STUDIES ON THE DIVERSITY OF AQUATIC PLANTS IN HANJIANG RIVER

The species compositions, distribution and biodiversity of aquatic plants in 13 belt transect along Hanjiang River have been surveyed in two years'field studies. There were 54 species of aquatic plants belonging 36 genera and 26 families in Hanjiang River.The index of H, D and R showed that the up-down-up three folded to four folded changing tend from the Hanzhong spot on the upper reaches to the Hankou spot on the lower reaches. Along the gradient of water depth and horizontal distance from upper to lower reaches of Hanjiang River, βdiversity showed the result of βlowerβupperβmiddle, indicating higher habitat heterogeneity in the lower reach than in the upper and middle reaches. γdiversity showed γupperγmiddleγlower. While among spots, γdiversity was the highest in Laohekou spot(29 species). The next were at Danjiangkou spot and Xiangfan spot, and the lowest value was at Hankou spot. In summary, aquatic plants were rich in middle reaches of Hanjiang River where water was clear and low in the lower reaches due to water pollution and human disturbance.