Evidence suggests that western juniper
(Juniperus occidentalis) in Central Oregon affects
understory production and composition. As trees
increase in size and density, understory production is
reduced and composition changes. This study was
designed to identify the relationship between
production and composition of understory vegetation
and various tree canopy sizes of...
Expansion of Juniperus occidentalis into the sagebrush steppe has resulted in significant changes in understory composition. A consequence of increased J. occidentalis dominance may be a depletion of the seed bank. The potential for depletion is problematic because a reduction in the amount of species available from the seed bank...
Western juniper (Juniperus occidentalis) cover has more than doubled within the last century and currently occupies over 9 million acres in the Intermountain West. Encroachment has altered the spatial distribution of soil nutrients and plants in these systems, forming nutrient enriched 'resource islands,' under tree canopies. The purpose of this...
Western juniper has rapidly expanded into sagebrush steppe communities in the Intermountain West during the past 120 years. This expansion has occurred across a wide range of soil types and topographic positions. These plant communities, however, are typically treated in current peer-reviewed literature generically. The focus of this research is...
Juniper is a native species to Oregon and confers ecological benefits to wildlife when it is at savannah and transitional densities. Its range and extent have fluctuated with climatic change, but the current range expansion is unprecedented in its extent. The range expansion has been associated with the degradation of...
Western juniper (Juniperus occidentalis) encroachment has been associated with increased soil loss and reduced infiltration resulting in the loss of native herbaceous plant communities and the bird and animal species that rely on them. Hydrologically, however, change in water yield has been linked with the amount of annual precipitation a...
Since European American settlement of the Intermountain Region, dramatic changes in vegetation composition and structure have occurred in the sagebrush steppe ecosystem. Western juniper (Juniperus occidentalis spp. occidentalis Vasek), although indigenous to the Intermountain Region, has increased since the late 1800s. Considerable work has been done documenting juniper woodland expansion...
On piñon-juniper encroached sites that lack the understory fuels to carry a prescribed fire, treatment options are limited to mechanical methods. Cutting with chainsaws and leaving the trees on site has been the primary treatment method for such sites, however this method creates a potential fire hazard, particularly in the...
Knowledge of old-growth Juniperus occidentalis woodlands, which occur in central and eastern Oregon, is limited. Wise management of these woodlands necessitates a better understanding of the community ecology. The community structure of woodlands at seven sites in three areas of central Oregon was studied. Measurements taken at nine plots per...
In the Northwest Great Basin, aspen (Populus tremuloides) communities uniquely contribute to the biodiversity of a semi-arid, sagebrush-dominated landscape. In this same region, western juniper (Juniperus occidentalis) is encroaching into aspen stands. This study determined the timing, extent, and some of the effects of this expansion. Aspen stands below 2,133...
Identifying habitat and spatial requirements of wildlife species across multiple spatial scales is a challenging, yet crucial component of wildlife management. Habitat use of bats is particularly difficult to study, and managing habitat to conserve bats is especially challenging because bats are highly vagile organisms that exploit several different types...
Paired 30-day trials were conducted to evaluate
Agropyron spicatum germination when treated with two
concentrations of throughfall leachates from western
juniper slash in two stages of decomposition. Data from
a second pair of 49-day greenhouse trials were analyzed
to evaluate emergence and growth of Aqropyron spicatum,
Oryzopsis hymenoides, and Poa...
Post-settlement juniper expansion in the western states has been reported for decades,
including western juniper (Juniperus occidentalis Hook ssp. occidentalis) woodlands in the northwestern states. A 15 km2 study area in the Sheep Rock Unit of John Day Fossil Beds National Monument in eastern Oregon was selected to study spatial...
Central Oregon has attracted attention as a potential location for a biomass industry based on a locally fixed source of western juniper (Juniperus occidentalis Hook) feedstock. This study identifies a supply of juniper from private lands to determine how much of the available juniper is economically supplied at alternative prices...
A tenfold expansion of western juniper (Juniperus occidentalis spp.
occidentalis) into the sagebrush steppe has led to the degradation of the
economic and ecological potential of these landscapes. Land managers have
enacted numerous methods to reduce distributions and densities of these trees.
