Carbon flux simulation of major natural vegetation and projected changes under SSP scenarios in the Yarlung Tsangpo–Lhasa–Nyangchu region.

The modeled vegetation area within the research area is 51563.28 km ², accounting for 77.3% of the total area; The average annual GPP and NPP during the historical period were 14.184 and 7.661 TgC, respectively, with an overall CUE of 0.540. The GPP per unit area of shrubs is higher than that of grasslands, and grasslands play an important role in regional productivity due to their area advantage; The area of coniferous forests is extremely small and does not constitute the main source of regional total.

The spatial differences between GPP and NPP models are positively correlated with regional products, but their interannual variations are inconsistent, and the downward trend of the model cannot be used as a definitive conclusion on regional changes. Both grassland and shrub GPP are strongly positively correlated with precipitation, and the partial correlation coefficients after controlling for temperature and radiation are 0.67.

Within the same scenario driven system, GPP from 2071 to 2100 increased by 8.6%, 17.4%, 20.5%, and 28.3% respectively compared to 2015-2024, with corresponding NPP increases of 10.1% -28.8%. The long-term CUE is 0.544-0.549; These increases have not yet ruled out the impact of simulating the initial transition. The above results indicate that under the current model and parameter settings, there is a possibility of an increase in the productivity of the main natural vegetation with changes in the scenario.

However, the correlation between its magnitude and climate needs to be understood in conjunction with model bias, and the actual net carbon sink enhancement cannot be directly inferred from the increase in productivity.