Changes in phenological sequences of alpine communities across a natural elevation gradient

Change in individual species phenology is often unsuitable for predicting change in community phenology because of different responses of different species to temperature change. However, few studies have observed community phenological sequences in the field. Here we explore the changes in timing and duration of the community phenological sequence (i.e. onset of leaf-out (OLO), first flower bud (FB), first flowering (FF), first fruiting-set (FFS), post-fruiting vegetation (OPFV), first leaf-coloring (FLC) and complete leaf-coloring (CLC)) along an elevation gradient from 3200 to 3800 m in an alpine meadow on the Tibetan plateau. Our results indicate that OLO and FFS significantly advanced and other timings of phenological events significantly delayed at 3200 m compared with higher elevations (3600 and 3800 m). The flowering duration of the community was shortest and other phenological durations (except budding stage and post-fruiting vegetation stage) were longest at 3200 m. The duration of the growing season decreased as elevation increased, and the ratio of the durations of the reproductive period and growing season was smallest at 3200 m. There were negative correlations between the proportion of early-spring flowering functional group plants and FB, and the durations of leafing and post-fruiting vegetation of the community. Positive correlations were found between the proportion of mid-summer flowering functional group plants in the community and these variables. There were significant negative correlations between flowering duration of the community and annual mean air temperature and soil moisture. Therefore, our results suggest that different community compositions might respond differently to climate change.