[Comprehensive Evaluation of Ecosystem Services in Garzê Prefecture Based on the Dynamic Coupling Relationship of...

The Garzê Tibetan Autonomous Prefecture, situated in the upper reaches of the Yangtze and Yellow Rivers, serves as an alpine ecologically fragile area and an important ecological barrier. Therefore, the comprehensive assessment of ecosystem services in Garzê Tibetan Autonomous Prefecture is important for maintaining sustainable development. Based on the dynamic coupling relationship of water-soil-carbon, this study utilizes the water balance method-RULSE-InVEST ecosystem services portfolio model to calculate the ecosystem services in Garzê Tibetan Autonomous Prefecture from 2000 to 2020. Additionally, a spatial autocorrelation model is then employed to explore the spatial heterogeneity of ecosystem services. Consequently, a comprehensive assessment model for quantitatively evaluating the ecological environment quality in this region is constructed. The findings revealed that： ① On the time scale, soil conservation decreased by 25.5 million t from 2000 to 2020, which was related to increased soil erosion caused by climate change and human activities. However, water conservation and carbon storage increased by 22.422 billion m³ and 41 million t from 2000 to 2020, respectively, which was related to the implementation of the measures to return grazing land to grassland. ② From the spatial scale, the mean value of ecosystem service at administrative units exhibited a distribution pattern characterized by lower values in the northwest and higher values in the southeast. The southeastern region predominantly consisted of grassland and woodland vegetation coverage. Notably, Garzê, Luding, and Jiulong Counties recorded the highest values at 512.44 mm, 3 438.25 t·hm^-2, and 34 658.28 t·km^-2, respectively. ③ In 2020, water conservation-soil conservation and water conservation-carbon storage in Garzê Tibetan Autonomous Prefecture showed negative spatial correlation on the dual scale of administrative unit and grid, and the low aggregation was distributed in the southeast of the study area. On the other hand, the spatial positive correlation between carbon storage and soil conservation showed a synergistic relationship, with high concentrations distributed in the northwest of the study area. ④ From the administrative unit perspective, the average score of ecosystem services comprehensive assessment based on accumulative and multiplicative showed a trend of first increase, then decrease, and then increase, with the highest values in Jiulong County ranging from 2.51 to 3.00 and 0.71 to 0.80, respectively. Similarly, from the grid scale perspective, the scores of ecosystem services comprehensive assessment also showed a trend of first increase, then decrease, and then increase, and the highest values were distributed in the southeast, with the values ranging from 2.01 to 3.00 and 0.41 to 0.80, respectively. In summary, the results of this study and the assessment framework provide a theoretical basis for ecological environment protection and restoration in Garzê Tibetan Autonomous Prefecture and also provide a reference for the sustainable development of ecosystems in similar alpine ecologically fragile areas.