IRRIGATION EFFECTS ON GROWTH AND WATER-USE OF QUERCUS-VIRGINIANA (MILL) ON A TEXAS LIGNITE SURFACE-MINED SITE

Three different irrigation regimes (100%-high, 67%-medium and 33%-low of estimated well-watered conditions) were applied to Quercus virginia na (live oak) seedlings on reclaimed lignite surface-mined soils in ce ntral Texas as a means to study the physiology and growth of seedlings during establishment. The study period was 4 July 1990 through 30 Sep tember 1990. Transpiration, stomatal conductance and water potential w ere significantly higher (alpha=0.05) in the high treatment than in th e low and medium treatments. Favorable water status contributed to som ewhat greater seedling growth in the high treatment than in the low an d medium treatments. Greater growth was associated with favorable seed ling water potential, high stomatal conductance and rapid transpiratio n in the high treatment. Physiological responses and growth characteri stics indicated that an irrigation rate of 1.2 kg.d-1 per seedling dur ing the dry summer months was sufficient for seedling survival and est ablishment. An irrigation rate of 3.8 kg-d-1 per seedling promoted rap id seedling growth in addition to ensuring establishment.