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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
environmental science
Twenty years of rest returns grazing potential, but not palatable plant diversity, to Karoo rangeland, South Africa
Journal of Applied Ecology, Volume 47, No. 4, Year 2010
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Description
Up to 73% of the world's rangelands are degraded, and increasing demand for meat in developing countries and a growing human population are likely to exert even greater pressures on rangelands in the next 20-50 years. Restoration of rangeland grazing potential and resilience is therefore important, particularly in the face of climate change.2. We investigated the influence of past stocking rates (from 1910 to 1987), rainfall, and current grazing regimes (from 1988 to 2008) on plant assemblages, grazing potential, and diversity of palatable species in southern Karoo rangelands, South Africa.3. We used herbivore exclusion experiments to test whether resting rangeland for 20 years enables recovery of plant assemblages (where seed sources are present within 50 m), regardless of previous grazing history. Mean annual rainfall over this period was 15% higher than the mean annual rainfall for the preceding 80 years and included two exceptionally wet years.4. While rainfall was a primary driver of total vegetation cover, grazing history explained differences in plant species composition: plots with shared historical grazing intensity were more similar than plots with the same grazing regimes between 1988 and 2008.5. In historically heavily-grazed exclusion plots, cover of the palatable species Tripteris sinuata (formerly Osteospermum sinuatum) returned to levels comparable to that in both exclusion and lightly-grazed plots with a moderate grazing history. Five palatable species (Pteronia empetrifolia, Tetragonia spicata, Berkheya spinosa, Hereroa latipetala and Ruschia spinosa) failed to re-establish, however, despite the presence of seed-producing plants nearby. Furthermore, only cover of P. empetrifolia increased significantly in historically moderately-grazed plots. Cover of unpalatable plants (e.g. Pteronia pallens) increased in all plots over time.6.Synthesis and applications. These findings suggest that present species composition of arid shrublands reflects historical management at time scales greater than 20 years. Despite high rainfall enabling the return of grazing potential through recovery of a single forage species, rest alone did not ensure the return of all palatable species, with implications for rangeland resilience. Restoring the full suite of palatable species over management timeframes will require more complex interventions such as reseeding or selective clearing. © 2010 The Authors. Journal compilation © 2010 British Ecological Society.
Authors & Co-Authors
Seymour, Colleen Lynda
South Africa, Pretoria
South African National Biodiversity Institute
Milton, Suzanne J.
South Africa, Cape Town
University of Cape Town
Joseph, Grant Stuart
South Africa, Cape Town
University of Cape Town
Dean, W. Richard J.
South Africa, Cape Town
University of Cape Town
Ditlhobolo, Tsholofelo
South Africa, Cape Town
University of Cape Town
Cumming, Graeme S.
South Africa, Cape Town
University of Cape Town
Statistics
Citations: 80
Authors: 6
Affiliations: 2
Identifiers
Doi:
10.1111/j.1365-2664.2010.01833.x
ISSN:
00218901
e-ISSN:
13652664
Research Areas
Environmental
Study Design
Cross Sectional Study
Study Locations
South Africa