Assessment of above ground juniper biomass, expressed overall...
A proposed state-and-transition model (STM) for the Deep Sand Savannah ecological site in central New Mexico was developed using historical data and expert knowledge. This STM was tested utilizing data from short and long term one-seed juniper (Juniperus monosperma (Engelm.) Sarg.) control experiments initiated in 1981 and 1985. Utilizing data...
Current research indicates that the expansion of
western juniper can inhibit soil water retention, storage
and prolonged releases from watersheds. This phenomenon
is of great importance in eastern Oregon, as western
juniper is encroaching into sagebrush/grass communities
with a correlated reduction in herbaceous ground cover,
resulting in reduced infiltration rates...
This research assessed the effect of western juniper (Junlperus
occldentalls) removal on understory plant production and cover and
ponderosa pine (Pinus ponderosa) growth and plant water status.
A complete randomized block design, with four blocks and four
treatments was established in the summer of 1984 near Prineville,
Oregon. The four...
Western juniper (Juniperus occidentalis Hook) is a species of juniper native to arid regions of the Pacific Northwest. The western juniper tree has a number of competitive strategies that, in conjunction with an almost complete removal of fire from the ecosystem, have resulted in a significant expansion of its population...
Since the late 1880's western juniper has expanded in range and
increased in density in sagebrush-bunchgrass, riparian, and forested plant
communities of the Pacific Northwest. Succession to western juniper
woodland has been shown to reduce the productivity and diversity of the
understory component, result in concentration of soil nutrients beneath...
Pinyon-juniper woodlands throughout the western U.S. have expanded rapidly following European settlement during the late 19th century. In central and eastern Oregon, western juniper (Juniperus occidentalis var. occidentalis Hook.) encroachment has been previously documented in the sagebrush steppe and upper elevation aspen communities. While these vegetation changes and dynamics have...
As the management of range lands is intensified or as improvement
activity is increased, a critical need is seen to refine the
understanding of the ecology of these lands. If soil surveys on range
lands are to be meaningful and useful, the relationship between the
fundamental ecological units and the...
The influence of loss of diversity on community dynamics and ecosystem functioning has recently received considerable attention. Although study of biodiversity has a long history within ecology, empirical investigations exploring consequences of loss have been rare. Because many factors confound diversity comparisons, experimental manipulations of diversity offer the most direct...
This study examined the occurrence of coarse woody debris (i.e., pieces greater than 0.15 m in diameter and 2.0 m in length) in first- through fifth-order streams located within the Drift Creek Basin of the Oregon Coast
Range. Nine "tributary reaches" were surveyed to determine how three land management treatments...
The objectives of this study were to: 1) determine production
of plant species and utilization by cattle, sheep and deer as related
to plant communities and timber management practices and 2) evaluate
the interaction of range use between cattle and deer and between sheep
and deer as affected by site...
This research employed multivariate analytical techniques to
statistically examine the relationship between individual soillandscape
units (SLUs) in Southeastern Oregon and their associated
sagebrush communities. The objective was to determine if soil properties
between SLUs differed, describe the variation, and verify that
these differences were reflected in the taxonomic class of...
This work examined the importance of structural complexity of habitat, availability
of prey, and competition with ants as factors influencing the abundance and community
composition of arboreal spiders in western Oregon.
In 1993, I compared the spider communities of several host-tree species which
have different branch structure. I also assessed...
I compare the seasonal abundance variation, population dynamics, fecundity, egg hatching mechanism and success, and apostome ciliate parasites of the euphausiids Euphausia pac?fica and Thysanoessa spinfera from the Oregon coast, USA. Community structure and nearshore distributions were examined from bi-weekly oceanographic surveys (1970-1972). This region has a strong cross-shelf change...
Mountain Quail (Oreortyx pictus) populations have declined in many areas of the western Great Basin during the past century. Yet the life history of this species is little known. From 1997 to 2000, I studied radio-marked Mountain Quail in Hell's Canyon in northeastern Oregon, in the Cascade Mountains of southwestern...
