Increasing off-site water yield and grassland bird habitat in Texas through brush treatment practices

Abstract

Woody shrubs, including honey mesquite ( Prosopis glandulosa Torr. var glandulosa) and juniper ( Juniperus ashei Buckholtz and Juniperus pinchotii Sudh), have invaded the native prairies and savannas of much of central Texas. As a consequence of this “brush” encroachment, many of these grasslands may have lost some ability to provide water yield and habitat for some native wildlife species, particularly grassland birds. In some areas, brush management followed by rangeland manipulation treatments may enhance water yields and improve habitat for some grassland-associated wildlife. The relative effectiveness of brush control treatments varies according to the treatment objective and location within a watershed. There are often multiple objectives when public monies are committed for cost-sharing brush management treatments on private lands. When considering multiple objectives (e.g., water yield and grassland bird habitat), the priority ranking process for determining the most cost-effective treatment locations can be confounded. The goal of this study was to reduce this confounding by creating a methodology for prioritizing areas within two watersheds for brush management cost-share programs. We developed a sub-basin scale prioritization method using total society cost of implementing a brush treatment program, hydrologic impacts and grassland bird responses to brush treatments. Results show which sub-basins within the Edwards Aquifer recharge zone and Twin Buttes reservoir watersheds may be the most attractive candidates for brush treatment cost-share programs with the goal of optimizing water yield and grassland bird habitat. By adjusting weights for water and grassland bird efficiency criteria, this approach can be adapted to prioritize different levels of ecosystem responses to brush treatments.