Impacts of elevated atmospheric CO2 and temperature on plant community structure of a temperate grassland are modulated by cutting frequency

To determine the impacts of climate change and defoliation on the community structure and plant diversity of a semi-natural temperate grassland, monoliths of a permanent grassland were exposed to ambient or elevated atmospheric CO2 concentrations (ambient + 235 ppmv) and temperature (ambient + VC) from October 1998 to December 2000. The monoliths were subjected to two different cutting frequencies, either two or six cuts per year. The grassland community structure changed during the course of the experiment and was more responsive to changes in management than to changes in climate. Increased cutting frequency stimulated plant diversity by enhancing the number of forb species, but plant diversity was not significantly affected by climate change. The contribution of individual plant species to the vegetation cover revealed species-specific responses to climate change and cutting frequency, but for most species significant interactions between climate change and cutting frequency were present. There were no clear-cut effects of treatments on the total annual yield and the proportion of forbs present, as significant interactions between climate change and cutting frequency occurred. It is concluded that differential grassland management will modify plant species-specific responses to climate change and resulting changes in the botanical composition of mixed-species, temperate grasslands.