Termite mounds alter the spatial distribution of African savanna tree species

Aim: Termite mounds form small islands of enhanced water and soil nutrient availability on otherwise dry and nutrient-poor hill crests, which can have important impacts on the plant community. However, the way in which termite mounds alter the spatial distribution of particular tree species across broad savanna landscapes is poorly understood. We aimed to understand the nature and extent of the relationship between termite mounds and key woody savanna species at landscape scales through the use of airborne remote sensing. Location: Kruger National Park, South Africa. Methods: We mapped 9894 termite mounds and 666,679 savanna trees from 15 species across two landscapes with contrasting rainfall regimes using airborne imaging spectroscopy and LiDAR data. We then examined changes in tree species densities and community composition with respect to distance from termite mounds. Results: In both landscapes, termite mounds reduced overall tree densities over distances up to 10 m from mound centres. However, the effect of termite mounds on tree density differed among species, with some species, typically associated with lowland and riparian habitats, showing increased density near termite mounds. Indeed, changes in overall tree community composition revealed that termite mounds harbour tree communities similar to lowland communities, with this similarity decreasing with increased distance from the nearest mound. Termite effects were more pronounced in the savanna landscape receiving higher annual rainfall, whereas a greater percentage of the landscape was affected in the drier landscape due to higher mound densities. Main conclusions: Termite mounds mediate the spatial distribution of tree species in savanna landscapes, increasing the abundance of tree species typically associated with lowland habitats. This contributes to the spatial heterogeneity of savanna vegetation within landscapes and the maintenance of savanna biodiversity.