Human activities are causing profound changes to the global environment, yet the potential consequences of these changes on rising atmospheric carbon dioxide and climate change are not well understood. Improving our understanding of these processes requires an enhanced awareness of how global ecosystems are changing and how these changes affect...
The cinnabar moth (Tyria jacobaeae (L.), Lepidoptera: Arctiidae) is an icon in
population ecology and biological control that has recently lost its shine based on evidence
that (1) it is less effective than alternatives (such as the ragwort flea beetle Longitarsus
jacobaeae (Waterhouse) (Coleoptera: Chrysomelidae) for controlling ragwort Senecio
jacobaea...
This thesis provides the first general description of the natural variation in age
structure, growth rates, and survival in headwater populations of coastal cutthroat
trout Oncorhynchus clarkii clarkii from western Oregon, and a subsequent
synthesis of these life-history characteristics across the range of the subspecies.
Age, growth, and survival were...
I used current water management practices in central and eastern Oregon and Washington as natural experiments to quantify the effects of irrigation water withdrawals on macroinvertebrate community structure and life history strategies. Reduced discharge had direct (e.g. decreased velocity and wetted habitat) and indirect (e.g. increased conductivity and temperature) effects...
To begin to understand freshwater seasonal floodplain fish communities in the context of human alteration of the physical system, species introductions and wetland restoration efforts, I studied fish assemblages in fifteen seasonal floodplain wetlands within four geographic regions (coastal, upper Columbia River estuary, Puget Sound and eastern Oregon/Washington) in the...
Reforestation-based restoration of severely burnt plantations is one of the primary management activities following wildfire on U.S. federal lands. Restoration effects on early-seral plant and cryptogam communities have not been documented. The objectives of this study were, in severely burnt plantations two to four years post-fire, to examine the: (1)...
I studied selection of winter den sites by northern flying squirrels (Glaucomys sabrinus) in forests of the Oregon Cascades. Fifty-six squirrels were radio-collared in three managed, 80- to 1 30-year-old Douglas-fir stands on the Umpqua Nationa Forest during the winters of 1994-95 and 1995-96. Squirrels were located at their den...
The widespread introduction of trout to naturally fishless mountain lakes in the western United States has been accompanied by little research. The ecological role of trout populations occurring in 91 lakes of the central Selway Bitterroot Wilderness, Idaho, was examined with respect to 1) the sampling variability of biological and...
Prairies were once the dominant vegetation type in Oregon's Willamette Valley. Land use conversion, fire suppression, succession, and invasive species have reduced Willamette Valley prairies to less than 1% of their historical area. The remnant prairies that persist today are small in size and are highly fragmented. Marginal strips of...
Hardwood lumber is a major forest product, and board grading is an important part of its manufacturing and marketing. Computer grading programs have been used to train graders and to grade lumber for board data banks, but they have not been used to machine-grade boards in an industrial environment because...
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...
Trees that survive disturbances can form a prominent legacy which may influence
post-disturbance successional pathways. The effects of biological legacies on community
dynamics is a critical question in ecology. In the present study, I examined two mapped
stands in which old-growth remnant trees, survivors of partial fires, emerge above a...
Fire is a fundamental disturbance that drives terrestrial and atmospheric carbon dynamics. Previous studies have quantified fire effects on carbon cycling from local to global scales but have focused nearly exclusively on high-severity, stand-replacement fire. Since 2002, variable-severity wildfires have burned more than 65 000 ha across the east slope...
Evaluating the relative influences of positive and negative interactions in shaping communities is a major topic in modern ecology. Facilitative interactions between basal species are important in habitats with intense predation pressure or severe abiotic stresses. However, few studies address the potential for positive interactions between trophic levels to influence...
Salmonberry community structure was examined in alder-dominated
riparian buffer strips in the Oregon Coast Range. Salmonberry growing on slopes
was found to respond differently, to both characteristics of the buffer strips and
to environmental factors, than salmonberry growing on terraces.
Salmonberry, as measured by total height, number of ramets or...
Knowledge about vegetation patterns and ecological processes in unmanaged, late-successional
watersheds is needed to provide a foundation for forest management strategies
aimed at conserving native biodiversity. I examined influences of environmental variability
and disturbance history on forest structure and composition in the Cummins Creek
Wilderness, located on the central Oregon...
The body size (W) of animal species is one of the best predictors of
population density (D) when large assemblages are considered. It has been
shown that theoretically the D-W relationship can be the consequence of two
other distributions: the log-normal distribution of body sizes of the species and
of...
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...
The forest alpine tundra ecotone (FTE, also known as alpine treeline or subalpine parkland), is a conspicuous feature of mountain landscapes throughout the world. Climate change-driven increases in temperature are believed to result in FTE movement and tree invasion of subalpine meadows, which have been documented throughout the Northern Hemisphere...
The general objective of this study was to develop
models and datasets that would significantly advance our
ability to assess the current and future effects of global
change on the biosphere. The focus was in two areas: (1)
preparing environmental datasets at regional to small
watershed scales; and (2) developing...