Seasonal Use of Soil Water by Mature Velvet Mesquite

Abstract

Mesquites used water consistently to a depth of 3 m and outward to 10 m beyond the crowns, but use at 15 m was limited mainly to drier periods when water supplies closer to the trees were depleted. With the start of spring growth, water was extracted most rapidly from the surface layers. As the season advanced, the watersupply zone became increasingly thicker. Rates of extraction were highest immediately after recharge in early spring and early summer, and lowest in late fall. Differences in available water in the soil accounted for 72 to 88% of the variation in rates of extraction. The competitive effect of velvet mesquite on perennial grasses is most severe in the upper 37.5 cm of soil under and near the mesquite crowns, and gradually decreases with distance into adjacent openings. The competitive effect in the openings is much more severe in dry years than in wet years.