Plant Biodiversity and Responses to Elevated Carbon Dioxide

In

situ

studies of communities suggest that the interactions between biodiversity, atmospheric CO

2

concentration, and C cycling are very complex. Rising CO

2

will probably act on plant diversity through a number of very indirect pathways; e.g., by altering the relative availability of resources such as water and nutrients thereby altering competitive interactions among plants. Second, changes in plant community structure due to rising CO

2

concentrations, particularly in highly dynamic systems, may be as or more important in determining biomass responses than the direct effect of elevated CO

2

. Finally, species loss resulting from global change might reduce productivity as well as responsiveness to elevated CO

2

, although the response will largely depend on species identity.

Over all, simple scenarios invoking a clear and simple biospheric loop between atmospheric CO

2

and terrestrial biomass due to CO

2

fertilization need to be abandoned and replaced by an understanding of a complex system involving both biotic and abiotic feed-back loops. Our ability to either manage or predict the relationship between diversity and ecosystem function is still limited.