Coastal dune topography as a determinant of abiotic conditions and biological community restoration in northern KwaZulu-Natal, South Africa

摘要

Topography is rarely considered as an independentgoal of restoration. However, topography determinesmicroenvironmental conditions and hence livingconditions for species. Restoring topography may thereforebe an important first step in ecological restoration. Weaimed at establishing the relative importance of topographywhere coastal dunes destroyed by mining are rebuilt as partof a rehabilitation program. We assessed the response of(1) microclimatic and soil conditions, and (2) woody plantand millipede species richness and density, to locationspecifictopographic profiles. We enumerated the topographicprofile using variables of dune morphology (aspect,elevation, and gradient) as well as relative position on adune (crest, slope, and valley). Temperature, relativehumidity, and light intensity varied with aspect, elevation,gradient, and position. However, regeneration age was abetter predictor of soil nutrient availability than thesetopographic variables. Age also interacted with topographicvariables to explain tree canopy density and speciesrichness, as well as millipede species richness. Thedensity of keeled millipedes (forest specialists) was bestexplained by topographic variables alone. The transientnature of these new-growth coastal dune forests likelymasks topography-related effects on communities becauseage-related succession (increasing structural complexity)drives the establishment and persistence of biologicalcommunities, not habitat conditions modulated by topography.However, our study has shown that the microhabitats associated with topographic variabilityinfluence specialist species more than generalists.