Grazing effect on NDVI across an aridity gradient in Argentina.

BLANCO, L.; AGUILERA M.O.; PARUELO J.M.; BIURRUN, F.N.

JOURNAL OF ARID ENVIRONMENTS

Año: 2008 vol. 72 p. 764 - 776

0140-1963

Grazing effects on aboveground net primary production (ANPP) have ever been controversial. Certain plantcommunities are very sensitive to grazing and others are not. We analyzed the grazing effect on ANPP across a gradient ofmean annual precipitation (MAP) in rangelands of Central Argentina. We focused not only on the regional patterns ofthe grazing effect on ANPP but also on the response of the inter-annual variability of ANPP to this disturbance. We usedthe seasonal dynamics of the Normalized Difference Vegetation Index (NDVI), a spectral index calculated from thereflectance in the red and infrared portion of the spectrum as recorded by the AVHRR/NOAA sensor as an estimator ofANPP. This variable was recorded at increasing distances from the watering point in large paddock distributed throughthe MAP gradient (250–600mm) of the extensive plains Arid Chaco in Argentina. Grazing effect on NDVI decreasedalong the regional gradient of MAP. The grazing effect on NDVI varied among years, being greater in dry than in wetyears. Regional patterns changed among years because the NDVI close to the watering points had high inter-annualvariability at the driest extreme of the gradient. Our findings contribute a conceptual framework to grazing management insemi-arid rangeland. Considering that grazing effect on NDVI-I was higher in arid than in wet sites implicates thatappropriate grazing management strategies would be different in sites with different precipitation levels.r 2007 Elsevier Ltd. All rights reserved.