HR: 09:30h
AN: B51A-06    [PDF]
TI: The Ecohydrological Interactions Between Mesquite and its Water Sources
AU: * Scott, R L
EM: rscott@tucson.ars.ag.gov
AF: USDA-ARS Southwest Watershed Research Center, 2000 E. Allen Rd, Tucson, AZ 85719 United States
AU: Hultine, K
EM: khultine@ag.arizona.edu
AF: University of Arizona, School of Renewable Natural Resources, Tucson, AZ 85721 United States
AU: Ferr\'{e}, P
EM: ty@hwr.arizona.edu
AF: University of Arizona, Department of Hydrology and Water Resources, Tucson, AZ 85721 United States
AB: Velvet mesquite ({\it Prosopis velutina}), a native woody plant to southern Arizona, USA and Sonora, Mexico, has successfully expanded its range and encroached into both upland and riparian grasslands during the 20th century. In this study, we examined the interactions between mesquite and its water sources in order to determine how the trees responded to moisture availability. This study took place in a riparian area and because the trees had access to both deep groundwater and surface water, these interactions resulted in important hydrological and ecological consequences. Surprisingly, we found that the mesquite responded to and even manipulated both surface and deep soil moisture even though they apparently had access to a stable groundwater source throughout the growing season. During dry season nights, observations of root sap flow showed that the trees moved moisture upwards in the taproot and out into the surface soils in lateral roots. As a consequence of this "hydraulic lift", diurnal soil respiration measurements showed that the soil microbes were stimulated following the nocturnal release of moisture into the near-surface regions. During rainy season nights, there was sap flow movement toward the tree in the surface lateral roots and downwards in the taproot indicating "hydraulic descent". Borehole GPR measurements of the deeper, 2 - 10 m, vadose zone moisture content increased apparently as a result of this tree-facilitated water movement. Also, hydraulic descent influenced water table elevations indicating direct groundwater recharge via plant pathways.
DE: 1615 Biogeochemical processes (4805)
DE: 1818 Evapotranspiration
DE: 1851 Plant ecology
DE: 1866 Soil moisture
SC: Biogeosciences [B]
MN: 2003 Fall Meeting