Mammal burrowing in discrete landscape patches further increases soil and vegetation heterogeneity in an arid environment

Abstract

Burrowing mammal disturbances often create heterogeneity within landscapes. Aardvark (Orycteropus afer) are extensive burrowers in sub-Saharan ecosystems and play an important role in structuring communities in arid environments. The burrowing activities of aardvark are often associated with heuweltjies (nutrient-rich mounds differing in soil and vegetation characteristics from surrounding areas) which contribute strongly to landscape heterogeneity. This study determined the impact of aardvark burrowing and heuweltjies on soil and vegetation characteristics. Data were collected at four microsites: 1) at each burrow entrance on a heuweltjie, 2) on the burrowed heuweltjie (i.e. heuweltjie with an aardvark burrow), 3) on the nearest unburrowed heuweltjie, and 4) on the adjacent matrix. Aardvark burrowing and heuweltjies both impacted the soil and vegetation characteristics. Despite having more moderate thermal regimes than other microsites, burrow entrances were largely unvegetated. Although aardvark burrowing did not affect plant species richness on heuweltjies, it decreased vegetation cover. Vegetation composition differed between heuweltjies and the matrix, and this dissimilarity was increased further by aardvark burrowing. As a result, the combined effect of burrowing mammals and heuweltjies increases landscape heterogeneity. This emphasises the important ecosystem engineering role that aardvark have in arid environments, even where considerable abiotic heterogeneity already exists.