PNNL

Abstract

Global forests are increasingly exposed to climate-driven perturbations, which may in turn alter the climate mitigation potential of forests. As tropical cyclones expand poleward due to climate warming, wind disturbances in temperate forests have become more frequent. The consequences of moderate wind disturbances remain poorly understood, however, which hinders the quantification of the role of disturbances in the global carbon cycle. Here, we used 16-year continuous measurements with eddy covariance and biometric methods to investigate the impacts of moderate wind disturbances on the structure and carbon sink of a natural secondary temperate mixed forest. Following Typhoon Maysak in 2020, the mortality of large trees (particularly the aging pioneer species) increased by nine times, but that of small trees decreased by nearly half. Both stand basal area and leaf area index were reduced between 2019 and 2023, with aging pioneer tree species more vulnerable than mid-to-late shade tolerant species to wind disturbances. Shifts in species composition altered the environmental sensitivity of forest carbon sink functions. Unexpectedly, wind disturbances reversed the declining trends in net ecosystem production and ecosystem carbon use efficiency (CUE) of this secondary forest. A novel composite structural indicator—the standardized leaf area index (the maximum leaf area supported by per basal area of the stand)—provides robust predictions (R2 > 0.4) of carbon sink dynamics throughout the study period. The selective removal of less efficient pioneer trees accelerated succession and reversed the aging-related decline in forest carbon sink and CUE. These findings highlight the potential role of moderate wind disturbances in enhancing forest carbon sink function and inform a framework for understanding, assessing, and predicting forest carbon dynamics under increasing disturbance frequencies driven by climate change.