99th ESA Annual Meeting (August 10 -- 15, 2014)

OOS 47

Anoxic Microsites in Unsaturated Soils: Drivers of Soil Biogeochemistry, Greenhouse Gas Flux, and Microbial Diversity

Small-scale (μm-cm) redox heterogeneity within unsaturated soils, and the consequent formation of anoxic microsites, has recently been shown to contribute to greenhouse gas flux, heavy-metal mobility, nutrient cycling, and microbial community structure. Such redox structures provide substrates and conditions necessary for a much wider range of reactions than would be found in a soil with uniform redox conditions – creating the potential for an underground network of vast interfaces where unexpected chemical and metabolic functions occur. Pioneering work that established the importance of anoxic microsites for denitrification and N2O flux in upland soils has been followed by environmental quality and microbial ecology studies that highlight the role of anoxic microsites in stabilizing contaminants in soil and shaping microbial diversity. There is also mounting interest in investigating the effects of small-scale soil structures on soil communities and their function. This session spans many ecological disciplines due to the wide-ranging effects of redox heterogeneity and the paradigm-challenging nature of the subject. There are presentations appealing to biogeochemists, microbial ecologists, ecosystem ecologists, plant and rhizosphere researchers, climatologists, soil chemists, and those interested in environmental quality. We have invited speakers from across this wide range and they span positions from graduate students to established faculty. The first half of the session focuses on the relationship between physical soil structures and microbial communities, building up from the nano-scale to the aggregate scale. The second half focuses on the causes of redox structure (low diffusion or high consumption of oxygen) and the effects on greenhouse gas flux. Throughout the session we feature a mixure of experimental work, models, and new tools to show how current empirical work informs theory and what new paths have been illuminated for future experiments.