Ecological restoration zoning in farming-grazing transitional zone based on the supply and demand of the ecosystem services: a case study of the upper reaches of the Sanggan River

The research on ecological restoration zoning, based on the ecological background and socio-economic characteristics of the farming-grazing transitional zone, will contribute to its ecological security and sustainable socio-economic development. The upper reaches of the Sanggan River, located in the farming-grazing transitional zone, were selected as the research area to identify the ecosystem services, including carbon sequestration, food supply, water production and soil conservation. The multi-source data about land use, meteorological observation and statistical yearbooks, etc., were employed in InVEST model and ArcGIS spatial analysis module, to explore the spatial distribution of the supply and demand of the ecosystem services in the upper reaches of the Sanggan River in 2020. Moreover, Quadrant matching method and coupling and coordination model were adopted to conduct research of the zoning of ecological restoration. The results showed that: In 2020, the spatial distribution of the supply of the four ecosystem services in this area was almost consistent with its topography, forming a semi-closed loop of high value around the backbone artery of the Sanggan River. The high demand for ecosystem services was located where densely populated areas occurred. Matching types of the supply and demand of ecosystem services in the river basin were "high supply -high demand" and "high supply-low demand". The average value of coupling and coordination degree between the supply and demand was 0.23, which was in a state of mild imbalance and indicated a mismatch between the supply and demand of ecosystem services. Based on the matching types and coupling and coordination degree of the supply-demand of the ecosystem services as well as the socio-economic characteristics in the upper reaches of the Sanggan River, the tributary was divided into Shentou Springs ecological restoration area, the ecological barrier zone along the northern ancient Great Wall, the sand-fixation belt in Datong Basin, the water conservation and biodiversity protection area along the inner regions of the Great Wall, and the ecological restoration and biodiversity protection area of the Sanggan River. Coupled with the ecological restoration measures such as assisted regeneration, natural restoration, ecological reconstruction, and protection and conservation, the ecological functions of each zone, mainly focusing on carbon sequestration and conservation, cultivated land protection, water conservation, and water and soil conservation, would be greatly promoted.