Aboveground Biomass Estimates of Grassland in the North Tibet Using Modis Remote Sensing Approaches

Grassland biomass is a key biophysical metrics to characterize grassland growth and a sensitive indicator of environmental change and ecological functioning. The quantification and timely information on aboveground biomass (AGB) of grassland are crucial for the sustainable use and management of grassland resources. In this study, AGB for main grassland types in the North Tibet was analyzed using field measurements and climatic controls of variations of aboveground biomass were explored, and the general estimate models for grassland AGB were further developed based on the relationships between MODIS vegetation indices (VIs) and the field measurements. The results indicated that alpine swamp meadow has the highest AGB of 356.8 g/m 2 on average, followed by temperate steppe (64.5 g/m 2 ) and alpine meadow (61.6 g/m 2 ), and AGB of alpine steppe is lowest at 48.9 g/m 2 . Precipitation is main climate factor impacting variations of grassland AGB. The exponential relationships existed between grassland AGB and MODIS VIs and exponential models based on MODIS NDVI were found to be optimum for monitoring and estimating grassland AGB. Study also showed that AGB in the North Tibet spatially decreases from southeast to northwest, which is above 100 g/m 2 in the southeast and is below 20 g/m 2 in the northwest.