潮上带盐沼地层盐分分布及形成机制

Salt distribution and formation mechanism in supratidal saltmarsh stratum

为了探究潮上带盐沼系统地层盐分分布规律及其形成机制,本研究以江苏盐城近岸盐沼湿地为例,采用电阻率测量和土壤样品分析的方法,得出土壤孔隙水盐度空间分布,并分析其与生态地貌类型的关系。结果表明,盐沼平台10 m深度以下地下水盐分较高且空间分布均匀,5 m深度以上浅层孔隙水存在显著淡化,其程度与条带状生态地貌特征相关;近潮沟区域浅层土壤孔隙水盐度接近海水,而螃蟹孔洞和互花米草区域下方地层均存在低盐区,且前者规模更大;短期潮汐过程仅影响近潮沟区域的局部地层盐分,螃蟹孔洞明显促进了降水的下渗和脱盐作用,并有助于地表蒸发和盐分集结,增大了浅层土壤水盐度的垂向差异,而植被生长引起的根系优势流和蒸发抑制作用,有效降低了表层土壤的盐度水平。

To explore the distribution pattern and formation mechanism of salt in the stratum of supratidal saltmarsh system,the coastal saltmarsh wetland in Yancheng,Jiangsu Province,was considered in this study.The spatial distribution of soil porewater salinity was obtained through resistivity measurement and soil sample analysis,and the corresponding relationship with ecogeomorphology was further revealed.As a result,the groundwater salinity below the depth of 10 m is relatively high and uniformly distributed,while shallow porewater above 5 m depth is significantly desalinated.The degree of porewater desalination is related to the characteristics of zonal ecogeomorphology.Salinity of shallow porewater in the near-creek area is close to that of seawater.However,the shallow stratum underneath the crab hole area and Spartina alterniflora area has much lower salinity,with the former presenting a larger spatial scale.The short period tidal process only affects the localized salinity near the tidal creek.The crab holes significantly promote the infiltration of rainwater and its desalination effect,and contribute to near-surface evaporation and salt accumulation,increasing the vertical difference of shallow soil water salinity.The root preferential flow and evaporation inhibition caused by vegetation growth effectively reduce the salinity level of surface soil.