Under conditions of fixed N-limitation, as with most oligotrophic systems, the process of biological N₂ fixation (diazotrophy) is favored, provided the necessary trace elements and vitamins are sufficient. Despite the well understood contributions of N₂
fixation in oligotrophic regions, the nutritional and ecological controls of marine diazotrophs have not been...
In a steady state, the Earth's absorbed solar radiation (ASR) balances the outgoing
longwave radiation (OLR) at the top of the atmosphere (TOA). In response to a radiative
forcing, that is, an external perturbation to the top of the atmosphere energy balance, the
Earth's climate system adjusts until reaching a...
Emerging infectious diseases in wild animals threaten global biodiversity as well as domestic animal and human health. Their unprecedented increase in conjunction with anthropogenically induced range shifts of endemic pathogens exposes hosts to novel parasite combinations, lending urgency to research on disease dynamics in wildlife systems. In natural populations, hosts...
There is a growing consensus that anthropogenic warming will impact soil organic matter (SOM). Globally, soil contains 2-3 times more carbon (C) than plants, and like plants, temperature induced change of SOM could have significant climate repercussions. Although, the majority of warming experiments have increased day and night temperatures equally,...
Soil properties may hold the key to improved predictions of soils during digital soil mapping (DSM), which has developed with a focus on environmental factors external to soil. The spatial variability in soil properties was modeled across Malheur National Forest in eastern Oregon as an approach to improve DSM. The...
Stream discharge is a key water balance component and important factor in global change evaluations. Nevertheless, the mechanisms for streamflow generation are poorly understood. Near- stream surface saturation during precipitation events is one of the most iconic, visible indicators of rapid runoff production in upland humid catchments around the world....
Ocean circulation is an important component in Earth's climate system. Predicting future climate and circulation changes requires an improved understanding of the past relationship between climate and ocean currents. The neodymium isotope composition (εNd) of water masses is frequently used as a quasi-conservative tracer to reconstruct ocean circulation. The current...
The research presented in this thesis seeks to further our understanding of the geochemical signatures that can be used to trace and quantify non-ferrous smelting emission inputs into the environment. Strong evidence suggests that emissions from the non-ferrous smelter in Trail, BC are the primary source of metals deposited from...
This dissertation reports on four related, though separate projects. The first project details the process of carrying out a digitally augmented soil mapping (DSM) effort alongside an ongoing survey in Oregon's Ochoco National Forest (ONF) using a Random Forest algorithm. The second chapter describes a initial soil survey in Oregon's...
Soil nitrogen exists largely as organic matter, including plant liter, dead animal matter, and microbial necromass. About 90% of soil organic nitrogen is proteinaceous material that is too large for plants and microorganisms to assimilate directly. Protein depolymerization therefore plays a critical role in mobilizing this organic source of nitrogen,...