Climate warming shifts the time interval between flowering and leaf unfolding depending on the warming period

The timing of flowering (FL) and leaf unfolding (LU) determine plants' reproduction and vegetative growth. Global warming has substantially advanced FL and LU of temperate and boreal plants, but their responses to warming differ, which may influence the time interval between FL and LU ( increment LU-FL), thereby impacting plant fitness and intraspecific physiological processes. Based on twigs collected from two flowering-first tree species, Populus tomentosa and Amygdalus triloba, we conducted a manipulative experiment to investigate the effects of winter chilling, spring warming and photoperiod on the increment LU-FL. We found that photoperiod did not affect the increment LU-FL of Amygdalus triloba, but shortened increment LU-FL by 5.1 d of Populus tomentosa. Interestingly, spring warming and winter chilling oppositely affected the increment LU-FL of both species. Specifically, low chilling accumulation extended the increment LU-FL by 3.8 and 9.4 d for Populus tomentosa and Amygdalus triloba, but spring warming shortened the increment LU-FL by 4.1 and 0.2 d degrees C-1. Our results indicate that climate warming will decrease or increase the increment LU-FL depending on the warming periods, i.e., spring or winter. The shifted time interval between flowering and leaf unfolding may have ecological effects including affecting pollen transfer efficiency and alter the structure and functioning of terrestrial ecosystem.

Automated summary

The study found that photoperiod did not affect the increment LU-FL of Amygdalus triloba, but shortened the increment LU-FL of Populus tomentosa. Spring warming and winter chilling had opposite effects on the increment LU-FL of both species, indicating that climate warming may decrease or increase the increment LU-FL depending on the warming periods.