ES-06. The Changing Sulfur Cycle: Effects and consequences of human-impacted sulfur cycling

Abstract
Humans have greatly perturbed the biogeochemical sulfur (S) cycle, primarily through the liberation of geologic S faster than the return of S back into these forms. As a result, the amount of bioavailable S cycling through the biosphere has more than doubled since pre-industrial times. Bioavailable S is released into the biosphere through industrial emissions, agricultural additions, and increased rock weathering from climate change. My work examines environments affected by high S concentrations and seeks to quantify S cycling processes in these areas. Firstly, I present my work from the Niwot Ridge Long Term Ecological Research Site. Alpine areas have experienced increasing stream sulfate export under a warming climate. My work shows that wetter areas on the alpine landscape may be key hotspots for sulfate reduction activity. Next, I present work from Napa Valley, California, where S applications to vineyards causes elevated export of S from fields to downstream areas. My data show how sulfate reduction activity changes across the Napa Valley watershed in relation to sources of agricultural S. Finally, my future and ongoing work compares my current data with vineyard sites in New Zealand, and examines the soil microbial communities across California, Niwot, and New Zealand sites. Altogether, my research is yielding new understanding of how human influences on the S cycle are affecting S cycling processes and the microbial communities responsible for these processes.