津冀3个盐渍化沼泽湿地土壤团聚体有机碳的分布特征

Distribution characteristics of organic carbon in soil aggregates of three saline marsh wetlands in Tianjin and Hebei Area

为了研究盐渍化沼泽土壤团聚体中有机碳的区域分布特征对湿地土壤碳循环的影响,选取津冀地区3个咸化沼泽湿地(北大港、七里海和白洋淀)为研究对象,分别采集表层(0~15 cm)和亚表层(15~30 cm)土壤样品,基于湿筛法得到4个不同粒级的土壤团聚体,通过酸化法去除无机碳后,对其有机碳(soil organic carbon,SOC)含量进行测定与分析.结果表明:①北大港湿地土壤表层总SOC含量显著高于七里海和白洋淀,七里海湿地亚表层总SOC含量显著高于白洋淀,但与北大港湿地无显著差异;②北大港、七里海和白洋淀湿地表层均以粒径> 0.250 mm的大团聚体为主;七里海湿地亚表层以粒径> 0.250 mm的大团聚体为主,而北大港湿地和白洋淀湿地亚表层则以粒径为0.250~2.000 mm的中间团聚体、粒径为0.053~0.250 mm的微团聚体和矿质颗粒组分为主;③北大港湿地表层土壤各粒级团聚体和矿质颗粒SOC含量显著高于七里海和白洋淀;在亚表层土壤中,北大港湿地大团聚体(> 0.250 mm)的SOC含量显著高于七里海和白洋淀大团聚体SOC的含量,而七里海微团聚体(0.053~0.250 mm)和矿质颗粒组分的SOC含量显著高于北大港和白洋淀湿地的.④土壤总有机碳和各粒级团聚体的有机碳含量与湿地植物生物量(地上、根)呈负相关关系,但与土壤盐度呈正相关关系,表明该区盐渍化梯度尽管抑制了植物生长,但增加了有机碳含量,这可能是因为该盐度梯度抑制了微生物对有机质的矿化分解,从而有利于湿地土壤有机碳的累积,说明盐渍化影响津冀地区咸化湿地土壤有机碳库分异的过程机理亟需进一步深入研究.

Studying the regional distribution characteristics of organic carbon in soil aggregates of saline marshes is vital for understanding the carbon cycle of wetland soils.Here,we selected three saline wetlands(Beidagang,BDG;Qilihai,QLH;Baiyangdian,BYD)that located in Tianjin and Hebei Province and collected soil samples from two depths(0-15 cm&15-30 cm).Soil was separated into four soil aggregate size classes using wet sieve.Soil organic carbon(SOC)contents of each fraction were measured after removing inorganic carbon.The results showed that:(1)Total SOC contents of surface layer(0-15 cm)in BDG wetland is higher than those in QLH and BYD.Total SOC contents of subsurface layer(15-30 cm)in QLH is significantly higher than BYD,whereas there is no significant difference between QLH and BYD.(2)The aggregates from>0.250 mm fraction is the majority of all wetlands;and the aggregates from>0.250 mm fraction is the majority of QLH wetlands;while midaggregates(250-2000μm)and microaggregates(0.053-0.250 mm)are the major components in BDG and BYD wetlands.(3)The SOC contents of each aggregates and mineral particle from surface layer in BDG wetland is dra matically higher than those in QIH and BYD wetlands;In subsurface layer,the SOC contents of large-aggregates(>0.250 mm)in BDG are higher than those in QLH and BYD while the SOC contents of microaggregates(0.053-0.250 mm)and mineral particles in QLH are significantly higher than those in BDG and BYD wetlands.(4)SOC contents in bulk soil and each aggregate size class were negatively correlated with plant biomass(aboveground and root),but positively correlated with soil salinity,indicating that although the salinity gradient inhibited plant growth,it increased the organic carbon content.It maybe that the salinity gradient inhibited the microbial mineralization and decomposition of organic matter,thus enhancing the accumulation of SOC in wetlands.Therefore,the mechanism of salinization-induced differentiation of SOC in saline wet-lands in Tianjin and Hebei area needs further study.