HR: 1340h
AN: B23C-1500    [Abstracts]
TI: Carbon Dioxide and Water Cycling in a Semiarid Savanna in Southern Arizona, USA
AU: * Scott, R L
EM: russ.scott@ars.usda.gov
AF: Southwest Watershed Research Center, USDA-ARS, 2000 E Allen Rd, Tucson, AZ 85719, United States
AU: Hultine, K
EM: hultine@biology.utah.edu
AF: Department of Biology, University of Utah, Salt Lake City, UT 84112, United States
AU: Barron-Gafford, G
EM: gregbg@email.arizona.edu
AF: University of Arizona, Department of Ecology and Evolutionary Biology, Bioscience West, Tucson, AZ 85721, United States
AU: Huxman, T
EM: huxman@email.arizona.edu
AF: University of Arizona, Department of Ecology and Evolutionary Biology, Bioscience West, Tucson, AZ 85721, United States
AB: The consequences of recent woody plant encroachment on the carbon and water cycling of semiarid ecosystems are not well understood. In this presentation, we present measurements made from 2004 - 2006 using sap flow and eddy covariance techniques to examine the carbon dioxide and water fluxes that occurred over a semiarid savanna on the Santa Rita Experimental Range in southern Arizona, USA. Over the last one hundred years this site has been transformed from a desert grassland to a savanna with greater than 35% tree cover by the encroachment of the native woody plant, mesquite ( Prosopis velutina). We have found that mesquite, even when they were dormant above ground, readily redistributed water upwards and downwards in the soil profile via their roots. This redistribution had important ecohydrological consequences like extending the season over which photosynthesis occurred. During the study period the site experienced below normal precipitation especially during the winter and spring period, and the site each year appeared to be a net carbon source. The two decades that preceded our study had above average precipitation, and this possibly resulted in a great deal of carbon accumulation that is now being released due to the current drought that has truncated the growing season.
DE: 1813 Eco-hydrology
DE: 1818 Evapotranspiration
DE: 4806 Carbon cycling (0428)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting