Maximizing net ecosystem productivity: integrating chronosequence analysis and ecosystem modeling across contrasting biomes in North America

Understanding ecosystem function and dynamics is essential for crafting effective, long-term forest management strategies. Our study integrates chronosequence data, ecosystem modeling using Biome-BGCMuSo, and eddy covariance flux tower measurements to test the hypothesis that Net Ecosystem Productivity (NEP) reaches its maximum at a similar relative age across different forest types. We focused on contrasting biomes consisting of Northern Hardwoods, Douglas Fir, Jack Pine, Black Spruce and Southeastern hardwoods. Our results indicate broadly consistent NEP maximization across forest systems examined, with ecosystem modeling producing peak NEP at a relative stand age (ratio of stand age to site-specific longevity) of 0.24–0.39 and a transition to near-zero NEP between 0.46–0.86. This pattern aligns with Odum's conceptual model of ecosystem development, reflecting shifts in photosynthetic gains and respiratory losses as stands mature. Analysis combining chronosequence observations, process-based ecosystem model outputs, and eddy covariance measurements shows that NEP peaks at similar relative ages across forest types, a pattern that cannot be identified using a single approach in isolation. Sensitivity analyses under future climate change scenarios suggest that these patterns are robust to the tested range of environmental conditions. By synthesizing empirical data and process-based modeling, this analysis addresses limitations of traditional chronosequence studies, enhancing our ability to project net carbon sequestration across the complete lifespan of a stand. Our research provides model based quantitative evidence consistent with established ecological theories of forest carbon dynamics and contributes to the debate on forest carbon permanence and trade-offs in near-term climate mitigation strategies, such as harvest deferrals and stand re-establishment.