Miranda R. Peterson

MODELING WOODY PLANT ENCROACHMENT IN A SOUTH TEXAS GRASSLAND

Grasslands cover about 40% of the Earth’s land and are vital for wildlife, livestock, carbon and water storage, plant genetic conservation, and other ecosystem services. Despite their importance, grasslands are the most threatened and least protected biome. For over a century, woody plant encroachment (WPE) has increasingly threatened grasslands worldwide, leading to significant impacts on biodiversity and ecosystem services. Woody plant encroachment (WPE) has increasingly endangered grasslands for over a century, impacting biodiversity and ecosystem services. Factors driving WPE include fire suppression, overgrazing, elevated CO2 levels, climate change, and altered hydrology. These factors often interact in complex ways to influence encroachment, and their relative importance remains debated. Simulation modeling is a valuable tool for understanding and addressing WPE, as it allows for the separation, identification, and exploration of influencing factors. Given the global threat of WPE in grassland ecosystems, our goal was to simulate potential future WPE dynamics on the WWR in response to different grazing and prescribed fire schemes under different projected climate change scenarios. To explore WPE dynamics on the WWR, we simulated various grazing and prescribed fire strategies under baseline and future climate scenarios, accounting for moderate and worst-case CO2 emissions. Preliminary results show that heavy stocking rates and summer burns consistently reduce grass biomass. However, heavy stocking rates with winter burns decrease biomass only in current climates, while future climates maintain biomass. This model provides a tool to evaluate grassland management practices in the face of WPE.