Eastward shift in Juniperus virginiana distribution range under future climate conditions in the Southern Great Plains, United States

Eastern redcedar (Juniperus virginiana, redcedar) is a major woody species encroaching upon the native grasslands and forests of the southern Great Plains (SGP), representing a significant threat to regional ecosystem services. Future climate change is anticipated to influence redcedar habitat suitability, changing the probability of further encroachment and reshaping its spatial distribution. In this study, we trained seven Species Distribution Models (SDMs) with redcedar records from the USDA Forest Inventory Analysis database and used the ensemble of these SDMs to simulate redcedar distribution probability under current and future climate conditions in Kansas, Oklahoma, and Texas. Results reveal a distinct east-to-west gradient of decreasing distribution probability in the study domain, primarily driven by climate aridity. Throughout the 21st century, the optimal range of aridity for redcedar habitat is projected to shift eastwards by 0.7 degrees (approximate to 58 km) under the RCP45 climate scenario and 1.3 degrees (approximate to 108 km) under the RCP85. Accordingly, the suitable habitat will shift eastward by 0.6 degrees (approximate to 49 km) in the RCP45 and by 1.2 degrees (approximate to 103 km) in the RCP85. The proportion of unsuitable habitat will increase from 40.2 % of the study domain during 2000 - 2019 to 48 % in the RCP45 and 54.2 % in the RCP85 during 2080 - 2099. Additionally, highly suitable land areas will decrease from 10.4 % of the study domain during 2000 - 2019 to 1.3 % in the RCP45 and 0 % in the RCP85 by the end of this century. This study suggests a low likelihood of further redcedar encroachment in the west of the SGP states under future climates, while anticipating continued expansion in the east, gradually replacing the existing oak forests and rangelands. The findings provide valuable insights for prioritizing WPE management resources and contribute to our understanding of future changes in the SGP vegetation composition and their impacts on ecosystem dynamics.