Biomass accumulation and carbon storage of four different aged Sonneratia apetala plantations in Southern China

The objectives of this study were to examine plant biomass accumulation and carbon (C) storage in four different aged Sonneratia apetala plantations in the Leizhou Bay in South China. The allometric equations using diameter at breast height (DBH) and height (H) were developed to quantify plant biomass. The total forest biomass (TFB) of S. apetala plantation at 4, 5, 8, and 10 years old was 47.9, 71.7, 95.9, and 108.1 Mg ha(-1), respectively. The forest biomass C storage in aboveground (AGB) and roots at 4, 5, 8, and 10-year plantation was 19.9, 32.6, 42.0, 49.0 Mg ha(-1), respectively. Soil organic C (SOC) on the top 20 cm of sediments increased by 0.3, 6.8, 27.4, and 35.0 Mg ha(-1)after 4, 5, 8, and 10 years of reforestation, respectively. The average annual rate of total carbon storage (TCS) accumulation at 4, 5, 8, and 10-year S. apetala plantation was 5.0, 7.9, 8.7, and 8.4 Mg ha(-1) yr(-1), respectively. The TCS values in this study were underestimated because we only estimated SOC storage on the top 20-cm sediments in these plantations. This study suggests these young S. apetala plantations have the characteristics of fast growth, high biomass accumulation, and high C storage capacity, especially in sediments. They sequestrated C at a high but varying rate over time. The large-scale reforestation of S. apetala plantations in the open coastal mudflats in southern China has great potential to sequestrate more C as well as restore the degraded coastal land. The potential ecological issues associated with the increasing monoculture plantations were discussed. More long-term monitoring and research are needed to further evaluate biomass and C accumulation of S. apetala plantations over time as well as how the increasing distribution of this monoculture plantation will influence the few native mangrove remnants.