Exploring suitable topographical factor conditions for vegetation growth in Wanhuigou catchment on the Loess Plateau, China: A new perspective for ecological protection and restoration

Ecological degradation has become an important constraint to global socio-economic development. Therefore, ecological protection and restoration has received increasing attention. The important goal and the most direct effect of ecological protection and restoration are the vegetation restoration, which emphasizes the maximum or minimum range of NDVI of different vegetation types under specific terrain conditions. Based on the data of NDVI and topographic factors in a stable ecosystem, this paper comprehensively used descriptive statistics, multiple regression with interaction terms and threshold regression to analyze the spatial distribution of vegetation and its relationship with elevation, slope and aspect in the Wanhuigou catchment on the Loess Plateau. It showed that the NDVI values were high in the northwest and low in the southeast, and were generally consistent with the distribution of elevation. The change of NDVI with the slope was large, but the change with the aspect was not obvious. Meanwhile, the effect of elevation on NDVI would be limited by slope, but would not be affected by aspect; the positive effect of slope on NDVI would also be limited by the elevation and aspect. In addition, the influence of topographic factors on NDVI was non-linear, i.e. there was a threshold effect and different types of vegetation require different topographic factor conditions. Therefore, by rationally arranging the growth areas of different types of vegetation in accordance with the laws of topographic factor conditions, ecological protection and restoration could be more targeted to help build a stable ecosystem in areas with severe soil erosion such as the Wanhuigou catchment.