Life Sciences Commons^™

Multi-Scale Environmental Conditions Associated With Shade-Tolerant Conifer Regeneration In Forest Park, Portland, Oregon, Matthew Cook

Dissertations and Theses

Forest Park is a 5,100-acre urban forest located in Portland, Oregon, that has been impacted by various anthropogenic stressors including logging, fragmentation, invasive species, air pollution and recreation use due to its proximity to the urban environment. This legacy of land use coupled with natural disturbances has resulted in changes to forest structure, composition, and function--threatening the long-term sustainability of the park. Past research in Forest Park has identified a lack of regenerating shade-tolerant conifers, particularly western hemlock and western red cedar species, in the section of the park closest to the city. Typically, western hemlock and western red cedar …

Tree Canopy Cover And Potential In Portland, Or: A Spatial Analysis Of The Urban Forest And Capacity For Growth, Jeff Ramsey

Dissertations and Theses

Urban forests have positive impacts on human and ecosystem health, reduce stress on aging stormwater infrastructure, increase property values, and reduce energy consumption. The scale of these benefits ranges from the hyper-local to the global. While the benefits of urban forests can extend well beyond the boundaries of cities, they often do not reach all residents of the city equally. Urban forest policies do not adequately address environmental equity or employ planting strategies with knowledge of the social and political factors that determine the spatial variations of tree canopy extent in cities. Chapter I analyzes the determinants of current canopy …

Examination Of Human Impacts On The Biodiversity And Ecology Of Lichen And Moss Communities, Hannah Marie Prather

Dissertations and Theses

Globally, more than half of the world's population is living in urban areas and it is well accepted that human activities (e.g. climate warming, pollution, landscape homogenization) pose a multitude of threats to ecosystems. Largely, human-related impacts on biodiversity will hold consequences for larger ecological processes and research looking into human impacts on sensitive epiphytic lichen and moss communities is an emerging area of research. While seemingly small, lichen and moss communities exist on nearly every terrestrial ecosystem on Earth and contribute to whole-system processes (e.g. hydrology, mineral cycling, food web energetics) worldwide. To further examine human impacts on epiphytic …

Interception In Open-Grown Douglas-Fir (Pseudotsuga Menziesii) Urban Canopy, Mitchell Bixby

Dissertations and Theses

I hypothesized that Douglas-fir trees (Pseudotsuga menziesii) standing apart from other trees ('open-grown') will intercept more rainfall than Douglas-fir trees standing near other trees ('closed-canopy'). Open-grown trees differ structurally and are more common in urban settings, yet have been infrequently studied. Existing literature, based primarily on closed-canopy trees, suggests Douglas-fir trees in Pacific Northwest forests intercept approximately 25% of rainfall annually. Because open-grown trees have more vertical leaf area than individual trees in closed-canopy forests, I expected to find higher interception by open-grown trees.

I collected throughfall under four open-grown Douglas-firs using six static collectors ('buckets') per tree, …