Forest managers of public lands in western Oregon and Washington have become increasingly interested in creating additional conifer cohorts in young, even-aged, second-growth Douglas-fir stands. The purpose of our research was to assess the establishment, survival, and growth of naturally-regenerated and underplanted conifers 10-13 years after overstory thinning and understory...
Previous research examining the influences of post-fire salvage logging on abundances of birds has focused primarily on the response of cavity-nesting species. There is limited research in regard to the impact of salvage logging on a broader range of bird species. In addition, little is known about how different intensities...
Bale Mountains National Park (BMNP) is currently considered the most important conservation area in Ethiopia. BMNP was established over forty years ago to protect Ethiopian endemic fauna and to preserve an array of habitat types including Afroalpine, Afromontane, and the second largest natural humid forest (Harenna forest) left in Ethiopia....
Intensive forest management (IFM, dense conifer plantings and herbicide applications) may alter the characteristics of early seral plant communities that function as major habitat resources for a host of wildlife species, including cervid herbivores such as Cervus elaphus and Odocoileus hemionus. Such large herbivores can also substantially affect plant community...
Two case studies of 5 ecosystems were used to examine the nitrogen fixation rate of red alder (Alnus rubra Bong.), varnishleaf (Ceanothus velutinus var. laevigatus (Hook.) T. & G.), deerbrush (C. i ntegerrimus H. & A.), and snowbrush (C. velutinus var. velutinus Dougl. Ex Hook). The first case study assayed...
Investigations of the Pleistocene peopling of the New World require archaeologists to establish an understanding of the paleoenvironmental conditions that would have affected early foraging peoples. Other studies have focused on the timing and route of migration and the peopling of the Americas. This project contributes to the body of...
This collection of three manuscripts serves to improve methods for collecting, interpreting, and utilizing autocorrelated data from headwater stream networks. Each stream network is comprised of linear segments. These segments lie within a unique branching structure that connects the segments via flowing water, and the connectivity provided by water varies...
Tree species directly and indirectly affect soil nutrient cycles. I sought to characterize soils and foliage associated with four common canopy tree species (Douglas-fir, western hemlock, western redcedar, and bigleaf maple) in mixed-species old-growth forests of the Oregon Coast Range and to determine whether and how soils differ among the...
Native America tribes and community members throughout Oregon have asserted a strong opposition to the fossil fuel industry’s attempt to expand railways, build pipelines, and construct refineries, holding facilities, and export terminals. Despite the limited presence of fossil fuel infrastructure in the state, however, the industry is actively pursuing permits...
Small pelagic fishes (SPF), such as anchovies and sardines, are ecologically important due to their large abundance and intermediate trophic position that links plankton production to upper trophic levels. They are also economically important, supporting large fisheries that contribute to one fourth of the world fish landings. Reproductive success in...
Ungulates comprise some of the most well researched and intensely managed wildlife populations on earth. As such, they are recognized as ideal study subjects for developing and modifying management tools or theories (Danell et al. 1994, Shipley 2010). An introduced moose (Alces alces gigas) population on the Copper River Delta...
Large areas of non-coniferous communities in southwestern Oregon are thinned to reduce fire hazard and accomplish ecosystem restoration, under the assumption that current fuel loads are unnaturally high. Although Oregon white oak (Quercus garryana) woodlands are a characteristic landscape component in this region, little is known about their current or...
I studied presence, relative abundance, and resource selection of bats in managed Douglas-fir (Pseudotsuga menziesii) forests in western Oregon from May through September, 1999–2001. Species richness was not related to elevation, density of snags, or length of edge or perennial streams in sampled landscapes. I captured bats more frequently in...
We conducted capture and acoustic surveys for bats in six areas along a latitudinal gradient in Southeast Alaska from mid-May to September in 2005 and we continued surveys on Prince of Wales Island from mid-May to September in 2006. We determined the level of effort required to catch each species...
Vegetation provides food for many insects, and many insects serve as food for bats. We investigated the linkages among these three trophic levels in riparian areas throughout the Oregon Coast Range by examining the influence of vegetation cover, composition, and structure on the activity of nocturnal insects and bats, the...
