Skip all navigation and jump to content Jump to site navigation
NASA Logo - Goddard Space Flight Center

+ NASA Homepage

    
Goddard Space Flight Center
About MODIS News Data Tools /images2 Science Team Science Team Science Team

   + Home
ABOUT MODIS
MODIS Publications Link
MODIS Presentations Link
MODIS Biographies Link
MODIS Science Team Meetings Link
 

 

 

Wessels, KJ, Prince, SD, Carroll, M, Malherbe, J (2007). Relevance of rangeland degradation in semiarid northeastern South Africa to the nonequilibrium theory. ECOLOGICAL APPLICATIONS, 17(3), 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 (Sigma NDVI), calculated using data from both the Advanced Very High Resolution Radiometer (AVHRR) (1985-2003) and Moderate-resolution Imaging Spectrora-diometer (MODIS) (2000-2005). On average, rainfall and degradation accounted for 38% and 20% of the AVHRR Sigma NDVI variance and 50% and 33% of the MODIS Sigma NDVI 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.

DOI:

ISSN:
1051-0761

FirstGov logo Privacy Policy and Important Notices NASA logo

Curator: Brandon Maccherone
NASA Official: Shannell Frazier

NASA Home Page Goddard Space Flight Center Home Page