Steeper declines in forest photosynthesis than respiration explain age-driven decreases in forest growth

Abstract

Advancing our understanding of how and why forests dynamically change in their productivity is important to predict the future change. The traditional view of forest dynamics originated by Kira, Shidei, and Odum suggests a decline in net primary productivity [or gross primary productivity (GPP) − autotrophic respiration (Ra)] in aging forests due to stabilized GPP and continuously increased Ra. We found that, in contrast to the traditional view, both GPP and Ra decline in aging forests while GPP decreases more rapidly than Ra does, and thus generalize the alternative hypothesis initiated by Ryan and colleagues with a large dataset. We presented a new quantitative model to describe forest dynamics that can be incorporated into ecosystem models.