Influence of some vegetation manipulation practices on the bio-hydrological state of a depleted deep hardland range site
Bedunah, Donald J.
MetadataShow full item record
This study was conducted on the Post Montgomery Ranch, located in the Rolling Plains of Texas. The objectives of this study were three-fold. First, the initial bio-hydrological state of the area was to be evaluated. This evaluation was concerned with the initial rates of infiltration, runoff, sediment loss, and forage production of a depleted range site dominated by mesquite and buffalo grass. Second, the effects of some brush removal methods and types of vegetation manipulation on infiltration, runoff, and sediment rates were to be measured. Third, the study was designed to monitor meterological conditions, vegetation changes, and soil water effects on some hydrological occurrences. The 3 year study was initiated to describe some of the problems associated with decreased productivity and increased aridity of an overgrazed, brush infested range site. The study was designed to measure the rate of improvement in hydrological properties and vegetative condition following different types of vegetation manipulation. Vegetation manipulation treatments consisted of removing mesquite with foliar application of 2,4,5-T + picloram, shredding, mechanical grubbing, mechanical grubbing and vibratilling, seeding to kleingrass, complete removal of all living vegetation, and mechanically forming pits near trees. Infiltration and sediment were determined with a sprinkling-type infiltrometer. Initial soil and vegetation conditions were yery conducive to high runoff and low infiltration. Intense thunderstorms resulted in significant runoff from the area. Water loss from runoff, evaporation, and transpiration from mesquite and reduced vigor of herbaceous plants from long term overgrazing combined to result in yery low herbage production. However, during the study it was evident that the bio-hydrological state of the area was improving. Grass production, grass cover, the amount of herbaceous litter, and infiltration increased each year. Total soil porosity and organic carbon were significantly higher in 1980 than in 1978 or 1979. Sediment yield was 147% greater in 1978 than in 1979 or 1980. Infiltration (cm/hr) for 1980 and 1979 was 320 and 210% higher, respectively, than for 1978. The increased infiltration and decreased sediment was a result of the increased grass production and soil cover. Plant cover protected the soil surface from raindrop impact, and impounded water until infiltration occurred. Each vegetation manipulation treatment resulted in different bio-hydrological responses. However, all mesquite control techniques increased herbage production compared to the check treatment. Infiltration was increased for the shred and vibratill treatments. Vibratilling increased soil roughness and macroporosity allowing rapid infiltration. Shredding mesquite had the immediate effect of reducing mesquite competition for water, returning nutrients to the soil, and the litter helped protect the soil surface from raindrop impact. Vegetation manipulation treatments which caused mechanical soil disturbance decreased runoff from intense thunderstorms. Any available soil water was rapidly used by plants during the growing season. Soil and vegetation variables most highly correlated with infiltration and sediment yield included organic carbon, porosity, herbage production, grass production, above ground herbaceous biomass, grass cover, and total soil cover.