Effects Of Human Disturbance On Plant Diversity In Yangshan Wetland

Wetland plants are an important part of wetland ecosystem and play an important role in maintaining the stability of the ecosystem.In this study,the vascular plants in Yangshan Wetland were investigated and counted in different phenology and seasons,and the background data of plant resources in Yangshan Wetland were obtained.At the same time,artificial disturbance zones of Yangshan wetland were divided by 3S technology,and 220 samples were set up in different disturbance zones.Based on comprehensive investigation,plant diversity indices of different disturbance zones were compared and analyzed.The effects of human disturbance on plant diversity of wetland were studied,and phytoremediation allocation modes of different site conditions were recommended.The results were as follows:(1)There are abundant plant resources in Yangshan wetland.According to investigation and statistics,758 species of vascular plants are recorded,belonging to 119 families and 413 genera.Among them,25 species of pteridophytes belong to 14 families and 18 genera;2 species of gymnosperms belong to 1 family and 1 genera;660 species of angiosperms belong to 104 families and 394 genera.(2)Gramineae,Euphorbiaceae and Compositae are the most abundant vascular plants in Yangshan wetland.The other families with more species are Rubiaceae,Acanthaceae,Araceae,Cyperaceae and so on.Common genera are Ficus,Cyperus,Polygonum,Syzygium and Mallotus,among which Cyperus and Polygonum are very common and important genera in tropical secondary grasslands.(3)The ecological environment of Yangshan wetland is better as a whole,the vegetation condition is generally good,the degree of human disturbance is low,and the area of weak disturbance is the largest,reaching 195.33 km2,accounting for 52.57%of the total area.Comparing the dynamic changes of Yangshan wetland disturbance area in 2009 and 2017,it is found that the area of weak disturbance area decreases and the area of severe disturbance area increases due to the acceleration of urbanization,the occupancy of construction projects and intensive land development.With the intensification of man-made interference,the weak interference area gradually transforms to light interference and heavy interference,and the light interference area increases greatly.(4)Among the arbor plants distributed in Yangshan Wetland,azedarach was the most frequent,followed by Ficus quinquefolia,Ginger and Thickbark.The shrub layer is less distributed,the species is single,and the highest frequency is Mudan,which is much larger than the wine cake.The high frequency of Bidens bipinnata,a herbal plant,once again proves its invasion tendency in Yangshan wetland.Subsequent concentrated herbs such as flying grass,mimosa,Ricinus communis,South American Python chrysanthemum,silver gum chrysanthemum and so on belong to invasive species.It can be seen that in the plant community of Yangshan wetland,the invasive situation of herbaceous layer plants is severe.From the total frequency of plants,the top 10 herbaceous species accounted for 46.91%of the total frequency.The sum of the top ten plant frequencies in tree,shrub and herb frequency ranking is nearly half of the total frequencies of all kinds of plants,which indicates that the top ten plants in Yangshan wetland with different disturbance degree have higher dominance and higher recorded probability,but the overall uniformity is lower.(5)The plant diversity of Yangshan wetland decreased with the intensification of human disturbance.Tree layer is very vulnerable to human disturbance,and the recovery rate is slow,self-repair ability is weak;shrub layer species are relatively single,the total frequency is low,the recovery ability is weak;herbaceous layer species are relatively rich,and easy to be restored after disturbance,but also easy to bring invasion of alien species.(6)The species number and plant diversity index of Yangshan wetland have a high level.With the increase of disturbance degree,Shannon-Wiener index and Simpson index show a decreasing trend,Pielou index decreases accordingly.Human disturbance has certain screening ability for plant species,strong reproductive ability and strong habitat adaptability.Species can occupy an important position in different disturbance areas.Therefore,in plant protection and wetland restoration,emphasis should be placed on the protection and application of species that are susceptible to interference and are not easy to grow and spread.When restoring wetlands,we should first consider the use of native plants,restore the "near-natural" plant communities,improve plant diversity and community stability,and restore the original ecological functions of plant communities.