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

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 CO(2) concentration ([CO(2)]) (550 mu mol mol(-1)) and warming (+2 degrees C) is reported on flowering times in a native, species-rich, temperate grassland in Tasmania, Australia in both 2004 and 2005. Elevated [CO(2)] 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 [CO(2)] 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 [CO(2)] in this ecosystem, although the response to warming varies between years but can be strong.