[Seasonal Response of Ecological Environmental Quality to Climate Change on the Loess Plateau]

The response of ecological environmental quality to climatic factors exhibits distinct seasonal variations, especially in regions with strong fluctuations in temperature and precipitation. Using remote sensing imagery and meteorological data from 2000 to 2022, this study quantitatively assessed the seasonal dynamics of ecological quality and its sensitivity to climatic drivers. The results are as follows: ① The interannual variation of the k-modified remote sensing ecological index (kRSEI) showed clear seasonal differences. kRSEI increased gradually in spring and summer, indicating ecological improvement, but declined in autumn with large interannual fluctuations. ② Spatially, ecological quality exhibited a stepwise degradation pattern from southeast to northwest. As the seasons progressed, regional disparities in ecological quality narrowed, and transitions between ecological grades became smoother. ③ Among climatic variables, the standardized precipitation evapotranspiration index (SPEI) and average temperature (Tavg) were the dominant drivers of kRSEI change. The spatial sensitivity pattern was characterized by stronger responses in the northwest during spring and autumn and in the central and southern regions during summer. In mountainous and arid areas, climatic factors were negatively correlated with ecological quality. ④ Ecological quality differed significantly across land use types, ranked as: forest > cropland > shrubland > grassland > impervious surface > barren land. In particular, kRSEI in shrubland and grassland showed higher sensitivity to SPEI and Tavg in summer and autumn. Natural ecosystems, such as forests, shrublands, and grasslands, exhibited stronger responses to climatic factors compared to land types with higher levels of human disturbance, such as croplands and impervious surfaces. These findings highlight the importance of incorporating seasonal perspectives when evaluating ecosystem responses and improving the precision of climate sensitivity assessments.