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E. Macro-moths captured in conifer- and deciduous-dominated stream reaches..... 212
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Mixed-severity fire occurrence is increasingly recognized in Pseudotsuga forests of the Pacific Northwest, but questions remain about how tree mortality varies, and forest structure is altered, across the disturbance gradient observed in these fires. Therefore, we sampled live and dead biological legacies at 45 one ha plots, with four 0.10...
Fundamental objectives in the field of conservation biology involve understanding the processes that influence small and declining populations and applying that knowledge to develop appropriate monitoring strategies and targeted management and conservation actions. Critical first steps in determining the relative role of factors that drive population declines involves estimation of...
The genus Phytophthora contains some of the most destructive pathogens of forest trees, including the most destructive pathogen of alder in recent times, Phytophthora alni. Alder trees were reported to be suffering from canopy dieback in riparian ecosystems in western Oregon, which prompted a survey of alder health and monitoring...
The diverse lichen flora of the Pacific Northwest is being impacted by
population growth and by forest management practices. Accumulating information
about our lichen flora will improve our conservation strategies. This dissertation first
collects information to improve our understanding of how lichen communities vary
among forests of differing structure, and...
Prairie-oak ecosystems in the Willamette Valley, Oregon have experienced habitat loss and degradation; most of these ecosystems are fragmented into smaller patches. Prairie-oak butterfly species, in the Willamette Valley, have decreased dramatically due to loss or degradation of habitat. More research is needed on sustaining the populations of butterflies in...
Fuels management on Bureau of Land Management lands in SW Oregon, USA, is motivated by the needs to reduce fire hazard and restore ecosystems thought to be impacted by fire suppression. Chaparral is one of the most characteristic vegetation communities of SW Oregon's interior valleys, and extensive acreages within this...
There is renewed interest in agroforestry as a management strategy for marginal agricultural lands in western Oregon. Silvopastoral systems combine tree and
forage production, which involve crops and practices familiar to the area. The objective of this study was to determine how
management influences the physiology and ecological interactions of...
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...
Deforestation, accelerated soil erosion, and land degradation are serious problems in Ethiopia. The uncontrolled removal of natural forests, demographic pressures and cyclical drought has aggravated the situation, resulting in massive environmental degradation and a serious threat to sustainable agriculture and forestry. To overcome these problems efforts have been made to...
Canopy gap formation is a major factor contributing to maintenance of overstory species diversity and stand structure in forests and may be integral to development of understory shrub and herb layers as well. Acknowledgement of gap formation as a fundamental feature of natural forests has led to consideration of gaps...
Fire is a major disturbance process in many forests. Long-term studies of the biogeochemical effects of fires, especially on soils, are very rare.
Consequently, long-term effects of fire on soils are often hypothesized from
short-term effects. In a chronosequence study, I studied 24 western Cascades
(Oregon) forest stands thought to...
Previous studies of bird communities in the mid-Willamette Valley, Oregon, indicated that Oregon white oak (Ouercus garryana) stands supported more cavity-using bird
species than sympatric stands of Douglas-fir (Pseudotsuga menziesii). Mature Oregon oak stands are being harvested and few are regenerating. I compared cavity availability for hole-using fauna among 10...
Ecosystem nitrogen (N) supply strongly influences the availability and cycling of other essential nutrients in temperate forests, especially calcium (Ca). Short-term additions of N that exceed ecosystem demands often increase dissolved nitrate fluxes and decrease soil pH, which can stimulate soil Ca loss. However, the long-term effects of high N...
Various methods have been used to estimate the amount of above ground forest biomass across landscapes and to create biomass maps for specific stands or pixels across ownership or project areas. Without an accurate estimation method, land managers might end up with incorrect biomass estimate maps, which could lead them...
Several studies of herbaceous perennials have addressed the effects of environmental factors during and after production, inherent cold hardiness, and post-harvest handling procedures to enhance flowering and growth during establishment. The regrowth of both woody and herbaceous forage plants following establishment is reported to be directly related to reserve-nitrogen content....
Stem rust, caused by the fungus Puccinia graminis subsp. graminicola, can cause yield reductions exceeding 90% on perennial ryegrass (Lolium perenne L.) crops grown for seed if not treated with fungicide in the spring. There is evidence that late-spring stem rust epidemics are initiated by populations that survived the winter....
