dissertationSnow cover directly influences soil temperature (Tsoil) and water content (θ), two primary drivers of ecosystem processes such as primary production and soil biogeochemical cycling. Variations in seasonal snowpack size, duration, and other characteristics therefore have the potential to significantly impact ecosystem structure and function. In the mountain ranges of the interior western United States, a region with abundant snowfall and complex topography, there is great temporal and spatial variability in snowpack characteristics. Interactions between snow and ecosystems are poorly quantified here, and with significant hydroclimatic (and snowpack) change occurring in the western U.S., it is increasingly critical to understand how this regional snowpack variability influences ecosystem structure and function. In three complementary research projects I tested the hypothesis that seasonal snowpack characteristics influence ecohydrological and biogeochemical processes in the montane ecosystems of this region. Using data from a large network of automated snowpack monitoring stations (252 sites), I quantified interannual and spatial patterns in Tsoil and θ, and their dependence on regional snowpack variation over an 11 year period. Below-snowpack and warm season Tsoil and θ were significantly related to snowpack size, melt date, and early season snow accumulation. In a 3-year manipulative experiment I compared the impacts of aeolian dust deposition, canopy structure, and interannual snowfall variability on snowpack ablation and ecosystem processes in a subalpine conifer forest. Canopy structure had a larger impact (through interception and shading) on snow accumulation and ablation than dust addition treatments. Dust and canopy structure effects on Tsoil, θ, and ecosystem processes were small compared to the effects of interannual variability in snowpack size and melt timing. In a study of 21 conifer forests in the Wasatch and Uinta ranges of Utah, I tested whether climatic drivers, including snowpack characteristics, explained spatial patterns in soil and detrital organic matter stock size and isotopic composition (13C and 15N). The climate of these sites explained only a small portion of variability in stock sizes and isotope ratios, suggesting that site-specific factors (disturbance, species, soil texture) are predominant controllers of the production and decomposition of forest organic matter stocks
