Lengthened flowering season under climate warming: Evidence from manipulative experiments

Abstract Climate warming potentially changes the flowering seasons of terrestrial plants, and thus species interaction, with consequently substantial impacts on ecosystem structure and function. However, the general response patterns of flowering seasons to warming and the underlying mechanisms remain poorly understood. Here, a meta-analysis of data from 26 experimental studies examining 168 species was conducted to quantify the responses of the flowering seasons of terrestrial plants to experimental warming. The results showed that experimental warming prolonged the flowering season by 2.08% across all species included in this study. In addition, flowering season responses were dependent on plant functional types, with a significant extension in herbaceous species (+2.18%) but no change in woody species. The warming impacts on the flowering season of wind-pollinated (-4.53%) and insect-pollinated species (+4.21%) were opposite. Among herbaceous species, the flowering seasons of forb (+4.47%) and specifically legume species (+15.06%) were positive, whereas grass species (-4.53%) showed negative responses to experimental warming. Moreover, experimental warming effects on the flowering season showed quadratic relationships with the latitude and the mean annual temperature but did not change with the mean annual precipitation. The responses of the flowering season to experimental warming also differed in terms of the warming magnitude. These diverse findings indicate the need for additional experimental warming experiments, especially for underrepresented plant functional groups, to better understand the mechanistic relationships between phenology and temperature under future climate warming scenarios.