Objective To investigate the divergent responses of plant phenology to seasonal temperature in warm temperate forests in Doling Mountain, Beijing.

Method By using data of 6 phenophases of 24 woody plants in warm temperate forests in Beijing during 2003 and 2019, we calculated temperature relevant periods of different phenophases to seasonal temperature by using Partial Least Square regression and correlation analysis and compared the corresponding temperature sensitivities in these periods by Wilcoxon signed-rank test.

Result Temperature relevant periods of leaf unfolding dates, first flowering dates and full flowering dates were 48, 64 and 55 days before the phenological dates (early-mid March to late April or early-mid May), respectively. For every increase of 1 °C, the flowering period was advanced by an average of 6.38 days, which was significantly higher than that of the leaf development period (4.52 days earlier) and full flowering period (5.05 days earlier). The response mode of germination period to temperature was different from the above three phenophases, and its optimal correlation period was from October 28th to January 14th in autumn and winter, followed by March 11th to April 14th in winter and spring (34 days before germination) and summer from July 14 to August 27. For every temperature increase of 1 °C in autumn and winter, the date of budburst advanced by 5.48 days, which was significantly higher than the number of days (3.71 days) that the temperature in winter and spring advanced (3.71 days), while the temperature increase of 1 °C in summer delayed the budburst by 9.74 days, which was significantly different from other. The optimal correlation period of the leaf coloring and defoliation stages to the temperature response was from early April to mid-to-late July in spring and summer, and the species that responded significantly to temperature in summer and autumn (late August to mid-to-late September) rare. When the temperature increased by 1 °C, the temperature in the spring and summer related periods brought forward the leaf coloring and leaf defoliation periods by 7.12 and 9.55 days, respectively, while the summer and autumn temperatures delayed them by 2.27 and 5.96 days, respectively. In the past 50 years, the temperature rise rate in late winter and early spring (February and March) at the research site was more than twice that of other months, while the temperature in autumn and winter (October-December) had no significant change.

Conclusion The divergent responses of plant phenology to seasonal temperature and seasonally asymmetric warming may exert profound impacts on plants and the entire ecosystem.