湛江高桥红树林表层沉积物的粒度空间分布特征

红树林湿地是滨海湿地的一个重要类型,也是重要的沉积库.沉积物是红树林定居与生长的基质,记载着红树林湿地的环境历史,可用于物源分析和沉积过程反演,对于红树林湿地的生态恢复和保护具有重要意义.2011年7月,以湛江国家级红树林自然保护区高桥片区红树林湿地为研究区,沿着水动力梯度进行取样,并基于沉积物粒度分析其表层沉积特征,通过地统计学方法生成预测表面,并结合有机质含量和群落结构进行相关性分析.结果表明:研究区沉积物是以粘、粉粒为主的混合沉积类型,砂粒、粘粒和粉粒平均含量分别为(27.8±15.4)%、(40.3±15.4)%和(32.1±11.4)%;表层沉积特征呈现明显的空间梯度,随着与陆地距离增加,从高潮位到低潮位方向上,沉积物砂粒含量增加,粘粒含量降低.表层沉积的有机质与粉粒含量呈正相关,而与砂粒呈负相关,且在水动力条件弱的高潮位区域,有机质含量高.表层沉积特征在不同群落生境间存在差异,沉积特征与不同红树林群落结构存在一定程度的相关性,反映了水动力条件与红树林之间的复杂关系.

Spatial characteristics of grain size of surface sediments in mangrove wetlands in Gaoqiao of Zhanjiang,Guangdong Province of South China

Mangrove wetland is an important type of coastal wetlands,and also,an important sediment trap.Sediment is an essential medium for mangrove recruitment and development,which records the environmental history of mangrove wetlands and can be used for the analysis of material sources and the inference of the materials depositing process,being essential to the ecological restoration and conservation of mangrove.In this paper,surface sediment samples were collected along a hydrodynamic gradient in Gaoqiao,Zhanjiang Mangrove National Nature Reserve in 2011.The characteristics of the surface sediments were analyzed based on grain size analysis,and the prediction surfaces were generated by the geo-statistical methods with ArcGIS 9.2 software.A correlation analysis was also conducted on the sediment organic matter content and the mangrove community structure.In the study area,clay and silt dominated the sediment texture,and the mean content of sand,silt,and clay was(27.8±15.4)%,(40.3±15.4)%,and(32.1±11.4)%,respectively.The spatial gradient of the sediment characteristics was expressed in apparent interpolation raster.With increasing distance from the seawall,the sediment sand content increased,clay content decreased,and silt content was relatively stable at a certain level.There was a positive correlation between the contents of sediment organic matter and silt,and a negative correlation between the contents of sediment organic matter and sand.Much more sediment organic matter was located at the high tide area with weak tide energy.There existed apparent discrepancies in the characteristics of the surface sediments in different biotopes.The sediment characteristics had definite correlations with the community structure of mangroves,reflecting the complicated correlations between the hydrodynamic conditions and the mangroves.