Soil Organic Carbon Sequestration after 20-Year Afforestation of Mangrove Plantations on Qi’ao Island, Southern China

Mangrove afforestation is considered an important measure in the “natural-based solution” for mitigating climate warming through sequestering massive carbon (C) into vegetation biomass, yet how planted mangrove species facilitate soil C sequestration remains unclear. Here, we investigated stock, source, and fraction of organic (SOC) over 1 m depth after 20-year five pure plantations (Acrostichum aureum, Acanthus ilicifolius, Aegiceras corniculatum, Kandelia obovate, Excoecaria agallocha) on Qi’ao Island, South China. The results showed that SOC stocks did not significantly differ among plantations, with average value 16.7 kg m−2. Based two-end-member mixing model plant–soil stable isotope signatures, autochthonous (mangrove-derived) source accounted 20.2–34.1% but varied plantations. stock particulate (1.2–2.0 g kg−1) mineral-associated (14.3–16.0 also differed similar different contributions fractions observed here may have implications to optimize stand structure maximize sequestration.