Flowering phenology in a species-rich temperate grassland is sensitive to warming but not elevated CO2

Abstract

• Flowering is a critical stage in plant life cycles, and changes might alter processes at the species, community and ecosystem levels. Therefore, likely flowering-time responses to global change drivers are needed for predictions of global change impacts on natural and managed ecosystems. • Here, the impact of elevated atmospheric CO2 concentration ([CO 2]) (550 μmol mol-1) and warming (+2°C) is reported on flowering times in a native, species-rich, temperate grassland in Tasmania, Australia in both 2004 and 2005. • Elevated [CO2] did not affect average time of first flowering in either year, only affecting three out of 23 species. Warming reduced time to first flowering by an average of 19.1 d in 2004, acting on most species, but did not significantly alter flowering time in 2005, which might be related to the timing of rainfall. Elevated [CO 2] and warming treatments did not interact on flowering time. • These results show elevated [CO2] did not alter average flowering time or duration in this grassland; neither did it alter the response to warming. Therefore, flowering phenology appears insensitive to increasing [CO2] in this ecosystem, although the response to warming varies between years but can be strong. © The Authors (2008).