| Abstract |
Rangelands in arid areas of southern Africa are prone to degradation through overutilization. Once degraded, rangelands recover very slowly or may not recover without external drivers such as very high-rainfall years. To what extent, at what pace, and to which state Succulent Karoo vegetation is able to recover from long-term exposure to high grazing pressure ? from extensive commercial farming, for instance ? is poorly understood. We analysed 17 years of annual vegetation monitoring data from the Hardeveld bioregion of the South African Namaqualand. Th e recording commenced one year aft er the grazing pressure on the rangeland had been reduced from as much as 120% to 30% of the recommended stocking rate. Non-metric multidimensional scaling (NMDS) of all 17 annual relevés for the 20 plots showed a strong division of the species composition into 8 upland and 12 lowland plots. When applying NMDS to the relevés for the plots separately, in comparison with the lowland plots, upland plots showed a stronger directional change where the species composition shift ed away from the initial state. Th e year-to-year species turnover per habitat, however, was greater on lowland compared to upland habitats. Th e visualisation of the cover changes per life form type showed that both habitats differed in their life form composition, with a higher dominance of large shrubs in upland compared to lowland habitats. Th e outcome of the study revealed a habitat-specific response of vegetation to land use change. But even within the habitats, the vegetation showed plot-specifi c responses of the vegetation to the variances in abiotic factors. We suggest that further analyses should have a stronger focus on species-specific responses at the different sites and employ a more refined life form classification, adapted for the Succulent Karoo vegetation. |
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| Citation |
Schmiedel, U. & Oldeland, J. (2018) Vegetation dynamics in the Namaqualand Hardeveld - observations from 17 years of annual monitoring In: Climate change and adaptive land management in southern Africa – assessments, changes, challenges, and solutions (ed. by Revermann, R., Krewenka, K.M., Schmiedel, U., Olwoch, J.M., Helmschrot, J. & Jürgens, N.), pp. 450-457, Biodiversity & Ecology, 6, Klaus Hess Publishers, Göttingen & Windhoek. doi:10.7809/b-e.00358 |
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