Elevated CO2 responsiveness, interactions at the community level and plant functional types

Plant responsiveness to elevated carbon dioxide (CO2) is a relevant dimension for the definition of functional types in the face of global change. Most traits reported to be associated with high CO2 responsiveness are derived from laboratory experiments on individually grown species. This paper suggests that physiological traits such as photosynthetic pathway and internal sink strength are necessary, but not enough for the prediction of plant responses in mixed stands. A number of examples from the literature are presented to illustrate how predictions based on single-species experiments may not match the behaviour of multi-species assemblages. Individual attributes associated to the interaction of the species with other members of the community should be also considered. Morphogenetic and architectural traits, as well as characteristics related to other trophic levels, such as the presence of root symbionts or the preferential allocation to growth or defences against herbivory, may be useful for a better prediction of plant responsiveness to high CO2 in the field.