HR: 1340h
AN: B43A-0252    [Abstracts]
TI: Soil community structure and ecosystem C cycling in arid ecosystems experiencing multiple environmental changes
AU: * Pavao-Zuckerman, M A
EM: mzucker@email.arizona.edu
AF: University of Arizona, Dept. of Ecology and Evolutionary Biology Biosciences West, 310, Tucson, AZ 85721 United States
AU: Cable, J M
EM: cableje@email.arizona.edu
AF: University of Arizona, Dept. of Ecology and Evolutionary Biology Biosciences West, 310, Tucson, AZ 85721 United States
AU: Huxman, T E
EM: huxman@email.arizona.edu
AF: University of Arizona, Dept. of Ecology and Evolutionary Biology Biosciences West, 310, Tucson, AZ 85721 United States
AU: Scott, R L
EM: rscott@tucson.ars.ag.gov
AF: ARS, USDA, 2000 E Allen Rd., Tucson, AZ 85719 United States
AU: Williams, D G
EM: dgw@uwyo.edu
AF: University of Wyoming, Department of Renewable Resources University of Wyoming, Laramie, WY 82071 United States
AB: Despite the importance of soil carbon cycling to the response of water-limited ecosystems to global change, our understanding of this ecosystem component is still in its infancy. Adding to the complexity in knowledge building, ecosystems are exposed to simultaneous multiple shifts within global change scenarios. For example, semiarid grasslands in southern Arizona are currently undergoing encroachment by woody plants at the same time that climate change models predict increases in frequency and magnitude of precipitation inputs over the next 50 years. We are investigating how heterogeneity of plant cover mediates the response of soil community structure and ecosystem C cycling to seasonal monsoon rain inputs. Field plots were established in a mesquite shrubland in the San Pedro River Basin, AZ that are dominated by either: Sporobulus wrightii, medium sized Prosopis velutina, or large Prosopis velutina, additional plots were located in intercanopy areas. Both increased quantity and quality of litter inputs to the soil component, and physical influences of the shrubs on ecosystem water and energy budgets affects plots influenced by the development of Prosopis. Plant species influenced the response of soil microbial biomass to precipitation pulses. Plant cover also influenced the dynamics of soil nematodes. Magnitude of precipitation inputs and plant cover interact to affect the abundance of trophic group abundances and food web structure. These results will be discussed vis-à-vis the importance of soil organisms for driving ecosystem dynamics, and the appropriateness of dominant paradigms in arid land ecology (notably the pulse-reserve paradigm) for understanding soil components of arid ecosystems. Shifts in soil flora and fauna have important implications for ecosystem C-cycling via alterations of trophic dynamics, and the contribution of heterotrophic respiration to C efflux from ecosystems.
DE: 0428 Carbon cycling (4806)
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
DE: 0486 Soils/pedology (1865)
DE: 0491 Food webs and trophodynamics (4817)
DE: 1632 Land cover change
SC: Biogeosciences [B]
MN: Fall Meeting 2005