Composition of vascular plants and the influence of exotic species on floristic characteristics in hilly areas of upper and middle reaches of Yangtze River:a case study of Nanxi of Yibin and Huangpi of Wuhan City
The hilly area of the Yangtze River Basin is a very important and sensitive area for ecosystem service func-tions.The disturbance of human activities leads to the damage of natural habitat and the invasion of alien species.Taking the Nanxi District in Yibin,Sichuan Province and Huangpi District in Wuhan,Hubei Province,which have similar topog-raphy and the same distance from the Yangtze River,as the research areas,the plant resources in the two areas were in-vestigated to explore the composition of the plant flora and the influence of alien species in the hilly areas of the middle and upper reaches of the Yangtze River.The results show that there are 1 205 vascular plants in Nanxi,including 247 exotic species,and 1 076 vascular plants and 150 exotic species in Huangpi.There are more monotypic families and oligotypic families in both places,Asteraceae,Rosaceae,Fabaceae,Poaceae and Lamiaceae are all the five largest families with the highest number of species in two places.The floristic components of both places are mainly cosmopolitan and pantropical plants,followed by temperate plants.The composition of the pantropical flora is larger than that of the northern temper-ate zone,indicating that there is a regional transition from tropical to temperate zone.After the removal of exotic species,there are 364 identical vascular plants in both places,the species similarity coefficient is 24.09%.From the perspective of floristic differentiation intensity,the differentiation degrees of families and genera in the two places are all relatively low,ranging from 1.5 to 3.5,which is consistent with the topography and landfroms of the two places.The exotic species are mainly composed of Compositae,Fabaceae and Solanaceae,with 20.5%of the total species in Nanxi and 13.94%in Huangpi.Although the alien species increase the species diversity in two places,their influence on their floristic composi-tion is not significant.
Yangtze River basinhilly areaflora compositionflora differentiationalien plant