Natural Ecological Background of Terrestrial Vegetation in China: Identification Methods and Spatial Differentiation Characteristics

The closeness of the value of regional ecological parameters to the value of the natural ecological background can be used to efficiently evaluate the effectiveness of vegetation protection and ecological restoration. Advances in remote sensing technology have promoted the use of terrestrial ecosystem parameters obtained by multispectral sensors to identify the ecological background. Therefore, it is important to identify and construct the natural ecological background. By considering the authenticity of nature reserve ecosystems and the spatial differentiation of vegetation ecosystems, in this study we established an identification method for the natural ecological background of vegetation predicated upon a complete geographical unit. In China, land is divided into 106 regions based on different ecosystem functions. Additionally, 292 national nature reserves have been established throughout the country to conserve unique forest and grassland ecosystems. Using the spatial relationship between ecological function regions and the national nature reserves, ecological units of the natural ecological background were identified. The natural ecological background included two types of ecosystems: forest and grassland. It was composed of the current background, recovery rate background, and stability background, including four vegetation parameters that can effectively reflect the vegetation function and community structure: gross primary productivity (GPP), net primary productivity (NPP), leaf area index (LAI), and fractional vegetation cover (FVC). The spatial characteristics of the natural ecological background based on this method were clearly observed. These spatial characteristics are consistent with the ecosystem types and their combination characteristics, the soil and water conditions required for vegetation growth, and the corresponding ecosystem services. Therefore, the findings hold certain objectivity, have a scientific basis, and can be used as a reference for evaluating the effectiveness of terrestrial ecosystem protection and restoration in China.