Devil's club (Oplopanax horridum (J. E. Smith) Miq.) is an indigenous shrub of the Pacific Northwest, often found in the Tsuga heterophylla (western hemlock)/Devil' s club association in western Oregon. In the same family as ginseng, Devil's club is gaining attention for its medicinal properties. While traditional uses of Devil's...
Samples of mature vegetation from 8 of 12 major vegetational zones in Oregon and Washington, representing about 80% of the area of the two states, were studied along a latitudinal transect from the Pacific Coast
to the east slopes of the Cascade Mountains. Six stands were in forest zones, one...
This research assesses prescribed burning as a habitat management
technique in wetlands and associated upland communities of Malheur
National Wildlife Refuge, southeastern Oregon. Experimental burns
were conducted to evaluate fire behavior and effects in wetland and
upland habitats, and, fire effects on Cirsium arvense. Wetland plant
communities were monotypic stands...
This is a study of the ecology of the timberline and alpine vegetation of the Three Sisters which are located in the
central Oregon Cascades. The Sisters are a close group of three 1O,000-foot volcanic peaks. Volcanic activity within the last few hundred years as well as recent glaciation have...
The protection of water quality and the maintenance of productive
anadromous fisheries is a primary concern in the Pacific Northwest.
Excessive suspended sediment loads is a principle water
quality problem on small wildland watersheds in this region (Anderson,
1971; Brown, 1972). Man's activities have been shown to increase
sedimentation rates...
Ecological and historical information are combined in examining the environmental influence of fire and grazing on rangelands in eastern Oregon through time. Competitive relationships between herbaceous and woody flora in the northern Great Basin are discussed, focusing broadly on the shrubsteppe regions 'of Franklin and Dyrness (1973) but with special...
The effect of forest shrub vegetation on soil moisture,
temperatures evaporation potentials and the survivals growth and
bud activity of five species of Pinus was studied on planting
sites placed on opposite exposures on two locations in southwest
Oregon and northeast Mexico. Treatments applied were: Manual
slashing; Manual slashing plus...
Detailed phytosociological and physical data were gathered from six grass-fern balds in the Oregon Coast Range, Monmouth Peak, Grass Mountain, Prairie Peak, Roman Nose Mountain, Tyee Mountain, and Saddle Mountain. Panchromatic and color infrared air photography guided sampling within individual balds. The resultant floristic data was manipulated by a Braun-Blanquet...
Slow moving earthflows (0.1 15 m/yr.) may constrict valley
floors and directly impinge on stream channels. Earthflows that
move laterally into channels deliver organic and inorganic material
to the stream from the earthflow toe. If the amount and particle
size of this material is too large to be removed by...
Ranchers and resource managers have become concerned about the
role and spread of Cardaria draba (L.) Desv. (whitetop) in the sagebrush
steppe of Northeastern Oregon. This area is an important natural resource
for livestock production and big game winter range.
An area near Keating, Oregon was selected to study the...
Fire history and fire regimes were reconstructed for a 450 km² area in the central
western Oregon Cascades, using tree-ring analysis of fire scars and tree origin years at
137 sampled clearcuts. I described temporal patterns of fire frequency, severity, and size,
and interpreted topographic influences on fire frequency and...
Riparian areas that can be used as reference sites on which to base goals of vegetation restoration have not been documented in the Oregon Coast Range. I examined the composition and distribution of unmanaged riparian overstories in the central Oregon Coast Range along nine streams which have experienced minimal disturbance...
The purposes of this study were:1) to review the land use history of Oak Creek watershed since European settlement. And 2) to consider the human-caused impacts and their effects associated with different land uses. The study area was classified into three land use patterns: residential,agricultural, and forested areas.Since the European...
The extent of biological invasions, their role on the feeding of
native fishes and their impact on community stability were
investigated in Alsea Bay and Yaquina Bay, two estuaries on the
central Oregon coast, USA. Most nonindigenous species (NIS)
introduced in these intermediately invaded estuaries are
considered byproducts of culturing...
Riparian vegetation (trees > 10 cm dbh), woody debris (> 10 cm diam, > 1 m long), channel, and landform characteristics were inventoried in mature (80-150 yrs) and old-growth riparian areas (>250 yrs) selected from small tributaries of the Coos and Coquille River basins in southwestern Oregon. Basal area of...
