RANGE ASSESSMENT USING REMOTE-SENSING IN NORTHWEST PATAGONIA (ARGENTINA)

A methodology based on remotely sensed data (LANDSAT-MSS) was used for rapid assessment of rangelands in the grass and shrub steppes of NW Patagonia (Argentina). We calibrated Normalized Difference Vegetation Index (NDVI) data using total plant cover, grass cover, shrub cover, and floristic data. Total vegetation cover and grass cover was predicted with high accuracy from Normalized Difference Vegetation Index data. The correlation between observed and estimated cover was 0.87 and 0.82 (p<0.01) for total cover and grass cover respectively. The correlation was lower for shrub cover than for grass (r=0.45, p<0.01). Normalized Difference Vegetation Index data was used to accurately predict cover of Festuca pallescens (St. Yves) Parodi (coiron blanco) and Nassauvia glomerulosa (Lag.) Don (colapiche), 2 species with contrasting response to grazing in the Occidental district of Patagonia, and typical of vegetation with very different grazing values. The correlation between observed and estimated from the Normalized Difference Vegetation Index cover was 0.67 and 0.53 (p<0.01) for Festuca pallescens (coiron blanco) and Nassasuvia glomerulosa (colapiche) respectively.