江汉水生植物群落的结构与数量特征

汉江是长江的第一大支流，是我国实施南水北调工程的重要对象。目前，有关汉江水生植物群落方面的研究尚未见报道。因此，在1998-2000年，运用植物群落学研究的理论和方法，对汉江沿途6个江段水生植物群落的结构和数量特征进行了定位研究。在汉江上游与下游各江段，群落水平分布格局为斑块状，不象湖泊或池塘系统那样表现出明显的均匀分布或带状分布特征，而在中游局部江段中表现为小范围的带状分布。群落垂直分布格局，在上游江段，以沉水层为主，浮叶层和挺水层不发达或缺乏；在中游各江段，群落表现出完整的垂直结构层次：挺水层、漂浮层、浮叶层和沉水层；在下游江段群落结构常为两层或一层结构，以浮叶层和挺水层为主，而沉水层在下游江段发育不充分且生物量很小。另上，对汉江上、中、下游的典型植物群落的数量特征进行了分析。研究表明，在汉江的不同江段，群落的组成、结构和数量特征等都不同，而水位、流速、基质状况、人为干扰是影响汉江水生植物群落生长和分布格局的主要因子。

STRUCTURE AND QUANTITATIVE FEATURES OF AQUATIC PLANT COMMUNITIES IN THE HANJIANG RIVER

The Hanjiang River is not only the largest tributary of the Yangtze River, but also the most important objective enforced by the project of transferring water from South_China to North_China. Research about aquatic plant communities has not yet been reported. During the period of 1998_2000, theories and methods about plant community researches were adopted and field studies on the structure and quantitative features of aquatic plant communities were carried out in six cities along the Hanjiang River. The results indicated that the horizontal structure of communities in the upper and lower reaches of the Hanjiang River showed a patchy distribution which differed from the apparent uniform or strip distribution in lake or pond systems. The vertical structure of the biomass of communities in the upper reach was mainly focused in the submerged layer, while the floating layer and emergent layer were often undeveloped or lacking. However, in the middle reach the communities usually showed a complete and developed vertical structure. In the lower reach there were only one or two layers, and the biomass of communities was mainly concentrated in the floating layer or emergent layer. The submerged layer was comparatively undeveloped and contributed little to the communities' biomass. In addition, the quantitative features of communities were analyzed. The study showed that the composition, structural developments and quantitative features of the community were significantly different with each spots. Water level, water flow, the characteristics of substrates, and human interference were regarded as the main factors that resulted in the difference of distribution patterns and growth form of the communities.