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Universität Regensburg (2008)

Impact of different forms of land use on the vegetation of the Southern Kalahari Duneveld

Horn, Anne

Titre : Impact of different forms of land use on the vegetation of the Southern Kalahari Duneveld

Auteur : Horn, Anne

Université de soutenance : UNIVERSITÄT REGENSBURG

Grade : DOKTORGRADES DER NATURWISSENSCHAFTEN (DR. RER. NAT.) 2008

Résumé
Land degradation in savannas is often associated with overgrazing. This generally results in bush-encroachment, a shift from palatable, large-seeded perennial grasses to less palatable, annual grasses, an increase in bare ground and a decrease in species richness. The causes and processes are not fully understood, although current hypotheses state that stress-adapted, perennial species are more sensitive to disturbance and are replaced by disturbance tolerant species, that profit from the empty space and higher water supply once the cover of perennial grasses has thinned.
In the Southern Kalahari commercial lifestock farms were established in the area from the early to mid 20th century, most of which farm with sheep. Consequently, the vegetation is not only subjected to new disturbances, it also potentially looses mutualistic benefits that have evolved with the indigenous herbivores, such as seed dispersal and associated maintenance of geneflow over large distances.
This study aimed at determining the extent of degradation caused by sheep farming in the Southern Kalahari Duneveld under a range of stocking densities and in increasing distance to the watering point, comparing older and younger farms. Furthermore, the impact of the change of available animal dispersal vectors and their mobility on long-distance dispersal potential and geneflow was determined in an exemplary.

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