OOS 47
Anoxic Microsites in Unsaturated Soils: Drivers of Soil Biogeochemistry, Greenhouse Gas Flux, and Microbial Diversity

Friday, August 15, 2014: 8:00 AM-11:30 AM
202, Sacramento Convention Center
Paul E. Brewer, Colorado State University
Céline Pallud, U.C. Berkeley
Colin Bell, Colorado State University
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.
8:00 AM
 Soil hydration shapes microbial interactions - localized trophic interactions and self-organization of microbial consortia on hydrated soil surfaces
Dani Or, ETH Zurich, Institute of Biogeochemistry and Pollutant Dynamics; Wang Gang, Institute of Terrestrial Ecosystems; Robin Tecon, Institute of Terrestrial Ecosystems
8:20 AM Cancelled
 From the micro- to the nanoscale – studying soil microsites using X-ray spectromicroscopy
Juergen Thieme, Brookhaven National Laboratory; Joerg Prietzel, Technische Universitaet Munich; Mareike Mathes, Univesity of Goettingen
8:40 AM
 Effects of aggregate-scale heterogeneity on selenium immobilization in soil
Céline Pallud, U.C. Berkeley; Matteo Kausch, UC Berkeley
9:00 AM
 Variations in microbial structure and function among soil organic matter aggregates
A. Peyton Smith, University of Wisconsin-Madison; Erika Marín-Spiotta, University of Wisconsin, Madison; Marie-Anne de Graaff, Boise State University; Teri C. Balser, University of Florida-Gainesville
9:20 AM
 Microbial community composition and function in soil aggregates from a fertilized prairie
Kirsten S. Hofmockel, Pacific Northwest National Laboratory; Ryan J. Williams, Iowa State University; Adina Chuang Howe, Argonne National Laboratory
9:40 AM
9:50 AM
 Activity and anoxia: Methanogenesis follows high rates of decomposition in an unsaturated litter patch experiment
Paul E. Brewer, Colorado State University; Joseph C. von Fischer, Colorado State University
10:10 AM
 Non-linear response of soil carbon gas (CO2, CH4) flux to oxygen availability
Gavin McNicol, University of California, Berkeley; Whendee L. Silver, University of California, Berkeley
10:30 AM
 Use of planar O2 and pH optodes in sediment and soils
Morten Larsen, University of Southern Denmark; Ronnie Glud, University of Southern Denmark
10:50 AM
 LandscapeDNDC: Simulation of the redox status for predicting soil-atmosphere GHG exchange
David Kraus, Karlsruhe Institute of Technology (KIT); Klaus Butterbach-Bahl, Karlsruhe Institute of Technology (KIT); Ralf Kiese, Karlsruhe Institute of Technology (KIT); Sebastian Weller, Karlsruhe Institute of Technology (KIT)