Abstract:

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.