11 - Effects of Elevated CO2 on Plant Species Dominance in a Highly Diverse Calcareous Grassland

Abstract

This chapter focuses on the difficulties in detecting and predicting the changes in community structure caused by CO2. The chapter also discusses the usefulness and limitations of plant species manipulations for gaining additional insight into the potential effects of changes in the plant community structure on the ecosystem function. Calcareous grasslands were chosen for this study because they are some of the most species-rich temperate ecosystems and they are disappearing due to altered land use and management practices. This experiment addresses the main problems associated with aggregating species into functional groups for the purpose of predicting changes in ecosystem function in response to changes in community structure. Elevated CO2 does not detectably increase aboveground plant biomass in natural or artificial calcareous grassland communities in the first year of exposure. Variation exists in the response of individual species or groups of species to elevated CO2 in experiments with calcareous grassland species, and this variation may lead to changes in species dominance. Aboveground plant biomass is affected by plant community composition. This is attributed to changes in plant species number but may also be due to other factors such as species identity and differences in the initial conditions.