Functional Role of Mangrove Forests Along the Subtropical and Tropical Coasts of China

Abstract

Mangroves forests inhabiting the south coast of China are crucial habitats for the functioning of the coastal zone. This role has not been carefully considered in China and compared to their functional role worldwide. China’s mangroves currently occupy 20,303 ha. Average forest biomass is equivalent to the global average, but the mean ratio of below-ground to above-ground biomass is high (46%), reflecting the young age of most forests. Rates of annual litterfall, net primary productivity, and root production are above the global average, indicating that China’s mangrove forests are highly productive within their latitudinal band. High productivity may reflect high rates of organic inputs, young forest ages, and high rates of precipitation. As China’s mangrove forests have short canopies, these data imply that the rates of forest turnover are more rapid than in most other mangroves. Mangrove organic carbon (C<sub>org</sub>) stock averaged 190.96 Mg C<sub>org</sub> ha<sup>-1</sup>, mostly (58%) in soils, less than the global average, reflecting young forest age and frequent soil disturbance. Total C<sub>org</sub> stored in China’s mangroves is 3.9 Tg, only 0.03% of the global total, but the total C<sub>org</sub> sequestration rate is 139.4 Gg C<sub>org</sub> a<sup>-1</sup> while the average C<sub>org</sub> sequestration rate is 6.87 Mg C<sub>org</sub> ha<sup>-1</sup> a<sup>-1</sup>, which is greater than the global average. C<sub>org</sub> losses via microbial mineralization are large as total C<sub>org</sub> export from mangroves accounts for 44% of the total C<sub>org</sub> exported to the South China Sea. Nutrients are efficiently retained suggesting their use and proper management as aquaculture filters. Mangroves have close links to other coastal food webs.