Soil erosion is an important global environmental problem that signicantly impacts regional environmental quality and the social economy. Ecosystems protect soil from water and wind erosion and thereby provide "soil erosion control services," which is one of the most fundamental ecosystem services that safeguard human welfare. Chongqing Region is one of the most important ecological zones in China, and is located on the upper reaches of the Three Gorges Reservoir Area (TGRA), which is the largest dam project worldwide. The status of the ecosystem functions in Chongqing Region directly affects the TGRA. Recently, the ecological environment of this region has rapidly changed because of extensive change in land cover, due to rapid population growth and economic development. In addition to climate change mitigation and adaption, global changes in climate have highlighted the role of ecosystems in soil conservation. Owing to a combination of natural factors and recent human activities, soil erosion in certain parts of the Chongqing Region is becoming increasingly serious. However, few studies have focused on the quantitative estimates of the soil conservation service and its ecological value in the Chongqing Region.
This study aimed to construct the C value layer of different land cover types and different vegetation coverage based on the table lookup method. In addition, soil loss and soil conservation services in Chongqing Region were evaluated by geographic information system (GIS) technology and the universal soil loss equation (USLE) with localized parameters. The spatial patterns of the soil conservation service and its ecological value were revealed. The results of the study indicate that, compared to the single land cover assignment method, the improved C value layer containing more spatial information enhances the accuracy of soil erosion results. To verify that this model may be reliability applied, we validated the model results based on observed data and statistical data based on average annual estimates between 2006 and 2010. Simulations of average annual soil erosion rates agreed well with the observation-based data (R²=0.85, P=0.000), which indicated that the simulated models may be used to infer soil erosion levels in this study. The results of the models showed that the total amount of soil loss and soil conservation services in Chongqing Region are 2.23×10⁸ t/a and 14.69×10⁸ t/a, respectively. Furthermore, we found that the soil conservation service improved from 2006 to 2010 as a result of vegetation restoration. Moreover, market valuation, opportunity cost, and shadow engineering methods were used to evaluate the ecological value of the soil conservation service. The total value of the soil conservation service in 2010 was about 6.18×10⁹ yuan (RMB) /a, of which, about 5.44×10⁹ yuan was of holding nutrients for N, P and K, about 2.65×10⁸ yuan was of decreasing soil loss, and about 4.78×10⁸ yuan was reducing reservoir silt. In addition, ecosystems located in the counties of Wuxi, Chengkou, and Fengjie (i.e., the east mountain areas), had much better erosion control than ecosystems in the west, and generally displayed much higher ecological value than the west with a capacity of >2×10⁸ yuan/a. Among all ecosystem types, forests were superior in the total amount and capacity of soil conservation service value. These results provide specific information that is necessary for strengthening public awareness about protecting and restoring ecosystems.