长江口崇明岛周缘盐沼湿地土壤碳储量的空间格局

盐沼湿地在缓解温室效应和应对气候变化方面发挥着重要作用,是重要的"蓝碳"生态系统。储存在盐沼湿地土壤中的有机碳(SOC)是盐沼湿地碳汇的主要成分,但受植被覆盖、土壤环境等生境要素变化的显著影响。以长江口崇明岛周缘的盐沼湿地为典型研究区域,分别测量了环岛不同样线和不同植被区SOC含量及环境因子(盐度、容重、碳氮比(C/N)等),在此基础上分析了盐沼湿地SOC储量的空间分布格局及其影响因素。结果表明:(1)崇明岛周缘盐沼湿地SOC含量和储量均存在明显的空间异质性,北侧的土壤SOC含量高于南侧,东北侧的SOC储量高于西南侧区域;(2)垂直各层上,SOC含量呈现随土层深度增加逐渐减少的趋势,表层0-50 cm深度的单位面积SOC储量大于50-100 cm深度;(3)植物类型和土壤理化因素(土壤C/N、土壤盐度、土壤容重等)在一定程度上影响了崇明岛周缘盐沼湿地土壤碳储量的空间格局。研究表明,受河口区植被和土壤理化性质等多种因素空间异质性的共同影响,盐沼湿地土壤SOC储量格局也易呈现空间差异,因此在开展盐沼湿地储碳机制研究、科学评估盐沼湿地储碳能力及实现盐沼"蓝碳"固碳增汇时应充分考虑区域间的环境和生态的空间异质性特征。

Spatial pattern of soil carbon storage in salt marsh wetlands around the Chongming Island in the Yangtze River Estuary

Salt marsh wetlands are regarded as important blue carbon ecosystems, which play important roles in mitigating the greenhouse effects and resist global climate change. Organic carbon stored in the soil (soil organic carbon, SOC) is the main component of the carbon sink in salt marsh wetlands, but its storage is susceptible to various environmental factors. The changes of environment factors, such as vegetation coverage and soil physicochemical factors, could significantly affect the SOC storage capacity of salt marsh wetlands and change the spatial distribution of soil carbon storage, especially in estuarine area where there are obvious spatial and temporal differences in environment. Based on the salt marsh wetlands around the Chongming Island in the Yangtze Estuary as a typical study area, the SOC content of different line transects and different vegetation types along the elevation change from sea to land were measured around the island, and the physicochemical properties of plants and soil (salinity, bulk density, C/N ratio, etc.) at each sampling point were monitored simultaneously. Besides, the spatial distribution pattern of SOC storage in the salt marsh wetland around the Chongming Island and its influencing factors were analyzed. The results showed that: (1) there was significantly spatial heterogeneity in the SOC content and storage in the salt marsh wetland around the Chongming Island, with higher SOC content on the north side and higher SOC storage on the northeast side. (2) on the vertical soil layers, the SOC content showed a decreasing trend with the increase of soil depth, and the SOC storage per unit area at 0-50 cm depth was higher than that at 50-100 cm depth. (3) plant types and soil physicochemical factors (soil C/N, soil salinity, soil bulk density, etc.) regulated and interacted with each other, which affected the spatial pattern of the SOC storage in the salt marsh wetlands around the Chongming Island to some extent. Studies have shown that, due to the spatial heterogeneity of vegetation types and soil physicochemical properties in estuaries, the SOC storage patterns in salt marsh wetlands were also prone to spatial variation. Therefore, the spatial heterogeneity of the environment and ecology between regions should be fully considered when carrying out the investigation of carbon storage, which not only helps to scientifically evaluate the carbon storage capacity of salt marshes, but also will be of great significance to further explore the carbon storage mechanism of salt marshes and implement the carbon sequestration and sink increase of blue carbon in the salt marshes.