New Mexico Geological Society Annual Spring Meeting — Abstracts

Quantifying water uptake by desert plant roots is highly relevant to groundwater-recharge studies in arid climates. The amount of recharge, or drainage that occurs beyond the zone of evaporation and root absorption, is measureably affected by the extent of vegetation. The consumptive use of water by common desert vegetation has not been quantified to a significant extent by previous investigations.

A field study is being conducted to examine the evapotranspiration of a lavender bush (Dalea scoparia) on a sand dune at the Sevilleta National Wildlife Refuge near Socorro, New Mexico. The bush is isolated from adjacent vegetation and the water table isabout 20 meters be low land surface. The site is equipped with nine neutron access tubes and 36 tensiometers placed on three transects radial to the canopy of the plant. Throughout the study period, March 1985 to April 1986, the soil surrounding the plant was monitored for changes in moisture content and soil-pressure gradients.

A geostatistical model was used to "krige", or predict, the moisture content between observed data points. The moisture-content and pressure-head measurements and meteorological data show that soil-water movement depends on precipitation, evaporation, root transpiration, and topography. The parameters which exert the dominant influence on soil-water movement vary with the season. For example, significant soil-water movement toward the plant occurs in the spring and prior to blossom development. After rain events and dur ing prolonged dry periods, vertical components of soil-water movement dominate.