Factors affecting the persistence of mussels (Mytilus californianus) and their associated epibiont species were studied along the central Oregon coast. Interactions between mussels and their algal epibionts (Endocladia
muricata) varied in sign and strength with environmental conditions. In extreme temperatures mussel—epibiont interactions determined survival of individual mussels,
and persistence of...
In an effort to describe the plant communities and
succession of the Oregon coastal grasslands, vegetation
and environmental data were collected from 75 stands at
24 separate locations ranging from Cape Falcon in Tillamook
County to Cape Ferrelo in Curry County. The vegetation
data consisted of cover and frequency values...
Waldo Lake, located in the Oregon Cascades, is
considered to be one of the most dilute lakes in the
world. Even with very low nutrient concentrations and
sparse populations of zooplankton, introduced fish in the
lake are large in size and in good condition when compared
to fish from other...
Species richness and abundance of forest floor bryophytes, including epiphytes from incorporated litterfall, were assessed at two sites in western Oregon. Bryophyte diversity, abundance, and community composition were compared between sites, and between young forest stands ([approximately] 55 yrs.) and old-growth stands (400+ yrs.) within each site. Relationships of stand...
The tree species and size structure of 9l old-growth forests dominated by Douglas-fir
in central western Oregon was characterized using complete inventories of all trees larger than 20cm dbh over a mean area of 17.1ha at each site. Douglas-fir accounted
for over 75% of the total average basal area (39.1...
A study of the McKenzie River floodplains, terraces and glacial
outwash plains was undertaken to classify and describe the vegetation
and soils of a previously little studied synecological unit.
During the summer of 1971, 54 analytic vegetation and soil
plots (stands) were studied. Cover and frequency of all trees, shrubs,...
Research was conducted on the Keating rangelands in north-eastern Oregon to determine the food habits of deer and cattle and
similarity of their diets, and to estimate deer and cattle months of
grazing on both a quantitative and nutritional basis. Data were
collected during the winters of 1978-1979, 1979-1980 and...
Total length and biomass of fungal mycelium in the soil of a young Douglas-fir stand in the central Oregon Coast Range were estimated over 27 months with the agar-film technique. In a second study, phenology and taxonomy of hypogeous (belowground) sporocarps were studied over 32 months in a nearby, young...
Studies were conducted from 1962 to 1966 to investigate the
effectiveness of several practices in manipulating medusahead
(Taeniatherum asperum (Sim. ) Nevski) infested and/or dominated
ecosystems by releasing competition in favor of perennial grasses.
Several herbicide treatments were evaluated for selective
control of medusahead and cheatgrass (Bromus tectorum L. )...
Benthic samples were collected during the summer, winter and
spring seasons from upper Yaquina Estuary, a region used by Georgia-
Pacific Corporation for log dumping and storage. Samples came from
an active log dump and storage areas as well as areas not associated
with log handling activity. The samples were...
The vegetative communities in the subalpine meadows of Hunts
Cove, Mt. Jefferson, and some of the major environmental factors
affecting them were studied in the summer of 1971. Hunts Cove is in
the subalpine Tsuga mertensiana parkland of the Central Oregon High
Cascades. Habitats within the Cove vary considerably; elevation...
Classification of Streams and stream habitats is useful for research involving establishment of monitoring stations, determining local impacts of land use practices, generalization from site-specific data, and assessment of basin-wide, cumulative impacts of human activities on streams and their biota. This thesis presents a framework for a hierarchical classification system,...
Riparian forests in the central Oregon Coast Range vary along a coniferous-deciduous compositional continuum. Variations in structure and composition affect water quality, fish and wildlife, biodiversity, timber, and aesthetics. A retrospective approach was taken in this study in order to understand and compare the structure, pattern, and history of an...
Nutrient and particulate matter balances were established for five ecosystems dominated by Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] in the western Cascades, Oregon. Carriers of N and P were particulate matter (dust in precipitation and sediment in streams) and dissolved matter in both precipitation and stream water. The input and outflow...
