Modeling aboveground biomass of an alpine desert grassland with SPOT-VGT NDVI

Grassland biomass on the Qinghai-Tibet Plateau is of great significance for the study of wildlife habitat and climate change. Based on Systeme Pour l’Observation de la Terre Vegetation normalized difference vegetation index (NDVI) data from 1998 to 2012 and a field survey investigation in 2013, we assessed aboveground biomass (AGB) dynamics in the Altun Mountain Nature Reserve. The results demonstrated that annual NDVI values varied greatly with an increasing trend. Areas of high- and medium-coverage grassland showed similar increasing trends. The NDVI–biomass relationship could be quantified by an exponential model and previous models overestimated the amount of biomass in the alpine desert grassland. The total biomass was estimated to be 62 × 106 kg per year with large annual variations. No significant relationship was found between AGB and soil organic carbon contents, and the total grassland area (NDVI > 0.1) was positively correlated with the annual average temperature.