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

Link:
Autor/in:
Erscheinungsjahr:
2018
Medientyp:
Text
Beschreibung:
  • 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 diff ered 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-specifi c 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-specifi c responses at the diff erent sites and employ a more refi ned life form classifi cation, adapted for the Succulent Karoo vegetation.
Lizenz:
  • info:eu-repo/semantics/openAccess
Quellsystem:
Forschungsinformationssystem der UHH

Interne Metadaten
Quelldatensatz
oai:www.edit.fis.uni-hamburg.de:publications/ffca62ff-1967-4ca5-96a6-09e3b2dd4c82