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Please use this identifier to cite or link to this item: http://hdl.handle.net/10204/1609

Title: Relevance of rangeland degradation in semiarid Northeastern South Africa to the nonequilibrium theory
Authors: Wessels, KJ
Prince, SD
Carroll, M
Malherbe, J
Keywords: AVHRR
Communal land
Grazing
Land degradation
MODIS
NDVI
Nonequilibrium
Rainfall
Rangeland
South Africa
Issue Date: Apr-2007
Publisher: Ecological Society of America
Citation: Wessels, KJ et al. 2007. Relevance of rangeland degradation in semiarid Northeastern South Africa to the nonequilibrium theory. Ecological Applications, Vol. 17(3), pp 815-827
Abstract: According to the nonequilibrium theory, livestock grazing has a limited effect on long-term vegetation productivity of semiarid rangelands, which is largely determined by rainfall. The communal lands in northeastern South Africa contain extensive degraded areas which have been mapped by the National Land Cover (NLC) program. Much evidence suggests that long-term heavy grazing is the cause of this degradation. In order to test for the prevalence of nonequilibrium dynamics, we determined the relative effects of rainfall- and grazing-induced degradation on vegetation productivity. The vegetation production in the NLC degraded areas was estimated using growth-season sums of the Normalized Difference Vegetation Index (RNDVI), calculated using data from both the Advanced Very High Resolution Radiometer (AVHRR) (1985–2003) and Moderate-resolution Imaging Spectroradiometer (MODIS) (2000–2005). On average, rainfall and degradation accounted for 38% and 20% of the AVHRR RNDVI variance and 50% and 33% of the MODIS RNDVI variance, respectively. Thus, degradation had a significant influence on long-term vegetation productivity, and therefore the rangelands did not behave according to the nonequilibrium model, in which grazing is predicted to have a negligible long-term impact.
Description: Copyright: 2007 Ecological Society of America
URI: http://hdl.handle.net/10204/1609
ISSN: 1051-0761
Appears in Collections:Remote Sensing
General science, engineering & technology

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