Arbuscular mycorrhizal fungi (AMF) may exert profound influences on ecosystem resilience and invasion resistance in western North American sagebrush steppe and other arid rangeland plant communities. Maintenance of plant community structure through ecological feedbacks such as facilitation of nutrient cycling and uptake by host plants, physical and chemical contributions to...
The rare earth elements (REEs) have been established as powerful tracers for a range of physiochemical processes occurring in the natural environment. They also hold significant economic importance as many technological advancements are reliant upon the REEs for their unique magnetic, luminescent, and electrochemical characteristics. In sedimentary settings, understanding the...
Since the late 1880's western juniper has expanded in range and
increased in density in sagebrush-bunchgrass, riparian, and forested plant
communities of the Pacific Northwest. Succession to western juniper
woodland has been shown to reduce the productivity and diversity of the
understory component, result in concentration of soil nutrients beneath...
A method was developed for assessing the vulnerability
of groundwater to contamination from contaminant sources
at the soil surface, using a numerical groundwater flow
model linked to a digital map database. The method was
applied using the pcARC/INFO Geographic Information System
(GIS) to input, store, and manipulate base maps, resulting...
Low-permeability geologic units may offer significant chemical and hydraulic protection of adjacent aquifers, and are important for managing groundwater quality, especially in areas with significant non-point source contamination. Nitrate in the Willamette Valley is attenuated across the Willamette Silt, a semi-confining unit overlying a regionally important aquifer. To quantify the...
To determine whether shading increases drought-induced
root mortality by changing the chemical
composition of roots, I conducted an experiment in which
high and low light treatments in combination with high
and low soil moisture treatments were applied to
seedlings of Douglas-fir (Pseudotsuqa menziesii Mirb.
Franco). Because synthesis of suberin (a...
Most soil organic C is in a stable form, associated with clay minerals in the upper soil profile. Upon environmental and land-use changes, stable soil C is subject to losses, which influence the global C cycle and the productivity of terrestrial ecosystems. However, mechanisms controlling soil C destabilization are not...