Accurate estimation of ecosystem carbon stocks and their dynamics and exploration of their drivers will contribute to the sustainable management of carbon neutrality. We combined field measurements in China's West Liao River Basin with the improved Terrestrial Ecosystem Regional (TECO-R) model to quantify the carbon pools and carbon turnover time from 2000 to 2021. Ecosystem carbon density averaged 3.65 kg C m-2; soil carbon pools accounted for about 80 %. Forests are major contributors to carbon sinks. The turnover times in the leaf, root, and soil carbon pools and the whole ecosystem were 0.54, 5.26, 42.76, and 23.31 years, respectively, depended on elevation and vegetation type. Although warming and increased precipitation promoted vegetation carbon accumulation, this increase was offset by a more substantial loss of soil organic carbon, the entire ecosystem (ec) decreased at an average rate of 84.21 g C m-2 yr-1, mainly due to enhanced soil carbon loss. Precipitation significantly affects the ecin arid and semi-arid river basin; human activities and the natural environment also directly or indirectly influenced the evolution of ec. Our hybrid modeling framework enables spatially explicit assessment of carbon dynamics and provides a transferable approach for management, and guide nature-based climate solutions in fragile ecosystems.