Climate warming alters the start (SOS) and end (EOS) of growing seasons, impacting biotic interactions and biogeochemical cycles, yet the carry-over links between SOS and EOS remain poorly understood, limiting future projections. Using MODIS satellite-derived phenology data for seasonal vegetation and European ground observations for deciduous tree species, we show that an earlier SOS typically advances the EOS on average by 0.19 ± 0.001 days per day (MODIS) and 0.10 ± 0.002 days per day (ground), while EOS exerts a weaker influence on subsequent SOS. The SOS-to-EOS effect often outweighed abiotic factors, with SOS emerging as the best predictor of EOS in 34% of pixels (β = 0.27). When predicting SOS, EOS was the primary predictor in only 7.9% of pixels, while preseason temperature dominated in 58% (β = -0.33). More importantly, we identified a dampening interaction, where an increase in one carry-over effect reduced the other. Thus, the SOS-to-EOS effect was twice as strong as the EOS-to-SOS effect in temperate deciduous forests, while the EOS-to-SOS effect was up to three times stronger in boreal taiga and tundra. The observed carry-over effects likely reflect developmental (cell and tissue growth) and stress-related constraints (SOS-to-EOS effect), as well as chilling requirements (EOS-to-SOS effect at high latitudes). These findings highlight how physiological feedback affects phenological responses to climate change, emphasizing the need to integrate plant-internal carry-over effects into future ecosystem models.
Wu et al. (Sun,) studied this question.