Estimating Pasture Productivity in the Brazilian Savanna Biome Based on Moderate Resolution Satellite Data

Brazil has the largest commercial beef cattle herd in the world (over 190 million head in 2006) [1], with cultivated pastures occupying about 150 million hectares of its territory [2]. On a biome basis, the most extensive pasture occupation is found in the Cerrado (~ 546,251 km, amounting to about 26.8% of the total biome area and 36.8% of the total pasture area in Brazil), the Brazilian savanna biome, located mostly in central Brazil and comprising a complex mosaic of physiognomic categories, ranging from grassland to forest formations (figure 1). In relation to the Cerrado ́s cultivated pastures, it is estimated that at least 50% are already severely degraded [3], as indicated by the dominance of invading species, common occurrence of termite hills, loss of soil fertility, and decrease in biomass, leading to substantial losses in soil carbon [4, 5]. On the contrary, increases in soil carbon, up to 17%, are observed as pasture productivity recovers [6]. Primary productivity can be considered as a proxy for identifying and mapping degraded areas [7] and it can be estimated from orbital data [8, 9]. In terms of Cerrado ́s cultivated pastures, primary productivity varies mainly according to species and management practices, yielding distinct spectral responses along a full hydrological cycle. In this context, we present some preliminary results regarding our attempt to map, at the biome scale, the Cerrado ́s pasture conditions based on the time-domain analysis of the MODIS vegetation indices.