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Studies on Carbon Cycles and Bue Carbon Sinks of Chinese Mangrove Ecosystems

Carbon density,Carbon pools,Carbon sequestration,Climate Change,Human disturbance,Wetland restoration

Session 31 - Blue Carbon: from Science, Restoration and Trading

Mangrove wetlands provide numerous ecosystem services, including coast protection, fisheries production, carbon sequestration and nutrient cycling. There are increasing interests in quantifying and enhancing carbon sinks in coastal wetlands to offset carbon emission for mitigating global climate change. Although mangroves are well known for high C assimilation and flux rates, data are surprisingly lacking on whole-ecosystem carbon pools and fluxes. In addition to a huge amount of carbon in tree biomass of mangrove forests, mangrove soils consist of a variably thick, tidally submerged layer which limits litter decomposition and thus facilitate carbon storage in sediments. Limited eddy flux measurements with mangrove forests indicate that carbon fluxes of mangrove wetlands depends on not only meteorological conditions, but also tidal and salinity regimes. We have established long-term field study sites in several subtropical mangrove ecosystems with distinct climate and tidal regimes in Fujian, Guangdong and Hainan, and most of them having more than 10 year ecosystem flux observations. In addition, we have conducted field surveys on carbon stocks in the biomass and soils of mangrove forests in these provinces. There were considerable variations in carbon density in tree biomass and soils among mangrove forests of different locations and community types. Total carbon density also differed significantly among these sites. Almost all subtropical mangrove forests in China even under heavy influences of human activities showed strong carbon sink activities most time since summer 2008, with comparable ecosystem net ecosystem CO₂ exchange rates to those of a well-protected mangrove forest in Florida, USA, but significantly higher than those of nearby terrestrial forests. Implications of these results for mangrove blue carbon managements in developing countries were discussed.