Revisiting the Role of Biological Nitrogen Fixation in Forest Recovery Under Global Environmental Change

Classical ecosystem theory depicts biological nitrogen fixation (BNF) as a mechanism that replenishes disturbance-driven nitrogen (N) losses, thereby alleviating N limitation and facilitating ecosystem recovery. These assumptions persist in present-day theories, models, and applications. However, disturbance regimes and environmental conditions have changed dramatically since the formation of the original BNF theories, motivating a new evaluation of the role of BNF. Focusing on forests, we find evidence that disturbance effects on BNF range from net positive to net negative and that current BNF fluxes have a limited capacity to replenish N losses if disturbances become more severe and frequent, or if they create conditions that suppress or constrain BNF. The subsequent effects of BNF on ecosystem recovery also vary. N-fixing trees and shrubs can have positive to negative effects on the recovery of carbon stocks, and under novel disturbance regimes they may alter, and even impede, forest succession. We present an updated view of BNF–recovery relationships in forest ecosystems undergoing global environmental change.