Juniperus virginiana Encroachment Could Limit Herbaceous Vegetation in Central Oklahoma

Abstract

Woody plant encroachment (WPE), the advancement of woody plants into rangelands, threatens rangelands globally and negatively impacts ecosystem services important to humans such as causing losses in cattle production and grassland biodiversity. In the Southern Great Plains, Juniperus virginiana L. has become a pervasive and dominant encroaching woody plant. We examined the effect of J. virginiana on rangeland herbaceous vegetation in central Oklahoma. In 2022, we collected herbaceous vegetation data from J. virginiana-encroached grasslands using a balanced, paired design within J. virginiana-dominated and grass-dominated transects. We analyzed the data using linear or generalized linear mixed models. We found that within J. virginiana-dominated transects there was two times less grass and forb cover than in grass-dominated transects. Within J. virginiana-dominated transects, grass, and forb cover were highest at the edge of the tree. We also detected significant differences in woody cover, green herbaceous cover, and average litter depth between J. virginiana-dominated and grass-dominated transects. These findings align with previous studies that indicate that WPE could limit herbaceous vegetation, which could negatively impact cattle production and pollinators. Reducing woody plant density in rangelands is likely necessary to improve cattle production and pollinator habitat, but the occurrence of woody plants in rangelands can also increase cattle production by buffering temperature extremes. Land managers must determine what their objectives are to determine how to manage WPE appropriately. Utilizing land management strategies that promote multiple ecosystems services such as patch burn grazing could be an important tool to manage woody plants effectively.