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Changes in carbon storage in inland saline-alkalined wetlands.

Wetlands have the ability to sequester atmospheric carbon into peat or soil organic matter. They represent the largest component of the terrestrial biological carbon pool and may exert a large influence on global carbon cycles because they store about one-third of the global terrestrial soil organic carbon (1,395 Gt [3.07 x [10.sup.15] lb]). Although much attention has been given to the role of freshwater wetlands as carbon sinks, particularly northern peatlands, changes in carbon storage in the many small, scattered salt marshes, especially inland saline-alkaline wetlands are poorly known. Carbon cycles in wetland ecosystems are regulated by a series of interacting processes between soil, hydrology, and vegetation, of which hydrology is probably the single most important determinant of ecological processes because its shifts or fluctuations can lead to soil organic matter decomposition or accumulation in wetlands.

Erbaifangzi (an open wetland, open to hydrologic fluxes with other systems) and Fulaowenpao (a closed wetland, isolated from hydrologic fluxes with other systems) were chosen as two typical sites in the Xianghai wetland, one of the "wetlands of international importance" in northeastern China. We compared soil organic carbon content of both types of saline-alkaline wetlands with different hydrological conditions and determined the relationship between soil organic carbon contents and soil properties of wetlands. Soil properties such as total nitrogen, total phosphorous, soil pH, carbon/nitrogen, soil particle size, and bulk densities were also analyzed in order to identify their relationship to soil organic carbon stocks. We observed higher soil organic carbon contents in the open wetland due to waterlogged or wetter hydrological conditions compared with the drier, closed wetland. The mean soil organic carbon storage of the open wetland with the depth of 1 m (1.094 yd) was about about 41% higher than that of the closed wetland. Therefore, the hydrological regime can be considered an important influencing factor for carbon stocks in wetland soils. Soil organic carbon generally decreased with depth in soil profiles from both sites and is mainly stored in the upper 30 cm (11.81 in), accounting for more than 50% of the total, which is closely linked to plant litter, root distribution, rhizodeposits and flood deposition. We also found soil organic carbon storage was significantly affected by such soil properties as soil organic matter, total nitrogen, total phosphorus, soil pH value, and soil texture.

The two inland saline-alkalined wetlands studied have much lower soil organic carbon contents than those in other wetlands in China, even lower than the global average soil organic carbon content in salt marshes, which is closely linked to dry climate and water deficit in this region. In addition, the planned building of the Baiyunhua reservoir upstream of the Huolin river will also be a potential threat for the downstream wetlands facing serious water shortage. Ecological water supplement--that is, water supplement based on ecological water requirements for preserving ecosystem health--may be necessary to mitigate water shortage and increase carbon storage of wetlands in semi-arid and arid regions such as this.

For more information see the full paper on pages 447-452 of this issue (Bai et al. 2007).


Bai, J., B. Cui, W. Deng, Z. Yang, Q. Wang, and Q. Ding, 2007. Soil organic carbon contents of two natural inland saline-alkalined wetlands in northeastern China. Journal of Soil and Water Conservation 62(6):447-452.
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Author:Bai, Junhong
Publication:Journal of Soil and Water Conservation
Article Type:Report
Geographic Code:1USA
Date:Nov 1, 2007
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