Net ecosystem production is similar across disturbance types in a century old North American eastern temperate forest chronosequence

Forest carbon (C) management requires an understanding of how disturbance at the time of stand establishment shapes trajectories of C pools and fluxes over successional timescales, and how the resulting secondary forests compare with undisturbed forests. In the upper Great Lakes region, fires that followed clear-cut harvesting shaped an spatially extensive cohort of forests, and the long-term C cycling implications of these fires remain poorly understood. We examined how two different stand-establishing disturbances influenced C pools and fluxes through a century of succession, comparing secondary forests with legacy late-successional stands encompassing the ages and compositions of forests that would be regionally prevalent today in the absence of stand-replacing disturbance. Our work utilized measurements taken between 2014 and 2020 from experimental forest chronosequences initiated following strictly clear-cut harvesting or clear-cut harvesting and fire, along with three >130-yr-old late successional deciduous broadleaf, evergreen needleleaf, and mixed forest functional types. We quantified soil, wood, coarse woody debris, root and other major C pools, to determine how components of the C cycle shift over time and in response to different disturbances at the time of establishment. Our findings indicate that the compounding effects of fire and clear-cut harvesting were similar to those from clear-cut harvesting alone, with the C pools and fluxes of century-old secondary forests recovering to levels comparable to two of three legacy late successional stands. The results also suggest that older legacy forests continue to serve as large sinks of C, largely through high wood production. These results indicate that fire has little bearing on the long-term magnitude and pattern of C storage recovery in Great Lakes forests.