Linking Climate Sensitivity of Plant Phenology to Population Fitness in Alpine Meadow

Timings of phenological events have been paid more attention in facing of climate change. However, little is known how shifts of phenological events are associated with variations of vegetative and reproductive periods which could further link to population fitness over time. We compiled an observational data set including timings of four phenological events, height, and population aboveground biomass of 12 plant species across five sites in alpine meadow on Tibetan Plateau spanning 1988-2006. Our time-series data revealed timings of budburst and flower budding are more sensitive to climate warming than timings of fruit ripeness and leaf senescence. Some species showed advances of budburst and/or flower budding, and others did not show any response. We also found advance of budburst was correlated with lengthening of vegetative and activity period, and advance of flower budding was correlated with shortening of vegetative and lengthening of reproductive period. Furthermore, negative relationship was found between budburst shifts and aboveground biomass suggesting advance of budburst is beneficial to population fitness over time under warming. Our spatial-data showed lengthening vegetative period due to budburst advance was correlated with increase of aboveground biomass as comparison the species pairs in a warm-wet site with that in a cold-dry site. Prolonging reproductive period due to flower budding advance was correlated with increase of aboveground biomass as comparison the species pairs in a warm-dry site with that in a cold-wet site. Our study suggests linking phenology to population fitness is helpful to better understanding diverse responses of phenological events to climate changes.