Distribution patterns and controlling factors for the soil organic carbon in four mangrove forests of China

Abstract

Although several studies have assessed soil organic carbon (SOC) of individual mangrove forests in China, no study has comprehensively investigated mangrove SOC and quantitatively estimated carbon sources ranging in latitude from tropical to subtropical latitudes. Therefore, this study explored the distribution patterns and factors controlling the deposition of SOC in four national mangroves nature reserves of southeastern China, specifically Yunxiao in Fujian Province, Gaoqiao in Guangdong Province, and Dongzhaigang and Wenchang in Hainan Province. Sediment core samples were collected and sectioned into subsamples to determine soil properties, including pH, salinity, moisture, bulk density, content and density of SOC, as well as carbon stable isotope ratios (δ13C). SOC contents varied with sampling sites and different mangrove communities, with 1.19 ± 0.06%, 2.52 ± 0.11%, 0.81 ± 0.101% and 4.78 ± 0.35% for Yunxiao, Gaoqiao, Dongzhaigang and Wenchang sites, respectively. Soil pH, salinity, and bulk density were negatively correlated with SOC contents at all four sites. The Yunxiao site had the highest SOC δ13C value (−25.2 ± 0.2‰), likely attributable to the severe invasion of Spartina alterniflora (a C4 plant with higher δ13C value than typical mangrove species). Significant negative correlations were also found between SOC and the δ13C values in three sites except Wenchang. Our results suggest that soil texture, dominant mangrove species and biological invasion had marked effects on SOC contents and distribution patterns of tropical and subtropical mangrove forests in China.