Harvested Spartina area performs better than native Scirpus in sedimentation and carbon preservation under storm surge

Abstract

Typhoons pose threats to coastal wetlands, but the impacts on carbon stocks remain unclear. This study investigated typhoon effects on salt marsh carbon pools with different vegetation covers (harvested Spartina alterniflora, native Scirpusmariqueter, bare mudflat) in the Yangtze River estuary.During Typhoon Muifa (September 2022), significant erosion occurred in the Scirpus area while the harvested Spartina area experienced sediment deposition, indicating its stronger coastal protection capacity. Grain size analysis validated the geomorphic changes. The harvested Spartina area also captured coarser sediments from the mudflat. Wave data showed the amplified hydrodynamics during typhoons can transport more sediment into marshes.In the Scirpus area, surface sediments (0–15 cm) lost 43% organic carbon and 73% belowground biomass due to erosion. The deposited sediments after typhoons lacked the original high carbon content. In contrast, harvested Spartina areas maintained carbon levels despite intense hydrodynamics. The bare mudflat lost 43% total carbon after experiencing substantial erosion.This study demonstrates harvested Spartina areas effectively mitigated carbon loss and even facilitated carbon sequestration through enhanced sediment trapping during typhoons. With intensifying storm surges, seasonal harvesting of Spartina could balance coastal protection and ecological functions better than complete removal. The carbon sink capacity of sediments with native vegetation is vulnerable to typhoons due to limited resilience. Harnessing bio-geomorphic feedbacks is crucial for preserving blue carbon storage facing climate change.