Forest Sciences Commons^™

Urban Impacts To Forest Productivity, Soil Quality, And Canopy Structure In Forest Park, Portland, Oregon, Andrew David Addessi

Dissertations and Theses

Land use practices and exposure to low impact disturbances associated with an urban environment can alter forest structure and function. Past and ongoing research in Forest Park, a large urban forest in Portland, Oregon, suggests that mature mixed Douglas-fir (Psuedotsuga meziesii)-hardwood stands in the more urban end of the park lack a shade-tolerant conifer understory composed of the late successional conifer tree species, such western hemlock (Tsuga heterophylla) and western red-cedar (Thuja plicata). 5-year plot remeasurement data that characterizes productivity and mortality patterns did not show a strong relationship to urban proximity. Plot productivity …

Fire Modulates Climate Change Response Of Simulated Aspen Distribution Across Topoclimatic Gradients In A Semi-Arid Montane Landscape, Jian Yang, Peter J. Weisberg, Douglas J. Shinneman, Thomas E. Dilts, Susan L. Earnst, Robert M. Scheller

Environmental Science and Management Faculty Publications and Presentations

Content Changing aspen distribution in response to climate change and fire is a major focus of biodiversity conservation, yet little is known about the potential response of aspen to these two driving forces along topoclimatic gradients.

Objective This study is set to evaluate how aspen distribution might shift in response to different climate-fire scenarios in a semi-arid montane landscape, and quantify the influence of fire regime along topoclimatic gradients.

Methods We used a novel integration of a forest landscape succession and disturbance model (LAN DIS-II) with a fine-scale climatic water deficit approach to simulate dynamics of aspen and associated conifer …

Understory Species Patterns And Diversity In Old-Growth And Managed Northern Hardwood Forests, Robert M. Scheller, David J. Mladenoff

Environmental Science and Management Faculty Publications and Presentations

Forest management can significantly affect both the diversity and spatial patterning of understory vegetation. However, few studies have considered both diversity and spatial patterning at a stand scale. Our objective was to evaluate the effects of forest management on understory plant communities in northern hardwood forests and assess the processes governing differences in species composition, diversity, and spatial patterns. We sampled understory vegetation (all speciestall) and percentage of light transmission levels in three forest types in 12 mesic northern hardwood stands in northern Wisconsin and the Upper Peninsula of Michigan, USA: old-growth, undisturbed forests; even-aged forests resulting from clearcut logging …

Changes In Populations Of Soil Acari During The First Year After Clearcutting, Sue Ellen Orlaske

Dissertations and Theses

Soil samples taken from a clearcut and adjacent uncut site of a Douglas Fir and Western Hemlock old growth forest in the Cascade Range of southern Washington showed greatly reduced adult and juvenile population densities of macro-phytophagous, microphytophagous, and predatory soil acari in the clearcut. These effects appeared to be due to high lethal summer litter temperatures and reduced pore spaces due to scarification. Also, the number of species of acari in the clearcut was lower than in the control after clearcutting.

The Allelopathic Potential Of Rhododendron Macrophyllum In A Western Cascades Clearcut, Ivan W. Clark

Dissertations and Theses

The purposes of this study were to determine if Rhododendron macrophyllum has the potential to inhibit the growth of other species through the production of water-soluble toxins which are leached out of its litter by rainfall, and to determine if this potential is realized in the field. The study was therefore composed of two part: 1) a series of bioassays to determine the presence an activity of water-soluble phytotoxins in R. macrophyllum leaf litter, and 2) a field study to describe vegetational patterns associated with R. macrophyllum in a western Cascades clearcut.

Mutual Exclusion Between Salmonberry And Douglas-Fir In The Coast Range Of Oregon, Kenneth Ray Still

Dissertations and Theses

One serious problem faced by the forest industry in the Pacific Northwest is poor regeneration of commercial trees on land which is harvested and subsequently dominated by brush species. In Coastal Oregon, salmonberry is one of these brush species. Detailed investigations of field sites indicate that light intensity in the brush stands was low but sufficient for germination and early growth of Douglas-fir seedlings and soil moisture percentages and nutrient levels were high enough to support early Douglas-fir growth. Laboratory tests demonstrated the presence of leachable phytotoxins in the leaves of salmonberry. The hypothesis resulting from this study is that …