Variability of plant species distributions, plant connunities,
soil and hydrological factors in an area of the Netarts Spit tidal
marsh are examined. The purpose is to advance general understanding
of Oregon's tidal marsh ecosystems in terms of plant coninunities and
functio'nal habitat conditions and make a contribution to the conceptual...
Nehalem Bay is located on the northern coast of Oregon in Tillamook County and contains approximately 243 ha of salt marsh. The Nehalem marshes occur as islands and land-tied units. West Island is the largest marsh island with an area of 82.9 ha and a maximum elevation of 3.079 m...
I examined the biomechanical factors that influence the sizes of intertidal macroalgae by studying a population of Fucus gardneri at Fogarty Creek Point, OR. I constructed a mathematical model to predict optimal sizes and probabilities of survival for Fucus under conditions of high and low wave exposure. Predicted optimal sizes...
Invasive plants have the potential to reduce the diversity of species in plant and animal communities. I examined the negative effect of two invasive wetland plants, purple loosestrife and reed canary grass, on the species richness and diversity of plant and moth communities within 24 wetland study sites in the...
Riparian areas in the Pacific Northwest provide important biotic and abiotic
features, such as down wood, moist microsites, and abundant invertebrate prey that
benefit aquatic and terrestrial amphibians. Reported high densities of amphibians from
streams and riparian areas in the Pacific Northwest highlight their importance in riparian
food webs. Amphibians...
Rangelands span over 50% of the globe and approximately 70% of the United States. Although livestock production is an important use of rangelands, the benefits of rangelands are highly diverse. Humans find intrinsic value in protecting these unique and variable landscapes for wildlife, vegetation, and recreation enthusiasts. Woodland plant encroachment...
A study was initiated in 1961 to characterize seral plant
communities in a part of the Cedar Creek drainage in the Tillamook
Burn. Stratification of vegetation into ecological units was a necessary
first step in conifer-animal damage studies supported by the
Oregon State Game Commission.
Reconnaissance information was recorded in...
Juvenile coho salmon (101-400 mm) were sampled by
purse seine off the Pacific Coast from Waatch Point,
Washington to Four Mile Creek, Oregon, out to 30 mi
offshore, during the months of May, June, and September in
1982 and 1983. Sea surface temperature, surface salinity,
surface chlorophyll-a concentration, and Secchi...
The use of high throughput molecular methods that allow for the study of bacterial communities in environmental samples is commonplace in microbial ecology. Until recently, fungal community ecology has
focused on isolation, collection of sporocarps, or collection of ectomycorrhizal roots. The techniques used to extract and amplify DNA from environmental...
This study investigates patterns of physical structure organization in stream
networks. In particular, it seeks to describe patterns of wood, boulders, pools and slope
that are evident in stream channels and to determine whether patterns of these elements
are influenced by network-level controls. The four in-stream parameters were
combined to...
As part of a hierarchical approach to classifying watersheds and stream habitats based on geomorphic and geologic criteria, we defined ten classes of fluvial and lacustrine habitats at the scale of valley segments. Valley segments are landscape units which encompass surface waters and the adjacent floodplains and hillslopes with which...
The purpose of this thesis is to provide a first look at the spatial and temporal distributions of dissolved organic material (DOM) off the Oregon coast of North America. While this paper is not a comprehensive examination of these distributions, several patterns are identified as promising candidates for continued research....
Samples of benthic organisms off the coast of Oregon, taken
from depths varying from 50 to 2900 meters, have been analyzed in
terms of diversity at a given station, and similarity and ecological
distance to other stations. Estimates of epifauna abundance were
also made. In the analysis an important distinction...
The structure and components of riparian areas influence the rate, amount, and timing of water, nutrients, organic debris, and inorganic materials that enter streams and rivers. The energy of floodwaters and their ultimate volume, timing and erosive power is influenced by the soils, vegetation and geomorphology of fluvial surfaces within...
I studied spring food habits, focusing on cambium-feeding, of black bears (Ui-gus americanus) in the Central Coast Ranges of Oregon (1987-90) by comparing an area with high levels of timber damage caused by bears (north area) with an adjacent area of low levels of bear damage (south area). I also...
