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Articles 1 - 5 of 5
Full-Text Articles in Life Sciences
The Conflict Resolution Case Study In Urban Life: Bull Run Watershed Case, Chang-Yu Hong
The Conflict Resolution Case Study In Urban Life: Bull Run Watershed Case, Chang-Yu Hong
Geography Faculty Publications and Presentations
The City of Portland and the United States Department of Agriculture (USDA) Forest Service are working together, along with citizens, to formulate a comprehensive new policy to guide joint management of the Bull Run watershed at Mt. Hood National Forest. This process has brought about four decades of conflict, resulting from differences between the federal view of multiple use and the local view of exclusive use for producing high quality water. The new policy is being formulated by the City of Portland and the Forest Service through negotiation of a comprehensive Memorandum of Understanding that structures the parties’ roles, responsibilities, …
Stream-Associated Amphibian Habitat Assessment In The Portland-Vancouver Metropolitan Region, Andrew Evans Dietrich
Stream-Associated Amphibian Habitat Assessment In The Portland-Vancouver Metropolitan Region, Andrew Evans Dietrich
Dissertations and Theses
This study assessed the influence of landscape development on stream-associated amphibians in forested riparian areas within the Portland-Vancouver metropolitan region. Human alteration of landscapes may dramatically affect the ecology of neighboring aquatic systems. It was hypothesized that lotic amphibians would be negatively associated with greater amounts of landscape development and positively associated with forested area within the surrounding watershed. Thirty-seven 1st-3rd order streams were sampled between June 21st and September 21st in 2011. Streams potentially providing adequate habitat for stream-obligate amphibians were randomly selected. Amphibians were surveyed along 30-meter stream transects using an active-cover search (ACS). Environmental variables associated with …
Direct And Indirect Effects Of An Invasive Planktonic Predator On Pelagic Food Webs, Angela L. Strecker, Beatrix E. Beisner, Shelley E. Arnott, Andrew M. Paterson, Jennifer G. Winter, Ora E. Johannsson, Norman D. Yan
Direct And Indirect Effects Of An Invasive Planktonic Predator On Pelagic Food Webs, Angela L. Strecker, Beatrix E. Beisner, Shelley E. Arnott, Andrew M. Paterson, Jennifer G. Winter, Ora E. Johannsson, Norman D. Yan
Environmental Science and Management Faculty Publications and Presentations
The relative importance of top-down invader effects relative to environmental drivers was determined by sampling crustacean zooplankton, rotifer, and phytoplankton communities in a set of invaded and noninvaded reference lakes. The non-native invertebrate predator Bythotrephes had significant effects on zooplankton community size structure, rotifers, and phytoplankton taxonomic composition, but no significant effects on crustacean zooplankton taxonomic and functional group composition. Part of the variation in phytoplankton communities was explained by the presence of the invader. Because Bythotrephes is generally known to be a carnivore and to not consume phytoplankton, this effect is likely mediated by the zooplankton community’s response to …
Dispersal Limitation And Climate-Related Environmental Gradients Structure Microcrustacean Composition In Freshwater Lakes, Ellesmere Island, Canada, Angela L. Strecker, Rebecca Milne, Shelley E. Arnott
Dispersal Limitation And Climate-Related Environmental Gradients Structure Microcrustacean Composition In Freshwater Lakes, Ellesmere Island, Canada, Angela L. Strecker, Rebecca Milne, Shelley E. Arnott
Environmental Science and Management Faculty Publications and Presentations
Dramatic environmental change is expected in the Arctic, yet little is known about the occurrence and community composition of microcrustaceans in Arctic lakes and how this will be influenced by future environmental change. We sampled and calculated relative abundances of microcrustacean species in 54 lakes on Ellesmere Island, Canada. New species records on Ellesmere Island included Daphnia umbra, Tachidius discipes, and Artemeopsis stefanssoni. Daphnia middendorffiana/tenebrosa was the most common taxon and often dominated microcrustacean assemblages, likely a result of its pigmentation, which offers resistance to ultraviolet radiation. Species richness was positively associated with nutrients, dissolved organic carbon (DOC), temperature, calcium, …
Impact Of Bythotrephes Invasion On Zooplankton Communities In Acid-Damaged And Recovered Lakes On The Boreal Shield, Angela L. Strecker, Shelley E. Arnott
Impact Of Bythotrephes Invasion On Zooplankton Communities In Acid-Damaged And Recovered Lakes On The Boreal Shield, Angela L. Strecker, Shelley E. Arnott
Environmental Science and Management Faculty Publications and Presentations
Invasive species introductions into freshwater ecosystems have had a multitude of effects on aquatic communities. Few studies, however, have directly compared the impact of an invader on communities with contrasting structure. Historically high levels and subsequent reductions of acid deposition have produced landscapes of lakes of varying acidity and zooplankton communitystructure. We conducted a 30-day enclosure experiment in Killarney Provincial Park, Ontario, Canada, to test the effects ofBythotrephes longimanus, an invasive invertebrate predator, on two contrasting zooplankton communities at different stages of recovery from acidification: recovered and acid damaged. Bythotrephes significantly decreased zooplankton biomass and abundance in both communities but …