ARS | Publication request: THE CONSEQUENCES OF A TWO WATER SOURCE ECOSYSTEM ON THE SURFACE CARBON AND WATER EXCHANGE IN A SEMIARID RIPARIAN WOODLAND 1497

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: December 30, 2002
Publication Date: January 15, 2003
Citation: Scott, R.L., Watts, C., Goodrich, D.C., Martens, D.A., Huxman, T., Lin, G., Hultine, K., Yepez-Gonzalez, E. 2003. The consequences of a two water source ecosystem on the surface carbon and water exchange in a semiarid riparian woodland. American Geophysical Union, Fall Meeting, Dec. 13-17, 2002, San Francisco, CA.

Technical Abstract: A multi-year, multidisciplinary study was conducted to improve our understanding of the carbon and water exchange from a dominant, riparian mesquite (Prosopis velutina) ecosystem. Accordingly, we have used a variety of measurements including above and below-canopy eddy covariance, sap flow, soil/plant respiration, stable isotopes, soil moisture, and water table height to monitor key ecosystem processes and forcing. Groundwater table fluctuations and tree functioning (phenology, carbon uptake, transpiration) were well correlated suggesting that the trees rely principally on this 11 m deep, stable water source. The functioning of the understory plants and soil microbes, however, were dependent on recent precipitation. This bifurcation of water sources between overstory and understory resulted in interesting and unusual ecosystem fluxes. The tree water use was nearly constant before and after the arrival of the summer monsoon whereas the understory functioning changed dramatically. The apparent increase in total ecosystem photosynthesis during the rainy season, however, did not lead to a rise in net ecosystem carbon exchange. Rather, the net uptake of carbon decreased due to the substantial increase in respiration, which was fueled by precipitation, warm nighttime temperatures and an abundant source of deposited tree litter.