卵石河床中底栖动物垂向分布特征及影响因素

Parameters influencing the vertical distribution of macroinvertebrates in a gravel bed

研究底栖动物在河床底质中的分布特点,对认识河流潜流层生态具有重要意义。该文通过人工设置垂向分层栖息地的试验方法研究了不同粒径底质中底栖动物的物种丰度、密度及综合多样性水平(用改进Shannon-Wiener多样性指数表征)沿底质垂向深度的分布特征。试验结果表明:底栖动物入住新生栖息地时至少需要6周达到稳定的群落结构。物种丰度和密度随深度波动减小,这与不同功能摄食类群的物种对不同底质深度具有偏好性有关。底质粒径也对底栖动物的多样性具有一定的影响。表层底质中,中值粒径为2cm的卵砾石底质能够为底栖动物提供最多的适宜的微栖息地空间,从而其中综合多样性水平最高。而深层底质中,中值粒径为5cm左右的卵石底质更易于创造最高的综合多样性水平。

The vertical distribution of macroinvertebrates in a river bed is needed to understand the hyporheic ecology.In this study artificially organized multi-layer gravel habitats were used for macroinvertebrate colonization and for the systematic study of the vertical distributions of the taxa richness,density,and the integrated biodiversity level（indicated by the improved Shannon-Wiener index） of macroinvertebrates.The experimental results indicate that the macroinvertebrates need at least 6 weeks to colonize and form a stable community in the new habitats. The taxa richness and macroinvertebrates density fluctuated some,but mainly decreased from the bed surface to the bed depth of 40 cm possibly because different functional feeding groups prefer different bed depths.That is,some species live on the bed surface,while others inhabit deeper levels.The bio-diversity of the macroinvertebrates was also related to the grain size of the substrates.At the bed surface,the substrate consisted of small gravel（D50 =2cm）supporting the most suitable micro-habitat for macroinvertebrates and,therefore,the highest integrated bio-diversity level.However,deeper in the bed,the substrate consisted of median size gravel（D50 =5cm）which tended to create the highest integrated bio-diversity level.