Estimation And Uncertainty Of Aboveground/Belowground Biomass Of Desert Grassland In Xinjiang Based On RS

Grassland is the most widely distributed system of natural ecosystem.Grassland biomass is an important parameter to measure grassland productivity and carbon sequestration capacity.Therefore,it is necessary to accurately estimate grassland biomass and carry out analysis and researc h on the change pattern and influencing factors of desert grassland in Xinjiang.It is of great significance to the sustainable utilization and carbon storage capacity of natural grasslands in Xinjiang.Based on a variety of remote sensing product data and grassland biomass data,by constructing the optimal inversion model of desert grassland biomass,this study analyzes the uncertainty of temporal and spatial distribution and estimation of desert grassland biomass in Xinjiang,supplemented by trend analysi s,correlation analysis and precision evaluation,and reveals the relationship between the evolution trend of desert grassland biomass and temperature and precipitation.The main conclusions are as follows:（1）Based on a variety of remote sensing product data and measured biomass data,the correlation coefficient and accuracy of the index inversion model are the highest,which is suitable for the monitoring and research of aboveground biomass change of desert grassland in Xinjiang.The precision of the power function model of the belowground biomass of desert grassland is higher than that of the measured root shoot ratio,the uncertainty of desert grassland biomass estimation comes from the estimation accuracy of different remote sensing data sources,root shoot ratio data and allometric growth model.（2）The distribution of desert grassland is concentrated in Northern Xinjiang and scattered in southern Xinjiang.From 2000 to 2019,the NDVI of desert grassland in Xinjiang generally sh owed a trend of gradually increasing from south to north.The NDVI of desert grassland appeared the maximum value（0.15）in 2019 and the minimum value（0.12）in 2010.Among them,the average NDVI of desert grassland was 0-0.2,accounting for 85.43%.Based on the change trend of NDVI,it is found that the desert grassland in Xinjiang is mainly stable and improved,and the area reaches 97.22%.（3）From 2000 to 2019,the temperature and precipitation in Xinjiang showed an upward trend,and the climate showed obvious warm and humid characteristics.The average temperature rise rate and precipitation rate in Xinjiang reached 0.32℃·（10 a）^-1 and 2.18 mm·（10 a）^-1.The correlation between desert grassland biomass,root shoot ratio and precipitation were better than that of temperature.（4）There are obvious spatial differences in the biomass of desert grassland in Xinjiang from 2000to 2019.The spatial pattern of desert grassland biomass is high in the northwest and low in the southeast.The belowground biomass of desert grassland is much greater than the aboveground biomass of desert grassland.The average aboveground,belowground and total biomass of desert grassland in Xinjiang were 52.35 g·m^-2 1614.27 g·m^-2and 1666.25 g·m^-2 respectively.The proportion of areas with above ground,belowground and total biomass change rate greater than zero in desert grassland was 98.70%,87.17%and 58.56%respectively.The average carbon density of aboveground,belowground and total biomass of desert grassland was 23.53 g C·m^-2,725.64 g C·m^-2 and 749.18 g C·m^-2 respectively.The total aboveground,belowground and total biomass carbon of desert grassland were 5.84 Tg C,179.81Tg C and 185.65 Tg C respectively.