Blue carbon stocks and wetland landscape change in the Liaohe Estuary

Introduction Coastal-wetland carbon assessments can support conservation and restoration monitoring when measured carbon pools are interpreted alongside habitat extent. This study compared carbon stocks in the dominant natural habitats of the Liaohe Estuary and examined landscape change and observations at a restoration site. Methods Natural-habitat aboveground vegetation carbon and 0-100 cm soil organic carbon were compared in a common areal unit. Exploratory Landsat classifications described landscape change during 1985-2020, and four monitoring campaigns characterized vegetation and soil conditions at a Daling River Estuary restoration site. Results Natural Suaeda salsa meadows had higher mean soil organic carbon stocks than Phragmites australis marshes (112.71 ± 49.77 versus 68.56 ± 44.62 Mg C ha⁻¹), whereas P. australis had greater aboveground vegetation carbon. Combined measured soil and aboveground stocks were 114.72 and 73.01 Mg C ha⁻¹, respectively, with soil contributing 98.3% and 93.9%. The mapped natural-wetland area contracted before an apparent increase after 2015; the unvalidated classifications provide landscape context. At the restoration site, aboveground stocks were 0.18048 and 1.833 Mg C ha⁻¹ in November 2020 and July 2022, with corresponding soil stocks of 149.08 and 163.49 Mg C ha⁻¹. Discussion The restoration-site observations differ in season and lack a concurrent unrestored reference; they therefore describe monitoring conditions rather than restoration-attributable carbon gains. The findings support protecting existing soil carbon and combining validated habitat mapping with seasonally consistent vegetation-soil monitoring.