Characteristics Of Riparian Plant Communities In Mountainous Rivers Affected By Hydropower Development

Recently,significant attention has been paid to the impact of cascade hydro-power development on river ecosystem in mountainous rivers.As renewable energy exploration,hydro-power development introduced a series of direct or indirect impacts on plant diversity in riparian zone.In order to fully understand the impact of hydropower development on the diversity of riparian plant communities,the cascade hydropower development in Dicun River basin,a tributary of Jiulongjiang River basin,was selected for study.From the source of Dicun river basin to the estuary,nine sampling plots are chosen successively(i.e,the source of Dicun River Stream,sites of Piliao,first-class dam,first-class power station,second-class dam,second-class power station,third-class dam,third-class power station and estuary).Based on the quantitative analysis of herbaceous plant communities in riparian zone and the assessment upon vertical and transverse plant community diversity along the riparian zone,the effects of hydro-power development on plant communities and plant diversity in riparian zone in mountainous rivers were discussed,to minimize the adverse effects of cascade hydro-power development,protecting the plant diversity along the riparian zone,and fully maximizing the advantages of hydro-power development.The core findings obtained in this thesis were shown:(1)Cascade hydro-power development has a great impact on the runoff of downstream river.During operation of the hydro-power station,a waterreducing reach was formed between the dam and the downstream powerhouse,which expressed inevitable impact upon hydrological conditions of the basin.In addition,the environmental factors such as river width and river velocity have also changed significantly.Hydro-power development has resulted in the fragmentation of river habitats,seriously affecting the physical and hydrological characteristics of the River and the distribution pattern of water resources.(2)Through the investigation and study of the riparian herbaceous community,the considerable change of environmental humidity gradient was reflected.There was a corresponding relationship between community and environmental factors among herbaceous plant communities.Elevation gradient,bank and river width and flow velocity are important environmental factors affecting plant spatial distribution.There were great differences in adaptability and tolerance of each species to environmental factors.(3)From the perspective of the dominance and evenness of plant communities,the diversity level of plant communities in the watershed was low,and the diversity of plant communities varie d greatly among different plots.Apparently human disturbance was the most important factor affecting the diversity of plant species in the region.The combination of natural and human factors determined the regional characteristics of plant diversity in the Dicun river basin watershed.(4)Hydro-power development resulted in significant changes in environmental factors such as river width,water depth an d flow velocity,and changes in altitude.Furthermore,river width and flow velocity also had an impact upon species diversity,but not sufficiently significant.Inevitably,human disturbance was the dominant factor in the variation of plant diversity in the riparian zone of Dicun River basin.There was a significant positive correlation between plant richness index and flow velocity in various types of riparian zones(P < 0.05),and a significant negative correlation between plant evenness index and flow velocity(P < 0.05).(5)This thesis evaluated the river health of Dicun river basin based on the method of entropy weight.The results show that the river health in Dicun River basin is generally in a "healthy" state.The source of Dicun River Stream(YT),Piliao(PL)and first-class dam(YB)sample plots are "very healthy",but there are still some sections that did not satisfy the standard,such as the second-class power station(ED)and third-class power station(SD)sample plots are "subhealthy",and even the estuary(HK)sample plots appear "unhealthy",so further work needs to be done by protection of environment sectors.