Enhanced organic carbon burial in rewetted wetlands precedes long-term stabilization

Rewetting drained wetlands restores long-term carbon storage by reviving organic carbon burial in sediments and rebuilding carbon stocks, but the decades-long recovery pathway is uncertain. Sediment cores were dated using naturally occurring radioactive lead-210, verified with cesium-137 from past nuclear testing, to reconstruct organic carbon burial rates before drainage and for 4–40 years after rewetting across two restoration chronosequences in dry and wet climate zones; undisturbed wetlands provided benchmarks. Burial rates in undisturbed wetlands (median: 0.60 Mg C ha-1 yr-1) were comparable to pre-drainage rates in rewetted wetlands (median: 0.53), suggesting pre-drainage conditions can guide site-specific recovery targets. After ditch plugging, burial rates increased rapidly (net change: 0.28–1.01 Mg C ha-1 yr-1 within 14 years) but then declined and converged on the baseline by about 40 years. Meanwhile, total organic carbon stored in sediments rose steadily, reaching 24.6 Mg C ha-1 after four decades. Organic carbon sequestration rates in rewetted wetlands increase during early restoration and then stabilize within ~40 years, while organic carbon stocks accumulate steadily, according to radiometric dating and organic matter quantification in Canadian wetlands