Western spruce budworm defoliated area in the Northern Region has differed significantly across three discrete geographic zones during the past decade. Aerially visible defoliation in northern Idaho increased from 1.7 million acres in 1969 to a high of 2.2 million acres in 1974, and declined to none in 1979. Defoliated...
My thesis explored the effects of and potential mediating mechanisms for an important environmental stressor, ultraviolet-B (UVB) radiation. UVB radiation has negative effects on organisms in both terrestrial and aquatic systems. I used meta-analysis to quantify the effects of UVB radiation on a diversity of aquatic organisms (Chapter 2). UVB...
A parasitic wasp, Trioxys pallidus Haliday
(Hymenoptera: Aphidiidae) was imported from Europe and
initially released against the filbert aphid Mvzocallis
coryli (Goetze) in hazelnut (filbert) orchards of the
Willamette Valley, Oregon beginning in 1984. In the
present study, I investigated the establishment rates of
this parasitoid. A total of 13...
This study examined the effects of Roundup
[N-(phosphonomethyl) glycine] and N-Serve [2-chloro-6-
(trichloromethyl) pyridine] on nitrifying organisms in
static batch, perfusion soil columns, and a new continuous-flow
soil column system. The continuous-flow method is new
to nitrification studies and was shown to produce greater
nitrifier activity than either static batch...
Defensive chemical and nutritive quality of young leaves were measured for 72 individual trees of Chrysolepis [Castanopsis] chrysophylla in conjunction with light intensities of two different stand types and population numbers of Habrodais grunus herri in the Cascade mountains of Oregon. Leaves were collected in the spring and leaf characteristics...
Rivers impacted by human activities often have multiple stressors present. The effects of multiple stressors on biological communities can often be difficult to predict, due to the potential for complex interactions between stressors and communities. This thesis explores the impacts of two stressors often associated with agricultural land use, increased...
Small low-head diversion dams are capable of removing much of the flow of a river, often resulting in increased water temperatures and habitat loss. Warmer temperatures have been shown to accelerate aquatic invertebrate growth and development, and discharge reductions can reduce instream habitat, suggesting that water withdrawals may alter both...
Blueberry production in Oregon is highly reliant upon the ecosystem services of native pollinators, which provide as much as a quarter of the total pollination services received by Blueberry growers. However, the health of these pollinator populations may be affected in yet unforeseen ways as growers adopt new pest management...