滨海盐沼盐地碱蓬根部凹坑微地形结构的形成机理研究

Formation mechanism of concave microtopography at the root of Suaeda salsa in the coastal salt marsh

植被在潮汐作用下能够改变滨海湿地中微地形结构,微地形结构的改变则会影响生态系统的结构、过程和功能。了解植被在潮汐作用下改变微地形结构的作用机理,对于开展滨海湿地的生态保护与修复具有重要指导作用。本研究通过野外调查和模拟实验研究了黄河三角洲滨海盐沼湿地中盐地碱蓬植株根部凹坑微地形的形成机理。研究结果表明:随着盐地碱蓬植株从幼苗到成株的不断成长,植株的茎秆强度也不断增强,在潮汐作用下其根部形成的凹坑微地形的直径和深度也不断增大。高茎秆强度的模拟材料硬竹签根部的凹坑微地形的直径和深度也显著高于低茎秆强度的软塑料条。随着由海向陆受潮汐影响的盐沼区域高程的不断增高,盐地碱蓬植株及茎秆模拟材料根部的凹坑微地形的直径和深度也不断增大。在受潮汐影响范围内的盐沼区域中,植株及茎秆模拟材料根部凹坑微地形的直径和深度都与土壤盐度、土壤硬度以及土壤p H呈正相关关系,都与土壤含水率、潮汐侵蚀速率、泥沙沉积速率、平均日淹水频次、平均最大淹水水深以及平均日淹水时长呈负相关关系。

Vegetation can change the structure of microtopography under tidal action in coastal wetlands,and the change of microtopography could affect the structure,process and function of ecosystem. Understanding the effect mechanism of vegetation on microtopographic structure is of importance to undergo protection and restoration based on ecosystem process in coastal ecosystems. Field surveys and simulation experiments were conducted to investigate the formation mechanism of concave microtopography at the root of Suaeda salsa in a coastal salt marsh ecosystem,in the Yellow River Delta,northern China. Results showed that with the growth of Suaeda salsa from seedling to mature plant,the stem strength of plants significantly increased,and the diameter and depth of the concave microtopography at the root of the plants also significantly increased. The diameter and depth of the concave microtopography at the root of the hard bamboo stick( stem imitated material) with high stem strength were significantly higher than those at the root of soft plastic stick( stem imitated material) with low stem strength. With the increasing elevation of the salt marshes affected by tides from the sea to the land,the diameter and depth of the concave microtopography at the root of the plants and stem imitated materials also increased. In salt marsh zones affected by tides,the diameter and depth of the concave microtopography at the root of the plants and stem imitated materials were positively related to soil salinity,soil hardness and soil p H,and negatively related to soil moisture content,tidal erosion rate,sediment deposition rate,average daily flooding frequency,average maximum daily flooding depth,and average daily flooding duration.