential for stream bank
erosion is high. Disturbance from timber harvest and road construction can
increase hill slope erosion problems and increase stream sedimentation. In
24
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Photo 17.
Photos 17and 18. Forest stands of ponderosa pine
predominate throughout the Eastern Cascades
Slopes and Foothills Ecoregion. Timber harvest is the
principal land use. Bridge Creek at this point drains
approximately 15 square miles. Perennial flow is
seldom found in streams draining watersheds smal-
ler than three square miles in this portion of the
ecoregion.
Photo 18.
25
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grazed areas, livestock trample stream bank vegetation and upset stream bank
stability. Precipitation and perennial streams provide adequate water over
most of the region; however, water withdrawals for irrigation can deplete
stream supplies in some of the valley cropland areas.
Columbia Basin
The Columbia Basin Ecoregion (Photos 19-21) is typified by a high degree
of variability. Surrounded by a series of high mountain ranges -- the Northern
Rocky Mountains, the Wai Iowa Mountains, the Blue Mountains, and the Cascade
Mountains -- the region is characterized by deep, dry channels cut into the
underlying Columbia River Basalt formation. Elevation ranges from less than
200 feet (at the Columbia River) to greater than 4,500 feet (on some mountain
peaks), and local relief varies from less than 100 feet to as much as 2,000
feet. The landscape is composed of irregular plains, tablelands with high
relief, and low mountains. Depending upon location and elevation, average
annual precipitation is from 9 to 25 inches. Extensive loess deposits cover a
large portion of the ecoregion.
The ecoregion is 34,000 square miles in size and is drained primarily by
intermittent and ephemeral streams. Most of the perennial streams originate in
the adjacent mountainous ecoregions.
However, perennial flow can be found
in some streams draining watersheds
as small as four square miles where
water is available from groundwater
aquifers. Because of water with-
drawal for agriculture and evapo-
transpiration, these streams are
commonly ephemeral in their middle
and lower reaches (relative to more
than 20 to 30 square miles). The
larger streams that have watersheds
completely within the ecoregion drain
from 400 to 1,800 square miles.
Natural lakes are scattered and few
in number. Of the few existing
reservoirs, most are large and
located on the major rivers flowing
through the ecoregion.
The region naturally supports
sagebrush/wheatgrass steppe and
grasslands primarily of wheatgrass
with smaller amounts of bluegrass and
fescue.
Photo 19. A very large portion of the Columbia
Basin Ecoregion is in dryland wheat agri-
culture. Riparian vegetation along drainages
has largely been eliminated to maximize
acreage for cropland. Small herbs and shrubs
remain in drainage channels too deep to plow.
26
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Photo 20.
Photos 20 and 21. Channelled scablands form a complex drainage network across portions of
the Columbia Basin Ecoregion. Irrigated agriculture for pasture, potatoes, and peas occurs in
the valleys where water is sufficiently available. Diversion of stream water for agriculture often
results in intermittent streams. Wilson Creek was dry five miles downstream from this photo
point.
Photo 21.
27
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Although virtually all soils in the ecoregion have been formed under
grassland or shrub/grassland vegetation, a variety of influences from climate
and parent materials have affected soil formation. Precipitation is generally
heaviest along the margins of the ecoregion, and lightest toward the lower,
central portion. Loess deposits cover the basalt formations in southeastern
Washington and adjacent portions of Oregon and Idaho. Xerolls are the most
common soils in much of the region. Haploxerolls developed from loess and
Argixerolls developed from loess and colluvium predominate on loess hills,
mountain foothills, plateaus, and mesas. Less frequent, are: Albaqualfs,
Haploxeralfs, and Xerorthents. In the bowl-like center of the region, desertic
soils are dominant. Camborthids are the most common, but Haploxerolls,
Xerorthents, Haplargids, Haplaquolls, Torripsamments, and Rockland are also
present.