In response to concerns about excessive stand densities and high-severity wildfires, land managers in the western United States are carrying out extensive programs of fuel reduction thinning. How will these sudden reductions in canopy cover and associated changes in habitat affect native and exotic herbaceous vegetation and canopy species regeneration?...
This study examines the long-term role of interference on stand development of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) and red alder (Alnus rubra Bong.) planted mixtures in the Central Cascades of Oregon, USA. The two species are common associates in naturally regenerated and planted conifer stands in the Pacific Northwest. Due...
Silvicultural canopy gaps are emerging as an alternative management tool to accelerate development of complex forest structure in young, even-aged forests of the Pacific Northwest. I investigated patterns of nitrogen (N) availability along transects through 0.1 and 0.4 ha silvicultural gaps in three 50-70 year old Douglas-fir forests of western...
Sagebrush steppe ecosystems are one of the most widespread but endangered ecosystems in North America. A diverse array of human-related stressors has gradually compromised these ecosystems' resilience to disturbance and invasion by Bromus tectorum (cheatgrass). The role of the foundational shrub Artemisia as a driver of herbaceous community structure and...
Disaggregative and individual-tree/distance-independent modeling methods are
compared and contrasted. Differences between the two are related to differences in functional
and apparent resolution and may be illustrated using aggregation theory. When considering
models of different levels of resolution describing a given phenomenon, invariance with respect
to the aggregation implied (symmetry) may...
Population trends and patterns in species distributions are the major currencies used to examine responses by biodiversity to changing environments. Effective conservation recommendations require that models of both distribution dynamics and population trends accurately reflect reality. However, identification of the appropriate temporal and spatial scales of animal response, and then...
Models of weed communities aid in the development of
weed management strategies and elucidate the processes
and mechanisms that regulate plant populations and
communities. A conceptual weed community model was
developed to organize key regulatory life-history
processes. Specific investigations focused on the
processes of plant growth and competition, and
relationships...
Fire severity is hypothesized as an important driver of bird responses to wildfire. For those species that typically respond negatively to increasing severity, Accessibility of high-severity burned forest may be dependent on the proximity of unburned or low-severity burned forest to meet all of the needs of breeding bird species...
Headwater streams are generally small, first-order streams that can comprise up to 80% (by stream length) of the drainage network in mountainous areas of the Pacific Northwest. These streams are intimately connected with downstream reaches, serving as a source of sediment, woody debris, organic matter and nutrients. The surrounding forests...
This thesis examines the competitive aspects of Douglas-fir trees growing with two commonly associated competitors--red alder and grass--at varying densities. Two Nelder plots in three different environments in the Oregon Coast Range were studied. The sites represented the warm, dry climate of the Willamette Valley; the warm, moist climate of...
This thesis research examines the effects of film-forming antidesiccants applied to dormant pondexosa pine (Pinus ponderosa Dougl.) seedlings after being lifted and to actively growing seedlings. The basic proposition was that antidesiccants would have a positive effect on reducing water loss in ponderosa pine seedlings. In order to evaluate the...
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...
This dissertation describes arthropod responses to and effects on decay processes in ponderosa pine, a dominant forest canopy tree in northern California. We used both descriptive and experimental field techniques to establish how arthropod assemblages depend on and are important to the disintegration of woody structures in forests of this...
Land use alters the physical and biological structure of stream ecosystems and potentially alters their capacity to process nitrogen (N), an essential nutrient that has nearly doubled in abundance on the biosphere
during the past century from human activities. In this dissertation, I quantified uptake and transformation of nitrate (NO₃⁻)...
Chlorinated and non-chlorinated solvents are used in a variety of industrial processes and as a consequence, they have become environmental contaminants as well. Because of this, they lead to both occupational and environmental exposures. Exposure to these compounds can potentially result in various forms of neurological damage with a wide...
Pollination is an essential ecosystem service that sustains functioning ecosystems and aids in food production. In response to recent, widespread declines of managed and native bee populations, many land managers have shown interest in developing conservation and restoration plans for enhancing native bee habitat. However, there is a lack of...
Since 2007, electronic cigarette (e-cigarette) sales in the U.S. have surpassed those of tobacco cigarettes. This is due, in part, to manufacturer’s claims that they are a safer alternative to tobacco cigarettes. However, formaldehyde, acrolein, and diacetyl have been detected in e-cigarettes and public knowledge of e-cigarette composition and potential...
