Slowing the Expansion of Woodlands and Increasing the Resilience of Grasslands in the Southern Great Plains

What determines the boundaries between grasslands and shrublands or forests is of major scientific interest, particularly since these boundaries can shift over time, sometimes relatively swiftly and seemingly permanently. In large areas of the central and western U.S., woody plants have been spreading into grasslands. Previous research has implicated change in climate and grazing pressure as likely contributing factors. This project extends that work to include effects of governmental policies and social attitudes on the use of fire to keep grasslands open, and to include the impacts of conversion between grassland and woodland on ecological services and resultant economics. Researchers will compare three regions with contrasting degrees of woody encroachment in Kansas, Oklahoma, and Texas to test the hypothesis that changes between grassland and woodland are driven by interactions between fire and grazing regimes that are constrained by policy and culture. The project will provide web-based educational materials, workshops, and tools for private landowners, extension agents, USDA staff, and K-12 science teachers. Results are expected to enhance the scientific basis for maintaining economically valuable grasslands in rural America.

This project will examine the interactions between social and biophysical processes on wildlands in the Southern Great Plains in the context of a novel social-ecological framework. This framework is centered on grassland state changes resulting from woody plant encroachment, and elucidates the socio-ecological properties that emerge when feedbacks, thresholds, and nonlinearities are accounted for. To test the hypothesis that grassland-to-woodland state changes are driven by interactions among fire and grazing regimes that are constrained in space and time by society, policy, and regulations constraining the use of prescribed fire, research will combines empirical biophysical, social, and economic research within a dynamic, iteratively evolving agent-based model (ABM) linked to land cover. This ABM will analyze the factors that influence decision-making by land managers with respect to the use of prescribed fire as a management tool; forecast changes in regional woody plant cover and ecosystem carbon mass under different scenarios of fire use; project the effects of change between grasslands and woodlands on portfolios of ecosystem services including forage production, groundwater recharge, stream flow, and carbon sequestration; and translate changes in ecosystem services into economic metrics.