Soil Organic Carbon Stock, Source, and Stability after 20-Year Mangrove Afforestation in Southern China

Abstract

Mangrove afforestation is considered as an important measure in the “natural-based solution” for mitigating climate warming through sequestering massive carbon (C) into vegetation biomass and soil, yet how the planted mangrove species will affect soil C sequestration remains unclear. Here, we investigated the stock, source, and stability of soil organic carbon (SOC) over 1 m depth after 20-year afforestation, by planting five native mangrove species (Acrostichum aureum, Acanthus ilicifolius, Aegiceras corniculatum, Kandelia obovate and Excoecaria agallocha) on Qi’ao Island, South China. Results showed that, compared to mudflat (10.36 Kg C m-2), mangrove afforestation enhanced SOC stock by 61.29% on average without significant difference among species. Based on the two-end-member mixing model with plant-soil C stable isotope signatures, autochthonous source accounted for 59.80-87.48% of net SOC accumulation after afforestation, but varied significantly among species. Mangrove afforestation also enhanced soil light and heavy C fractions, with greater magnitudes for the latter. These findings suggest that mangrove afforestation is important to land-based efforts for mitigating climate warming by enhancing SOC stock and stability. The similar SOC stock but different source contributions among the planted species observed here may have important implications for mangrove afforestation to optimize stand structure and maximize C sequestration.

Keywords: Blue carbon, Carbon stable isotope, Mangrove plantations, Soil organic carbon factions