Hydrologic impacts of mechanical shearing of Ashe juniper in Coryell County, Texas



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Texas A&M University


Several studies have been conducted to research the effectiveness of brush removal on hydrologic properties such as increased water yields and water quality. The Leon River Restoration Project (LRRP) is a large scale brush management program aimed at assessing the impacts of the mechanical removal of Ashe juniper (Juniperus ashei) on the quantity and quality of water, as well as wildlife habitat and livestock forage production. The objectives of this particular study are to assess the short and long term impacts of mechanical rangeland management techniques on runoff water yield and sediment loss from rainfall simulator plots. Two ecological sites were used to conduct rainfall simulation in 3 stages. Rainfall simulations were completed on Redland and Low Stony Hill sites in June 2003 prior to treatment, July 2003 after Ashe juniper was sheared from treated areas of both sites and 11 months after treatment in June 2004. Infiltration rates on both the Redland and Low Stony Hill sites increased after juniper was removed except for the treated brush plots on the Redland site, which experienced a 33% decrease. During the third simulation, infiltration rates decreased on all plots. Grass and litter biomass, as well as bare ground were influential on both sites. Percent bare ground affected infiltration rates the most on the Redland site where bare ground on the treated brush site was 23% in July 2003 and 42% in June 2004. The grass plots on the Low Stony Hill site had the greatest percentages of bare ground during the second simulation. Very few significant differences were apparent with sediment production on the Low Stony Hill site; however, the treated brush plots on the Redland site did experience a significant increase in soil loss following treatment. Sediment production increased from 24.6 kg/ha to 1,730 kg/ha in one month on the treated brush site. All other plots on the Redland site decreased in sediment discharge. Sediment production also had minor increases on the grass plots and treated brush of the Low Stony Hill. Once again, standing crop and bare ground seemed to have the greatest influence on sediment production.