Title:

Vegetation dynamics in the Namaqualand Hardeveld - observations from 17 years of annual monitoring

Publication Year:
2018
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. The recording commenced one year after 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 shifted away from the initial state. The year-to-year species turnover per habitat, however, was greater on lowland compared to upland habitats. The 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. The outcome of the study revealed a habitat-specific response of vegetation to land use change. But even within the habitats, the vegetation showed plot-specific 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.

Publication Title:

Climate change and adaptive land management in southern Africa - assessments, changes, challenges, and solutions

Place:
Göttingen and Windhoek
Editor:
Revermann R, Krewenka KM, Schmiedel U, Olwoch JM, Helmschrot J, Jürgens N
Publisher:
Klaus Hess Publishers
Series Title:
Biodiversity and Ecology
Series Number:
6
Pages:
450-457
Item Type:
Book or Magazine Section
Language:
en