| In the last several decades research into soil respiration has accelerated dramatically, largely because of growing concern about the role of ecosystem CO2 emissions in driving climate change. Soil carbon (C) is the largest terrestrial pool of actively cycling C, such that any response of soil respiration to warming may form a positive feedback on climate change. By and large, most studies of soil respiration focus on growing season processes. In this dissertation, I address this knowledge gap by studying soil respiration in a set of winter-dominated ecosystems in southeast Wyoming, with a central focus of understanding controls on winter soil respiration. The unifying question is "How does winter soil respiration in seasonally snow-covered systems respond to a changing environment?" In this dissertation, I separately quantify autotrophic (roots and rhizosphere) and heterotrophic (decomposer microbes) soil respiration, and then analyze the controls on soil respiration. In particular, I focus on the of soil respiration to physical drivers such temperature, snow and soil water, and biotic drivers such as microbial biomass, substrate use dynamics, and root biomass. The overarching result is that while physical drivers may explain a substantial amount of the variation in soil respiration, biotic drivers must be included in any careful analysis of soil respiration. Variable snow depth is a critical driver of winter soil respiration due to its influence on soil temperature and water availability. However, soil organisms can acclimate to soil conditions, such that the response of soil respiration to changing snow depth and soil temperatures are probably not predictable from simple physical and empirical models. |
