WATER-BALANCE IN PURE STAND OF LEHMANN LOVEGRASS

Lehmann lovegrass (Eragrostis lehmanniana Nees), an introduced warm se ason grass, has invaded grasslands in southern Arizona, in many areas replacing the native warm-season grasses. A water balance evaluation i n a pure stand of Lehmann lovegrass showed that more soil water was us ed through evaportranspiration than occurred as precipitation during 2 years of a 3-year study period. During the winter season, an apprecia ble amount of water was used by Lehmann lovegrass or lost by evaporati on from the soil surface. The remaining available soil water was used in the spring dry period. In the dry early spring the soil water conte nts (to depths of 120 cm) were less than the traditional wilting point tension of -1.5 MPa. The invasion of Lehmann lovegrass into grassland s of southern Arizona is partially related to its ability to utilize s oil water during parts of the year when the native species are dormant and also to extract water from the soil profile to very low water con tents.