Agriculture is the major land use in this ecoregion. Much of the cropland
is in dryland wheat, although irrigated farming (mainly for potatoes and peas)
is predominant locally. Cattle grazing occurs where topographic or climatic
conditions are marginal for cultivation of wheat or irrigated agriculture. A
small acreage is in irrigated vegetables, fruit, and pasture.
Low annual precipitation and water withdrawals for crop irrigation cause
many streams to dry up during summer months. Livestock in and near streams
affect water quality both in terms of direct chemical influences and physical
habitat degradation. In many cases, beds of small streams are plowed and
re-contoured to increase area for cultivation. Where streams remain intact,
riparian vegetation is often removed or thinned to sparse, small shrub and
herbaceous species.
Northern Rockies
This ecoregion is comprised of the northern portion of the Rocky
Mountains. Rugged, high mountains are the dominant feature (Photos 22-24).
Photo 22. Rugged,
high mountains with
sharp-crested ridges
dominate the North-
ern Rockies Eco-
region. Local relief is
commonly 3,000 feet
or greater.
-------
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-------
Elevations generally vary from 1,300 to 8,000 feet, with local relief commonly
about 3,000 feet. Mountains have sharply-crested ridges and steep slopes cut
by steep-walled, narrow stream valleys. Due to the vast differences in eleva-
tion and exposure, average annual precipitation ranges from 20 inches to
greater than 60 inches. Accordingly, stream density varies greatly across the
41,000 square miles comprising this ecoregion. Density ranges from less than
one, to as much as three miles of perennial stream flow per square mile. Large
watersheds that are completely within the ecoregion average 1,200 square miles,
and perennial flow occurs in channels draining as little as two square miles.
Lakes are common in higher glaciated areas.
Coniferous stands of western white pine, lodgepole pine, western red-
cedar, western hemlock, western larch, Douglas-fir, subalpine fir, and
Englemann spruce are common. Ponderosa pine is found in some areas. Forbs and
grasses generally represent forest understory vegetation. Prairie vegetation
consists of wheatgrass, fescue, and needlegrass.
Mountain soils are derived from acidic rock types under a frigid or cryic
soil temperature regime. Dominant soils in the mountainous portions of the
ecoregion are: Cryochrepts and Xerochrepts, formed on mountain slopes;
Cryandepts, formed on ridges with thin layers of volcanic ash; and stony
Cryorthents, formed in areas of rock outcrops. Dominant soils in valleys are:
Calciorthids, Haploborolls, Argiborolls, Natrargids, and Cryoborolls, formed on
fans, floodplains, and terraces.
Timber harvest is the major economy, but wildlife habitat, recreation, and
mining are also important land uses. Open forests at lower elevations are also
used for livestock grazing. Small acreages in valleys are planted for forage,
grain, and peas.
Timber harvest and related road construction contribute towards hi 11 si ope
and stream bank erosion, resulting in large woody debris in stream channels and
increased stream sedimentation. Significant stream disturbance results from
placer, shaft, and open pit metal mining. Mine tailings in and near drainages
and disturbance or removal of stream substrates alter the physical and chemical
nature of streams, affecting habitat quality and quantity for biota.
Blue Mountains
The Blue Mountains Ecoregion is comprised of several mountain ranges
separated by fault valleys and synclinal basins. The Blue, Ochoco, Wai Iowa,
Strawberry, and Aldrich Mountains are the major ranges (Photos 25-27). Eleva-
tion varies from 2,700 feet in low lying valleys to 7,000-10,000 feet on
mountain peaks. Change in local relief is often from 1,000 to nearly 3,000
feet. Rainfall averages 10 to 20 inches annually in lower valleys and basins,
and greater than 40 inches in the mountains.
Stream drainage density varies from one and a half to two miles of peren-
nial streams per square mile in wetter areas, to no perennial stream flow in
drier areas. Watersheds of two to three square miles commonly support peren-
nial stream flow in the higher mountains; however, larger catchment areas are
necessary to support perennial flow in lower terrain. Watersheds as large as
4,000 square miles occur completely within the ecoregion. Numerous springs are
30
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scattered throughout the ecoregion, and a few clusters of alpine glacial lakes
occur in the higher mountains. Reservoirs are found on a moderate number of
streams.
