## 3 Data and Methods
### Index System  
The spatial distribution of ecosystem quality is generally the result of multiple factors [47; 48], including physical elements and human elements. Physical elements are innate factors that affect the quality of the ecological environment. Human society can optimize, interfere with, or disrupt the regional ecological environment through a series of activities. By consulting the relevant research results and following the principles of scientific investigation, comprehensiveness, and independence, this study selected different factors from the three aspects of the physical elements, the socioeconomic elements, and policy adjustments in order to construct an index system of the driving factors of changes in ecosystem quality in Henan Province. See Table 1 for the specific indicator system.  
Physical elements are the basis for the formation of the spatial patterns of ecosystem quality. In this study, four indices covering topography, climate, and land use were selected to reflect the differences in the region's natural conditions. Topographic development is slow, but it is an important factor affecting the spatial patterns of ecosystem quality. Therefore, relief amplitude was selected to measure the effects of topography on the distribution pattern of ecosystem quality. Climate factors are the most direct and sensitive factors that affect the regional changes in the ecological environment. The average annual rainfall and average annual temperature play a decisive role in driving the evolution of ecosystem quality at the spatiotemporal scale. Land use diversity was used to reflect the intensity of interference of human activities in the changes in natural surface elements.  
The impact of social economy on ecosystem quality is the most flexible. This study chose population density and average GDP to reflect the intensity of human activities. At the same time, national or local policy adjustments have an important impact on the evolution of ecosystem quality. Therefore, in order to systematically study the evolutionarymechanism of ecosystem quality in Henan Province, this study selected programs of turning farmland into forests, natural forest protection programs, and shelter forest programs to analyze their impacts on changes in the ecological environment and to measure the effectiveness of policy regulations in the evolution of ecosystem quality. All the data in this study use the individual counties of Henan Province as the statistical unit to build the index database. Through the use of the ArcGIS10.3 software, the quantitative and spatial evolution of ecosystem quality in Henan Province were realized.  
In order to verify whether there was redundant information in the driving factors, this study used SPSS to diagnose any collinearity between the independent variables. The variance inflation factor and tolerance were used to perform multivariate collinearity tests among the indicators. When the collinearity of the index is strong, the variance expansion factor is larger. A value of less than 10 indicates that the collinearity is not obvious, and a score above 10 indicates that the collinearity is obvious. Tolerance is the reciprocal of the variance inflation factor, so it is bounded by 0.1. The smaller the tolerance, the stronger the collinearity. By extracting the driving factor indices and _EQI_ of 123 county units in Henan Province for the collinearity test, the results show that there was no collinearity among all driving factors, and the selected indices are scientific and reasonable (see Table 2).