CO₂ elicits long-term decline in nitrogen fixation

Hungate et al investigate the effects of elevated atmospheric carbon dioxide (Ca) on legume nitrogen fixation in a stand of scrub-oak vegetation in central coastal Florida, where the leguminous vine Galactia elliottii Nutt occurs naturally. They found that experimental Ca exposure initially increased but later suppressed N fixation, contrary to the expected response. Biogeochemical feedbacks can substantially modify ecosystem responses to global change, and their results underscore the need to broaden the suite of elements typically considered when examining these feedbacks.