Abstract:
Termite mounds contribute to the spatial heterogeneity of ecological processes in many savannas, but the underlying
patterns and determinants of mound distributions remain poorly understood. Using the Carnegie Airborne Observatory
(CAO), we mapped the distribution of termite mounds across a rainfall gradient within a river catchment ( ∼ 27 000 ha)
of the Kruger National Park, South Africa. We assessed how diff erent factors were associated with the distribution
and height of termite mounds at three spatial scales: the entire catchment, among three broad vegetation types, and
on individual hillslope crests. Abiotic factors such as the underlying geology and mean annual precipitation shaped
mound densities at broad scales, while local hillslope morphology strongly infl uenced mound distribution at fi ner
scales, emphasising the importance of spatial scale when assessing mound densities. Fire return period had no apparent
association with mound densities or height. Mound density averaged 0.46 mounds ha 1 , and exhibited a clustered
pattern throughout the landscape, occurring at relatively high densities (up to 2 mounds ha 1 ) on crests, which are
nutrient-poor elements of the landscape. Mounds exhibited signifi cant over-dispersion (even spacing) at scales below
60 m so that evenly spaced aggregations of termite mounds are embedded within a landscape of varying mound
densities. Th e tallest mounds were found in dry savanna (500 mm yr 1 ) and were positively correlated with mound
density, suggesting that dry granitic savannas are ideal habitat for mound-building termites. Mound activity status
also varied signifi cantly across the rainfall gradient, with a higher proportion of active (live) mounds in the drier sites.
Th e diff erential spacing of mounds across landscapes provides essential nutrient hotspots in crest locations, potentially
sustaining species that would otherwise not persist. Th e contribution to biodiversity and ecosystem functioning that
mounds provide is not uniform throughout landscapes, but varies considerably with spatial scale and context.
