Monitoring of grassland herbage accumulation by using remote sensing in Gannan Prefecture

This study focuses on grasslands in the Gannan Prefecture, we used the measured data of aboveground grassland biomass (AGB) and the MOD13Q1 vegetation index product from 2016 to 2019, to construct a remote sensing inversion model of grassland AGB, and further analyzed the characteristics of temporal and spatial changes in the grassland AGB in the last 20 years (from 2000 to 2019). The results showed that: 1) Our moderate resolution imaging spectroradiometer enhanced vegetation index (MODIS EVI) is suitable for grassland biomass inversion (R² = 0.524 9, RMSE = 527.9 kg·ha⁻¹). 2) In the past 20 years, the alpine meadows and mountain meadows showed an increasing trend, while swamp AGB decreased. 3) In the past 20 years, the grasslands in Gannan Prefecture showed a trend towards partial deterioration; the overall trend for grassland vegetation in Gannan Prefecture was positive, 66.04% of the grassland showed a trend of stabilization or recovery, 33.96% of the grassland AGB decreased, and 18.08% of the grasslands showed a continuous deterioration trend. The study results provide data support for Gannan Prefecture grassland vegetation dynamic monitoring and alpine grassland degradation restoration.