Abstract:
The impacts of ecosystem engineers may be expected to vary along environmental gradients. Due
to some resources being more limited in arid than in mesic environments, disturbances created by
burrowing mammals are expected to have a greater ameliorating effect in arid environments, with
larger differences in microhabitat conditions expected between burrows and undisturbed areas. The
aim of this study was to test if the impacts of a medium-sized burrowing mammal, the aardvark, on soil
properties (soil temperature, moisture and compaction) and vegetation characteristics (plant cover,
species richness and species composition) are consistent across three biomes that differ strongly in
annual rainfall. Burrowing affected soil and vegetation attributes, but the direction and magnitude
of these biogeomorphological impacts were not consistent across the different biomes. For example,
plant species composition was altered by burrowing in the arid scrubland and in the mesic grassland,
but not in the semi-arid savannah. Contrary to expectations, the difference in the impacts of burrowing
between biomes were not related to rainfall, with burrowing having strong, albeit different, impacts
in both the arid scrubland and the mesic grassland, but weaker effects in the semi-arid savannah. It
appears, therefore, that the impacts of these biogeomorphic agents may be site-specific and that it may
be difficult to predict variation in their biotic and abiotic effects across environmental gradients. As a
result, forecasting the impacts of ecosystem engineers under different conditions remains a challenge
to management, restoration and conservation strategies related to these types of species.
