Exploring environmental factors that influence the distribution of poplar trees

Abstract

Poplar is an invasive alien plant (IAP) that encroaches on fragile landscapes in South Africa, but the environmental factors that contribute to its spread are not well understood. To address this gap, we conducted a study using generalised linear models (GLM) to identify the most significant local environmental factors that drive poplar establishment and dispersion in Golden Gate Highlands National Park (GGHNP). We then ranked these variables according to their contribution to poplar occurrence using a random forests regression approach. Our GLM analysis revealed that soil properties such as soil organic carbon, sand and silt, topographical variables such as aspect and slope, normalised difference moisture index (NDMI) and poplar distance from rivers are significant factors affecting poplar survival. After ranking the variables, we found that the three most important factors influencing poplar occurrence were aspect, slope and poplar distance to rivers, followed by the sand, silt, NDMI, and soil organic carbon. Our results are consistent with previous studies, indicating that topographical variables and the availability of sufficient water supply are the primary drivers of the spread of IAPs. This study provides useful insights in managing and monitoring poplars in delicate landscapes.