The mountainous portions of the ecoregion support forests of grand fir/
Douglas-fir, ponderosa pine, and Englemann spruce/grand fir/Douglas-fir.
Stands of larch and lodgepole pine also occur. Lower elevation areas and
foothills support large tracts of sagebrush/wheatgrass steppe and wheatgrass/
bluegrass grasslands.
Soils at moderate to high elevations have been formed under forest cover
and are often derived from volcanic ash. Examples are Vitrandepts and Fragi-
orthods. In the forest/grassland transitional area, common soils are:
Haploxerolls, Argixerolls, and Palexerolls. At lower elevations, soils under
shrubsteppe vegetation are mainly Argixerolls, developed from loess and basic
igneous rock materials or from ancient lake-deposited sediments. Haploxerolls
and Haplargids are of more limited distribution.
Photo 25. High mountain ranges separated by faulted valleys characterize the Blue Mountains
Ecoregion. Higher portions of the ecoregion support forests of fir, Douglas-fir, pine, and
spruce; lower portions support tracts of shrub/grassland steppe.
Forested areas are used for timber production, grazing, wildlife habitat,
and recreation. Lower elevation shrub and grassland areas are widely used for
rangeland. Meadows on the upper mountain slopes serve as summer grazing
grounds. A very small percentage of the area is cropped for forage, grain, and
some vegetables. Many streams throughout the ecoregion have been mined
intensively for metals.
Streams and reservoirs supply water for irrigation, domestic use, and
livestock use. Livestock in and near streams affect stream bank stability and
31
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Photo 26.
Photos 26 and 27. This portion of Desolation Creek, draining about 10 square miles, is typical
of "least disturbed" streams in the Blue Mountains Ecoregion.
Photo 27.
32
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stream sedimentation. Historical overgrazing has caused a drop in the water
tables and subsequent downcutting of streams in most of the lower valleys,
accelerating deterioration of stream bank stability and sedimentation. Removal
of vegetation for timber harvest contributes toward increased hi 11 si ope
erosion. A variety of past and present mining practices have introduced
significant disturbance to stream quality. Open pit and shaft mines have had
localized effects where tailings were pushed downslope toward drainages.
Placer mining, prevalent in streams of all sizes, has resulted in major
physical disruption of stream beds and biota.
Snake River Basin/High Desert
The Snake River Basin/High Desert Ecoregion consists of the basin and
range topography of southeastern Oregon and the smooth to deeply dissected lava
plains and plateaus of southern Idaho (Photos 28-30). Basin elevations vary
from 2,500 to 5,000 feet. Mountain peaks often exceed 6,000 feet (and are
greater than 9,000 feet on Steens Mountain). Local relief is low in the basins
and plains, but 1,000 feet or greater in the mountains, and 2,000 to 3,000 foot
differences in elevation are not uncommon along some deeply incised stream
valleys. Average annual precipitation for most of the region is between 8 to
12 inches per year, increasing up to 25 inches on some mountain slopes.
Photo 28. Basin and range topography characterizes the Snake River Basin/High Desert
Ecoregion. The ecoregion is vegetated with sagebrush/wheatgrass steppe, providing exten-
sive rangeland for cattle.
The ecoregion is 57,500 square miles in size and is drained primarily by
intermittent and ephemeral streams. Most of the perennial streams in the
ecoregion are large rivers originating in adjacent, more humid ecoregions,
irrigation canals interconnected with the large rivers, and small streams
originating in the atypical, scattered mountain ranges. The small mountain
streams become intermittent at lower elevations due to irrigation, seepage, and
33
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Photo 29.
Photos 29 and 30. Crooked Creek is one of the few perennial streams in the lower elevations
of the Snake River Basin/High Desert Ecoregion. Most of the streams originating in the
scattered mountain ranges become intermittent or ephemeral when they enter the vast
basin area.
