Investigating potential determinants of the distribution limits of a savanna woody plant: Colophospermum mopane
Early bioclimatic models predict that climate change in southern African savannas will cause a huge southward and westward range shift of the savanna tree Colophospermum mopane (Kirk ex Benth.) Kirk ex J.Léon. C. mopane is an economically and ecologically important subtropical savanna tree that forms mono-dominant stands across 30% of southern African savannas. We investigate the validity of these initial range expansion predictions to answer the following questions: what are the regional-scale drivers of the distribution of C. mopane in southern African savannas; and what are the landscape-scale distribution patterns of this species?
Central Lowveld, Kruger National Park, South Africa.
We investigate the validity of very early range expansion modelling predictions using a regional-scale, climate envelope niche model, and fine-scale field mapping of the current boundary, to understand which environmental variables may determine the distribution limit of this signature species.
Our findings indicate that both non-climatic (dry season day length) and climatic (minimum temperatures) variables limit the regional distribution of C. mopane. At the landscape scale, the distribution of this species is restricted to the warmer parts of the landscape, suggesting minimum temperature appears to be the primary factor determining its landscape-scale distribution.
This study provides the first detailed model of environmental factors that may limit the regional distribution of C. mopane, and allows us to formulate testable hypotheses regarding the determinants of the range of a keystone species.