Species-level effects more important than functional group-level responses to elevated CO2: evidence from simulated turves

Hanley, M.E., Trofimov, S. and Taylor, G. (2004) Species-level effects more important than functional group-level responses to elevated CO2: evidence from simulated turves. Functional Ecology, 18 (3), 304-313. (doi:10.1111/j.0269-8463.2004.00845.x).

Abstract

Using mixtures of 14 calcareous grassland plant species drawn from three functional groups, we looked at the effects of elevated atmospheric CO2 on contrasting levels of ecosystem performance (species, functional group and community). Experimental communities were subjected to ambient (?350 µmol mol?1) or elevated CO2 (?600 µmol mol?1) in controlled environments, with grazing simulated by clipping at monthly intervals for 546 days.

We assessed the effect of elevated CO2 on plant performance by quantifying the productivity (biomass) and cover of component species. We also examined the effect of elevated CO2 on the vertical structure of the plant canopy. Elevated CO2 resulted in a significant increase in total community biomass only following nutrient addition. Within functional groups, non-leguminous forb species had significantly greater biomass and cover in elevated CO2 both before and after nutrient addition, although the effect was mainly due to the influence of one species (Centaurea nigra). Grasses, in contrast, responded negatively to elevated CO2, although again significant reductions in biomass and cover could mainly be ascribed to a single species (Brachypodium pinnatum). Legumes exhibited increased biomass and cover in elevated CO2 (the effects being particularly marked for Anthyllis vulneraria and Lotus corniculatus), but this response disappeared following nutrient addition. Vertical structure was little affected by CO2 treatment.

We conclude that due to the idiosyncratic responses of individual species, the categorization of plants into broad functional groups is of limited use in guiding our understanding of the impacts of elevated atmospheric CO2 on plant communities.

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