Craterellus tubaeformis is a small to medium-sized forest mushroom that is fairly common in the Douglas-fir/western hemlock forests of the Pacific Northwestern United States and is most often associated with decayed coarse woody debris. In this study, the mycorrhizae of Craterellus tubaeformis in western Oregon is identified by DNA analysis...
As a key factor contributing to slope stability, in-stream habitat for aquatic species (e.g., salmonids), nutrient cycling, and corridors for upland species, riparian vegetation and its maintenance is of critical conservation importance. Subsequently, the chronic degradation of aquatic and riparian ecosystems in the semi-arid and arid landscapes of the western...
Managing riparian buffer zones is a potentially important approach to protecting streams from agricultural pollution. This study was conducted to determine if a pasture, a hybrid poplar (Populus trichocarpa x deltoides) stand, or a native oak (Quercus garryana) forest, had the greatest potential to serve as a nutrient buffer zone....
A crossdated fire history was reconstructed for a 1562 km2 area in the southern Willamette foothills of Oregon, using fire scars and tree origin years from twelve sites. The purpose of this study was to determine fire frequency for each site and to quantify temporal and spatial variability of fire...
Much of the native riparian vegetation of the Willamette Valley, Oregon, has been replaced with agricultural crops or invasive non-native plant species. Detailed information about current Willamette Valley riparian vegetation is generally lacking. Plant specie composition data are useful in a variety of applications, including condition assessment, environmental monitoring and...
The Northern California Current (NCC) ecosystem exhibits extreme seasonal, interannual and interdecadal shifts in the abiotic environment and shifts in primary and higher production. This variability is also apparent in the spatial structure of the ecosystem with nearshore-shelf waters (<150 m isobath) being highly productive and having a different community...
This study consisted of two research projects in the Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh) alliance, the most extensive of the big sagebrush complex in the Intermountain West. In the first project, we intensively sampled 107 relatively undisturbed, late seral Wyoming big sagebrush...
Relatively recent increases in ponderosa pine abundance have effected unprecedented changes to ecosystem structure and function. Efforts to restore ponderosa pine systems are often focused on the manipulation of tree structure and the re-introduction of a more natural fire regime. Successful restoration should also incorporate understory components but information addressing...
Seven streams, one of them permanent, were studied in
western Oregon, USA. The research was designed to assess
the value of summer-dry headwaters for conservation
oriented landscape management. Streams were categorized
primarily according to exposure (forest versus meadow
sites) and secondarily according to flow duration
(ephemeral = short-flow versus temporary...
Grazing of riparian forage by livestock may alter stream channel morphology in ways that impact nearby aquatic habitat, bank stability, vegetative cover and water quality. A number of grazing management practices have been proposed as a means to reduce the amount of time cattle spend in the riparian zone. The...
I studied riparian forests of four western Oregon watersheds (dry south to wet north) to determine the multiscale controls on woody riparian vegetation. I conducted separate analyses of controls on plant distribution, diversity, and tree regeneration using vegetation and environmental data collected in two related field studies: (1) a multiscale...
To effectively manage for biodiversity at broad, ecosystem scales, the influences of habitat structure at multiple spatial scales on vertebrate species must be understood. There are few studies on the broad-scale habitat requirements of stream amphibians despite their importance in streams in forest ecosystems in the Pacific Northwest (PNW) as...
This study was designed and implemented to observe
the spatial and temporal dynamics of groundwater levels
and temperatures adjacent to a beaver pond in semi-arid
central Oregon. The study site was located on the eastern
boundary of Painted Hills National Monument along Bridge
Creek, a tributary to the John Day...
We monitored larval Lost River and shortnose suckers from natal beds in the Williamson and Sprague rivers to nursery grounds in Upper Klamath Lake. Downstream movements occurred at night, in the middle of the channel, and on the falling limb of the hydrograph. Ages, sizes, and developmental stages of larvae...
Forest associations, secondary succession, and relationships
of plant communities to Roosevelt elk were investigated. Stratification
of vegetation into ecological units and an understanding of secondary
succession by habitat-type were a necessary first step in investigations
into browsing of conifers by elk. The study was jointly conducted
by the Oregon State...