Genotype×elevated CO2 interaction and allocation in calcareous grassland species.

Abstract

• Biomass of genotypes of Carex flacca and Bromus erectus under CO2 enrichment was measured to test for 'winners' and 'losers' within the populations. Allocation was studied to identify reasons for varying biomass responses of the genotypes. • In a first experiment, genotypes of both species were grown separately and mown five times. In a second experiment, introducing species interaction, species were grown together (using nine genotypes of each) and harvested destructively during that time. • The first experiment showed that growth stimulation across harvests (Bromus+15%; Carex+11%) and genotype×CO2 treatment interactions in single harvests was significant, but repeated measures ANOVA was not (Carex) or only marginally significant (Bromus). Destructive harvests in the competition experiment indicated a significant growth stimulation (Bromus+28%, Carex+35%), but no CO2 ×genotype interaction was found. Similarly, ANOVA of dry matter allocation never indicated a significant CO2 ×genotype interaction. • The lack of a sustained CO2 ×genotype interaction in isolated and competitive growth conditions with good moisture supply suggests, that if there is such an interaction, it must be very small.