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Title Mechanisms of vegetation change: ecological transition zones sensitive to global change in South and West Africa

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Short title Mechanisms of vegetation change at ecological transition zones

Author(s) Shiponeni, N.(1); Goetze, D.(2); Hennenberg, K.J.(2); Kersting, P.(3); Allsopp, N.(4); Carrick, P.J.(1); Porembski, S.(2); Hoffman, M.T.(1)

Presenting author Ndafuda Shiponeni

Institution(s) (1) Department of Botany, University of Cape Town; (2) Institute of Biosciences/Botany, University of Rostock; (3) Geographical Institute, University of Mainz; (4) ARC-Livestock Business Division, Bellville

Keywords Ecotone; grassland–woody vegetation mosaic; vegetation dynamics; vegetation patches; water availability

Abstract Over vast areas of South and West Africa, grassland and woody vegetation occurs in close proximity. In ecological transition zones along subcontinental moisture gradients both vegetation forms co-exist forming patchy vegetation mosaics. Detailed knowledge on their properties and dynamics was gained in order to elucidate ecosystem functioning and predict future developments. Under constant geological, moisture and land use conditions soil properties do not primarily account for the vegetation patterns. Instead, water availability patterns in space and time appear to be a key factor. In the South African Succulent Karoo and Nama-Karoo winter or summer rainfall favours either succulent shrubs or grasses. In their transition direct competition for water resources appears to determine the local pattern of both vegetation types. In the Guineo-Sudanian forest–savanna mosaic of West Africa, water availability on the gently undulating relief is higher in hollows and decreases toward hilltops. Production of combustible grass biomass decreases accordingly toward the hilltops, leading to less intense anthropogenic fires and a greater chance of woody species to establish on hilltops that shade out grasses and keep out fires themselves. In both regions, the above-mentioned processes provoke a stabilization of the vegetation pattern. Modelling of climate and land use changes allows for recommending sustainable management.

Congress Topic Process Analysis

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