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Research Project: Brush Management and Ecosystem Services: a Quantification of Trade-offs on Western Rangelands in Support of the LTAR Network

Location: Southwest Watershed Research Center

Project Number: 2022-13610-012-06-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Aug 21, 2015
End Date: Aug 20, 2019

Research sites participating in the Long-Term Agroecosystem Research (LTAR) network are expected to perform a field experiment to compare “business as usual” agricultural management with another management system with the potential to be significantly more productive. For the Walnut Gulch LTAR site, the experiment will focus on brush management due its significant impact on the plant community and widespread application on western rangelands from Arizona east into Texas. Ranchers on Walnut Gulch plan to implement brush management projects, but not on small instrumented watersheds with a history of observations. Consequently, we will perform a complementary study on the four small long-term experimental watersheds on the Santa Rita Experimental Range, which have been monitored for runoff and sediment since 1975. The objective is quantify the effects of brush management on key provisioning, supporting and regulating ecosystem services, to evaluate trade-offs and support more rigorous and holistic evaluation of brush management.

This experiment will complement the work funded in the National Institute of Food and Agriculture (NIFA) proposal “Brush management and ecosystem services: a quantification of trade-offs on Western rangelands” with the University of Arizona as the lead. Task 1: Vegetation will be monitored to quantify forage production, and characterize biodiversity before and after treatment to kill the mesquite to better understand the effects of brush management on mesquite and other species. Task 2: The impact of the change in the plant community on the hydrologic cycle will be assessed by comparison of measured and simulated estimates of components of the hydrologic cycle. Task 3: Field samples of soil and vegetation will be collected and processed for C and N before, one year after, and three years after brush treatment on the 4 small experimental watersheds and eddy covariance tower sampling area to assess the impacts of change in vegetation and the hydrologic cycle on carbon and nitrogen budgets.