苏北滨海湿地不同植被带沉积物粒度特征分析

Characteristics of Grain-size Distributions in Different Vegetation Zones of Coastal Wetland in North Jiangsu

在新洋港滩涂上由海向陆设置断面,共采集8个沉积物柱状样（0-40 cm）和14个表层土样（0-20 cm）并对其进行粒度分析,以探讨新洋港滨海湿地沉积物的粒度分布特征以及植被对沉积物分布的影响。结果表明：1）光滩沉积物粒径（4.60）明显大于各个植被带（5.10-5.78）,各植被带间粒径无明显变化。在互花米草滩沉积物颗粒迅速变细,分选变差。2）光滩沉积物中砂和粉砂分别占34%和56%,粘土极少,互花米草滩沉积物中砂降至5%,粉砂和粘土分别增加至70%和25%,互花米草滩成为植被演替序列中沉积物粒度参数的突变点。3）植被发育演替改变了潮滩表层沉积物粒度分布格局,对水动力条件和沉积物沉积过程具有明显的改造作用。随着植被类型和滩面高程变化,沉积物粒度分布特征也相应发生变化。4）光滩、互花米草滩沉积物在垂直方向上粒度参数变化较大,盐碱滩和芦苇滩垂直方向上无明显变化。潮流作用、潮滩不同部位的水动力差异以及不同植被的作用是造成垂直方向粒度特征差异的主要原因。

8 sediment cores （0-40 cm long） and 14 top soil samples （0-20 cm long） were collected landward along a section designed in the Xinyanggang tidal flat and the grain size of these samples was analyzed in order to discuss the grain-size distribution characteristics in Xinyanggang coastal wetland and the influences of vegetations to the sediment distributions. It has been indicated that 1） in the bare flat the grain size （4.60 φ） of the sediments is distinctly coarser than those （5.10-5.78 φ） in all vegetated zones, where the grain size changes little between each other, whereas in the flat growing with Spartina alterniflora the sediments change to fine-grained quickly and their sorting becomes poor; 2） in the bare flat the sediments contain 34% of sand, 56% of silt and very little of clay, whereas in the sediments of the flat growing with Spartina alterniflora sand decreases down to 5% and silt and clay increase to 70% and 25% respectively. The flat growing with Spartina alterniflora becomes a break spot in grain-size parameters in the vegetation succession; 3） The vegetation development and succession changed the grain-size distribution patterns of the surface sediments in the tidal flat and also exerted distinct influences to hydrodynamics and deposition processes. With changing in vegetation type and flat elevation, the grain-size distribution patterns of sediments can also vary correspondingly; 4） The sediments in the bare flat and the flat growing with Spartina alterniflora change greatly in grain-size parameters in the vertical direction, whereas those in the salt marsh and the flat growing with reed have no distinct changes. The tidal current, the variations in hydrodynamics at different parts of the tidal flat and the differences in vegetations may possibly be the main reasons that caused the vertical variations in grain-size distributions.