HR: 16:35h
AN: H44C-03    [Abstracts]
TI: Regional Trends in Streamflow in Central Texas: Reconciling the Effects of Degradation and Woody Plant Encroachment
AU: * Wilcox, B P
EM: bwilcox@tamu.edu
AF: Ecosystem Science and Management, Texas A&M University, College Station, TX 77843, United States
AU: Huang, Y
EM: yhuang@lbg-guyton.com
AF: Ecosystem Science and Management, Texas A&M University, College Station, TX 77843, United States
AU: Perotto, H
EM: hperotto@tamu.edu
AF: Ecosystem Science and Management, Texas A&M University, College Station, TX 77843, United States
AB: The extent and density of woodlands and shrublands have expanded greatly on drylands across the globe—a phenomena described as woody plant encroachment. Rangelands in Texas for example have been largely converted from grasslands and savannas to woodlands in the last 150 years. In Central Texas—a landscape with a predominantly karst geology—Ashe juniper and oak have come to dominate much of the landscape. These changes were set in motion by the severe overgrazing that occurred at the turn of the last century. The vegetation has transitioned from healthy savanna to degraded grasslands and now finally to woodlands. The hydrological consequences of this conversion have been evaluated from the plot to the small catchment scale using a variety of techniques. The general consensus from this body of work is that recharge and streamflow are around 50 mm lower when woody cover predominates. One would expect then that long terms trends in streamflow would reflect a declining trend as woody plant coverage has progressively increased in the last century. Surprisingly, however, we find no declining trends in regional streamflow during the period of record (around 80-100 years) and in fact there are indications that the baseflow component of streamflow has increased slightly during this time. We propose that these counterintuitive results (increasing streamflow with conversion from degraded grasslands to woodland) are the result of a general improvement in rangeland condition that has occurred in the last 50 years or so.
DE: 1813 Eco-hydrology
DE: 1834 Human impacts
DE: 1860 Streamflow
DE: 1879 Watershed
SC: Hydrology [H]
MN: 2007 Fall Meeting