Characteristics of Oak Mottes, Edwards Plateau, Texas

Abstract

Infiltration of live oak mottes on watershed properties was evaluated in July 1979 at the Sonora Agricultural Research Station. Infiltration rates of undisturbed live oak mottes and those with mulch layers removed were greater than rates of adjacent grass-dominated areas. However, infiltration rates of oak mottes with mulch layer and organic layer removed exposing the mineral were similar to those of adjacent grass-dominated areas. Infiltmtion rates of midgrass-dominated sites were greater than those of shortgrass-dominated sites. Greatest soil loss occurred from oak motte with mineral soil exposed with little differences between other treatments. Infiltration rates and sediment production of oak mottes were most influenced by grass standing crop, mulch and organic layers, soil organic matter, and water stable aggregates. Organic matter and water stable aggregates in the oak motte were similar and significantly greater than in the adjacent grassdominated areas. Surface soil bulk density and texture were similar for the oak mottes and grass-dominated areas. Grass standing crop was similar for the oak motte and midgrassdominated areas but significantly greater than for shortgrass-dominated areas. Mulch accumulation was 6 times greater in oak motte than midgrass areas and 43 times greater than in shortgrass areas. Infiltration, the movement of water into the soil, and soil erosion are modified by the amount and kind of vegetation (Blackburn 1975). Range practices such as brush control and livestock grazing that alter vegetation also have the potential to alter soil surface hydrologic characteristics (Blackburn et al. 1982, Blackburn 1983). Infiltration rates of sagebrush (Arremisiu spp.) canopy zones in Nevada were greater than the adjacent interspace areas (Blackburn