Photo 30.
34
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evaporation. Several lakes have been formed in internally drained depressions,
and vary in size from less than one square mile to greater than 50 square miles
(e.g., Lake Abert). They are shallow and, generally, saline. Scattered
springs occur throughout the region, as do a moderate number of reservoirs.
Sagebrush/wheatgrass steppe is the dominant vegetation type throughout the
region, sometimes including stands of juniper. Large tracts of saltbush/grease-
wood vegetation also occur. Some playas and recent lava flows are entirely
devoid of vegetation. Streamside vegetation is generally the same as the
surrounding regional vegetation, due to the intermittent or ephemeral nature of
most streams. Where perennial flow does occur, dense stands of sedges and
forbs line the riparian zone. In perennial streams with moderate annual flow,
woody vegetation consists of alder, willow, cottonwood, clematis, rose, and
mockorange.
Upland soils, developed under shrub and grassland vegetation, are mostly
Haplargids, Durargids, and Argixerolls, A yariety of soils are derived from
lacustrine deposits. Well drained lacustrine soils are Camborthids, Durargids,
and Durorthids; poorly drained soils are Haplaquolls and Haplaquepts. In the
northwestern portion of the ecoregion, extensive pumice deposits have produced
Vitrandepts under forest vegetation, and Camborthids and Haploxerolls under
shrub-grassland vegetation.
Most of this ecoregion is used as rangeland, though some areas in basins
or bordering large streams are irrigated for pasture and production of
potatoes, corn, alfalfa, sugar beets, and small grains.
Where access by livestock is concentrated, loss or reduction of streamside
vegetation is severe, causing stream bank erosion and sedimentation. Water
withdrawals for irrigation often result in completely dry channels downstream
from diversions.
SUMMARY
The ecoregion map of the Pacific Northwest is based on the premise that
areas of relative geographic homogeneity exist and that these areas can be
perceived by a simultaneous analysis of a combination of causal and integrative
factors including land surface form, soil, land use, and potential natural
vegetation. The map was compiled to assist managers of aquatic and terrestrial
resources to better understand regional patterns of the attainable quality of
these resources. An accompanying set of descriptions and photographs are
included to provide further characterization of the features distinguishing
each ecoregion. More synoptic analyses, at increasingly larger scales, are
necessary in order to develop a more quantitative understanding of the ranges
of attainable resource quality (within and between regions) and the associative
spatial factors that permit regional predictive capabilities.
35
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LITERATURE CITED
Archie, S. G. 1981. Surficial geology of the Puget Sound lowlands. In:
Forest soils of the Douglas-fir region. Ed. by Paul E. Heilman, Harry W.
Anderson, and David M. Baumgartner, Pullman, Washington. Washington State
University Cooperative Extension, pp. 45-59.
Anderson, J. R. 1970. Major land uses. Map (scale 1:7,500,000). In: The
national atlas of the United States of America. U.S. Geological Survey.
Washington, D.C. (revised from a map by F. J. Marschner). Plates
158-159.
Austin, M. E. 1965, revised 1972. Land resource regions and major land
resource areas of the United States. Agriculture Handbook 296. USDA Soil
Conservation Service. Washington, D.C.
Bailey, R. G. 1976. Ecoregions of the.United States. Map (scale 1:7,500,000),
USDA Forest Service. Intermountain Region. Ogden, Utah.
Baldwin, J. L. 1973. Cliamtes of the United States. U.S. Department of
Commerce, NOAA. U.S. Government Printing Office. Washington, D.C.
Crouse, M. R., and R. R. Kindschy. 1981. A method for predicting riparian
vegetation potential of semiarid rangelands. In: Acquisition and utili-
zation of aquatic habitat inventory information. Proceedings of a sympo-
sium. October 28-30, 1981. Portland, Oregon. Western Division, American
Fisheries Society, pp. 110-116.
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