Influence of woody dominated rangelands on site hydrology and herbaceous production, Edwards Plateau, Texas

Abstract

Interception of precipitation by blueberry (Juniperus ashei Buchh.) and redberry juniper (Juniperus pinchotii Sudw.) canopies was analyzed using gross precipitation, throughfall, and stemflow data collected at the Texas A&M University Research Station at Sonora, Texas. The objective was to characterize interception by juniper canopy and litter, and to determine the redistributive effects of throughfall and stemflow on site hydrology. Based on a 10-year distribution pattern of rainfall, 66.2% of the precipitation underneath the canopies of J. pinchotii was in the form of throughfall, and 7.9% was in the form of stemflow. Beneath the canopies of J. ashei, 58.2% was in the form of throughfall, while 5. 1 % was in the form of stemflow. 41.6% of the precipitation that fell below the canopies was intercepted by the litter layer of both trees. I The effects that the canopies of both juniper species, and live oak (Quercus virginiana Mill.) have on herbaceous vegetation at various distances from the trunk and the response in herbaceous production following canopy removal were also evaluated. The canopies of all three species reduced herbaceous production. Total standing biomass was greatest at the dripline of all three species. Three years after canopy removal, herbaceous vegetation was bolstered at all sample locations. Hence, the tree species were not only inhibiting herbaceous production beneath the canopies, but also in the tree/shrub interspace as well. Following canopy removal, infiltration rates and sediment production were determined to assess how oak, juniper, bunchgrass, and shortgrass vegetation types and prescribed burning influence rangeland hydrology over time. Woody dominated areas had significantly greater infiltration rates and less sediment production than did grass dominated areas. In addition, following removal, the former oak and juniper mottes retained the hydrological characteristics of woody dominated areas indefinitely. Furthermore, although prescribed burning is an effective, inexpensive means of removing woody vegetation, a cost in the form of accelerated erosion rates was incurred for a brief period after the burn.