Monthly Multi-Source Remote Sensing Reveals Seasonal Pulses, Bundle Transitions, and Differentiated Management of Ecosystem Services in the Yongding River Basin

Seasonal basin management requires knowing when ecosystem services coincide and how their configurations differ among subbasins, information that annual summaries can obscure. We integrated monthly remote sensing, meteorological, soil, and terrain data to estimate carbon fixation (CF), water conservation (WC), soil retention (SR), and wind erosion prevention (WEP) in 18 Yongding River subbasins in 2018, 2020, and 2023. Seasonal association networks and a self-organizing map characterized 648 subbasin–month service profiles and their bundle histories. Of 648 monthly bundle labels, 237 (36.6%) differed from the label of the corresponding annual mean service vector. The high-CF–WC–SR bundle occurred in 26 monthly profiles, including 19 of 54 July observations, whereas subbasin 4 retained a WEP-oriented bundle in 30 of 36 sampled months. In the three-year mean seasonal profiles, 12 of 18 subbasins shared a summer CF-enhanced pathway; the other six followed alternative pathways. CF, WC, and SR were generally higher in summer, while WEP peaked in April and was more prominent in western and southwestern subbasins. Seasonal networks showed the strongest screened association for winter SR–WC, while the summer WC–WEP confidence interval crossed zero. Together, monthly bundle histories and seasonal association networks identify shared summer assessment windows and subbasin-specific priorities for spring wind exposure and service-bundle transition monitoring, providing spatially and temporally explicit evidence for differentiated seasonal management in the Yongding River Basin.