Vegetation distribution along a granite catena, southern Kruger National Park, South Africa

Abstract

This study aimed to investigate how environmental factors drive the assemblage of vegetation within a landscape at various scales, particularly to which extent a sequence of soil forms (catena) influences plant community distribution in a savanna of Kruger National Park, South Africa. On a regional scale, the geology and associated soil forms correspond to the Granite Lowveld Vegetation Type. These associations were studied at the scale of a single hillslope, comprising concurrent soil and vegetation surveys from the crest to footslopes. From chemical and physical soil analyses, strong correlations between the distribution of soil moisture content, soil forms and plant species at community, sub-community and variant levels were found. A Vachellia exuvialis–Pogonarthria squarrosa-dominated savanna is restricted to the well-drained, nutrient-poor, acidic and sandy soils of the crests and upper-midslopes of the granite domes. On sodic sites along lower-midslopes, Dactyloctenium aegyptium–Sporobolus nitens grasslands dominate the clay-rich soils. The footslopes are characterised by the grass Themeda triandra and the shrub Flueggea virosa. The grass Panicum maximum growing under tall trees such as Diospyros mespiliformis and Spirostachys africana typifies riparian vegetation along seasonal streams on deep alluvial soil. The association between plant communities and soil forms exemplifies the interdependency of biotic and abiotic components that maintain heterogeneity within the ecosystem from biome to community scale.

Conservation implications: This article contributes to understanding plant species distribution along a granite catena; an integral part of which are sodic sites that become overutilized by game, which, albeit natural, could severely impact these sites during drought situations.