崇明东滩湿地土壤有机碳空间分异特征及影响因素

Spatial Variability of Organic Carbon in the Soil of Wetlands in Chongming Dongtan and Its Influential Factors

为了解不同类型湿地土壤有机碳含量的空间分异特征,以长江口崇明东滩不同植被类型和冲淤性质的湿地土壤为研究对象,测定3种土壤中有机碳含量、微生物量、以及与碳代谢相关的土壤酶活性,分析不同类型湿地土壤有机碳含量的空间变异特征,并对其影响因素进行了讨论。结果表明,不同类型湿地土壤的有机碳含量在不同潮间的变化趋势基本一致,呈现出高潮滩>中潮滩>低潮滩>光滩,即高潮滩具有较强的有机碳汇聚能力。3种不同类型湿地土壤有机碳含量的空间变异性较大,其特征表现为:芦苇型沙质土-A区([4.34±1.30)g·kg-1]<芦苇/互花米草混合型粘质土-B区([7.35±1.63)g·kg-1]<芦苇/互花米草型粘质土-C区([9.17±1.18)g·kg-1],A区有机碳含量空间变异系数最大为52%,C区最小为22%,而且有机碳空间分异受湿地土壤微生物数量、酶活性以及土壤含水、含盐量的影响。芦苇型沙质土-A区有利于微生物的呼吸、代谢与繁殖,具有较高的有机碳代谢能力,而芦苇/互花米草型粘质土-C区则更有利于有机碳的保留。研究结果用于阐明不同类型湿地土壤的有机碳保留能力,进而为湿地的管理与优化提供理论基础和决策依据。

Organic carbon content reflects the carbon accumulation capability of wetland soil. For clarifying difference of different types of wetland soils in carbon accumulation capability, three types of wetland soil with different vegetations and erosion/deposition properties（located at southeast, northeast, and north of Dongtan, respectively ） were choose to study the spatial variability of organic carbon content of wetland soil in Chongming Dongtan, and the factors resulting in the difference were discussed from the view points of the microbial activity and envi- ronmental conditions. The results showed that from high tide beach to light beach, the changing trend of organic carbon content of different types wetlands soil was similar, that presented a high tide beach〉 in the tidal flats〉 low beach〉 light beach due to the decrease of organic matter input from vegetation death accordingly. However, the average contents of organic carbon in different types of wetland soil had the large spatial variability, which was characterized by ： Phragmites australis -sandy soil （ southeast-A area ） （ 4.34± 1.30 ）g· kg^-1〈 Phragmites australis/Spartina alterniflora-clay soil （ northeast-B area） （ 7.35± 1.63 ）g· kg^-1〈 Phragmites australis/Spartina aherniflora-clay soil （north-C area） （9.17±1.18 ）g· kg^-1. The maximum and the minimum space variation coefficient of organic carbon content were 52% in A area and 22% in C area, respectively. The result also showed that the difference of microbial biomass, soil enzyme activity, moisture and salt content among these soils might be the important reasons resulting in the spatial variation of organic carbon content. The Phragmites australis-sandy soil （southeast-A area） was suitable for microbial metabolism and propagation, hence higher organic carbon decomposition capability, whereas the Phragmites australis/Spartina alterniflora-clay soil（ north-C area ） was more beneficial to reserve organic carbon due to its lower microbial activity. The experimental results will provide a useful aid for managing wetland to optimize its eco-function.