HR: 0800h
AN: B51A-0932    [Abstracts]
TI: Evaporation rates of pasture-mesquite vegetation in central Mexico
AU: Sosa, E G
EM: egs@uaq.mx
AF: University of Queretaro. School Enegineering, University of Queretaro.CU Cerro de las Campanas S/N. Centro., Queretaro, Qro 76000 Mexico
AU: * Escobar, A G
EM: guevara@uaq.mx
AF: University of Queretaro. School Enegineering, University of Queretaro.CU Cerro de las Campanas S/N. Centro., Queretaro, Qro 76000 Mexico
AB: The semiarid highlands of Queretaro, in central Mexico, are characterized by booming urban and industrial developments with increasing demand for water. Agriculture takes place in the valleys and the surrounding hills have different types of xeric to subtropical rangeland. Hills are unfit for agriculture and usually are managed for cattle production and fuelwood. However, recent studies suggest that some hill areas are important for groundwater recharge and if they are not protected, important water shortages are envisioned. A critical question involves the effects of land management practices on rangeland hydrologic processes. Evaporation (E), which includes plant and soil evaporation is the largest water loss from rangelands and few data are available for central Mexico. The objective of this study was to estimate E from a mesquite (Prosopis sp.) dominated vegetation using the eddy correlation and the Pennman-Monteith models. Measurements were made during 24 summer days of 2004 at a piedmont site at Amascala, Queretaro (1919 m, 20ø 41' N, 100ø 16' W). Long term annual rainfall is 568 ñ 137 mm. Shrub density was 770 plants per hectare and mean height was 1.8 m. The understory was composed by a mixture of annual and perennial grasses but their biomass was negligible. Agroforestry was the current land use of the site. Shrubs were pruned every 2 or 3 years to maintain its height and promote leafty regrowth. Goats usually browsed the mesquite canopy, but during the time of the study they were excluded from the area.The rainy season started on 15 May and measurements initiated on 1 June, five days after a severe hail storm. Although the mesquite canopy had a full developed canopy with leaf area index of 3.2 by this time, they lost approximately 70% of leaf area. May and June rainfall was 146 mm and 46 mm occurred during the measuring period. Throughout the measurement period E was coupled to global radiation and total evaporation was 73.8 mm. On cloudy days E ranged from 1.1 to 2.0 mm d-1, maximum E was 4.3 mm d-1 on sunny days and the average E was 3.1 mm d-1. Average daily E increased during the measuring period at a rate of 0.05 mm d-1 (r2=0.2, p<0.05). Data suggest that evaporation from a pasture-mesquite vegetation is an important component in the water balance considering the limited rainfall occurring.
DE: 1818 Evapotranspiration
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting