Figure 9. Average primary productivity of grazing areas in Argentina derived from NOAA/AVHRR remotely sensed data for 1981-1999. Rain forest and croplands are excluded from the analysis. Green intensity show increasing primary productivity. Graphs on the right side show the Normalized Difference Vegetation Index (NDVI) seasonality for six selected areas with contrasting patterns. The NDVI is a surrogate of the primary productivity (ANPP) and then of stocking rate (Oesterheld et al. 1998).