PARENT SESSION
Wednesday, August 9, 8:00-11:30 am
COS 56 - Soil ecology
Mississippi, Mezzanine Level, Cook Convention Center
Presiders: S Baer and J Six
Abiotic and biotic controls on soil organism activity in semi-arid ecosystems.
Pavao-Zuckerman, Mitchell*,1, Huxman, Travis1, Pierce, Nathan1, Cable, Jessica1, Scott, Russell2, Williams, David3, Eilts, Alex1, 1 University of Arizona, Tucson, AZ2 USDA, ARS, Tucson, AZ3 University of Wyoming, Laramie, WY
ABSTRACT- The composition and activity of soil communities are primary drivers of material and energy transformation and exchanges in terrestrial ecosystems. Despite their importance in understanding how ecosystems may respond to global change, there is a dearth of information concerning soil organisms in arid ecosystems. We present the results of two experiments conducted in southeastern Arizona that were designed to (1) mechanistically deconstruct the abiotic and biotic controls on the activity and composition of soil floral and faunal communities, and (2) elucidate their role in ecosystem fluxes of C and N. In the first study, we manipulated the frequency and magnitude of precipitation inputs to grassland plots, and extracted nematodes from rhizosphere and bulk soils. While the abundance of nematodes in rhizosphere soils did not differ between plots that received no and multiple watering, nematodes were most abundant in bulk soil that had multiple and relatively large watering treatments. In a second study, we are investigating the influence of plant cover type (bunchgrasses, small, medium, large, and dead woody plants) on soil properties, including, microbial and nematode community composition, microbial substrate utilization, and soil CO2 flux, and N mineralization. Water and nitrogen additions are used to further deconstruct the environmental effects of plant cover type. These studies indicate that in arid systems, soil organism activity is primarily controlled by water availability, and secondarily by soil organic matter and N contents. In addition, plant functional type influences soil communities by affecting soil microclima
Key words: soil respiration, soil ecology, semi-arid savannah