Location: Range Management Research
Project Number: 3050-21600-001-059-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Mar 1, 2022
End Date: Sep 30, 2025
Objective:
While it is well understood that grazing and drought events affect arid grassland productivity, the effects interactions between drought duration and defoliation frequency are unknown. Long-term experiments suggest that grassland can recover from high levels of defoliation over several years in the context of average precipitation, but intense, multi-year defoliation interacting with multi-year drought may lead to rapid, persistent reductions in productive capacity (known as a "state transition"). The Cooperator will assist ARS in testing the interactions of defoliation frequency/intensity and drought duration in a long-term experiment. The results will be the basis for grazing management guidelines in the context of droughts that are predicted to increase in duration in the coming decades.
Approach:
The Cooperator will collaborate with ARS staff in setting up and running an experiment in six, 0.5 ha paddocks with similar initial grass and shrub cover that will be treated as blocks. Within blocks, treatments will include 3 levels of precipitation reduction, 3 levels of defoliation, and 3 levels of press duration (2, 4, and 8 consecutive years). Grass basal cover and production will be measured prior to July defoliations. Precipitation manipulations will be carried out using a rainout shelter system.
