Analysis of grassland phenology dynamics and response to seasonal scale climate, topography in China based on geodetector for the period 2001 to 2019

Introduction There is limited research on the cumulative effects of seasonal climate factors and the combined impacts of climate and topography on grassland phenology. This gap hinders the understanding of the climate adaptability of China’s grasslands ecosystems. Methods This work used the GeoDetector method to examine how grassland phenology in China (CGP) responds to seasonal climate factors, elevation, slope, and aspect. First, we studied the spatiotemporal distribution characteristics of CGP through spatial analysis and trend analysis methods. Second, we examined the effects of different climatic factors on CGP at the seasonal scale through correlation analysis. Third, we classified the topography of the study area and investigated the influence of different terrains on CGP. Finally, GeoDetector was used to quantify the explanatory power of seasonal climate and topography on CGP, as well as the impact of climate-topography interactions on CGP. Results and Discussion The results showed that with increasing preseason length, the areas showing a negative correlation between temperature and the start of season (SOS) expanded. SOS was negatively correlated with precipitation and evapotranspiration, except precipitation of the previous year and evapotranspiration in winter. Temperature, precipitation, and evapotranspiration all showed positive correlations with the end of season (EOS). The responses of SOS to elevation and slope exhibited nonlinear trends. When elevation exceeded 4 km, the rate of SOS delay accelerated markedly. SOS also showed significant delays at slopes greater than 25°. Meanwhile, with increasing elevation and slope, EOS tended to advance. The interaction effects of climate and topography on EOS were weaker than those on SOS. SOS (EOS) is primarily influenced by the interaction between elevation and evapotranspiration (precipitation), highlighting the importance of the interaction between DEM and climatic factors in shaping grassland phenology in China. The findings in this work suggest that topographic heterogeneity should be incorporated into ecological management to better respond to environmental challenges under climate change.