| Based on the investigation of the comprehensive community and the determination of ecological benefits of typical communities in this study, both sides of the Songhua River in Jilin city waterfront green space are analyzed and evaluated from the perspective of waterfront green space landscape floristic composition, community types and structure characteristics, the ecological benefits and the evaluation of air quality suitability. Finally some countermeasures are proposed for optimizing the plant community structure in the waterfront green space. The main conclusions are as follows.(1) In the waterfront green space of Jilin city, there are69families,167genera and261species of vascular plants, including1family,1genera and1species of ferns;4families,8genera and16species of gymnosperms;58families,142genera and225species of dicotyledons;19species,16genera and6families of monocotyledon, respectively. The dominant generas are fagopyrum esculentum, meadow sweet, maple, rose and so on; the proportion of trees, shrubs and herbs is close to1:1:2. The plants include15genus types of the distribution areas of Chinese seed plants, and the plant components of north temperate zone stay in obvious advantages. The native plants account for54.23%and the proportion of the cultivated plant is too higher. The plant zonality and regional features are not distinctive.(2) The waterfront green space in Jilin City has a variety of community types and more complex community structure, being classified into17community types and4vegetation types, mainly consisting of mixed broadleaf-conifer forest and mixed broadleaf forest; high frequency of occurrence trees and shrubs are the weeping willow, red spruce, flowering plum, lilac, etc. The waterfront green species richness of herb layer, tree layer and shrub layer is in decreasing trend and the three diversity indexes for the tree layer, shrub layer and herb layer is also in decreasing trend. The vertical structure of community is divided into three types(including three-layer structure, double-layer structure and single layer structure.)and five models(including "tree+shrub+herb","tree+herb","shrub+herb","tree+shrub","single tree"). The overall growth condition is just so so.(3) The plant community in waterfront green space in Jilin city has better characteristics than CK in terms of humidification and cooling temperature, bacteria inhibition, dust absorption, and air negative ions enhancement. The differences of bacteria content in the air, the TSP content and air negative ions are significant between the vertical structures of green space. And the bacteria content and air negative ions also show significant differences between different canopy densities. The humidifying and cooling effects are better in the communities such as PSPF, SUPF and PPCF; the communities with stronger ability of bacteria inhibition include SUPF, PSPF, PF1and CAPF; the communities with better dust absorption are PSPF, CAPF, PF1and SUPF; the community with higher Air negative ions levels are CAPF, PPCF and PSF. There is a significantly positive correlation (P<0.05) between the humidification effect and the community density and coverage; the cooling effect of plant community are very significantly positive correlated with the density of community (P<0.01); the content of air bacteria is very significantly positive correlated with the density of community (P<0.01), while is significantly negative correlated with the crown width (P<0.05); the correlation between the TSP content of air and the average crown breadth and coverage is significantly negative(P<0.05); the air negative ions levels have very significantly positive correlation with the average diameter at breast height average crown width (P<0.01), but have significantly positive correlation with the average tree height (P<0.05).(4) The fuzzy evaluation is used to assess the suitability of air quality in the various plant communities in waterfront green space and park green space. The air quality in75%of plant community and60%park green space is highly desirable. The air quality suitability is highly appropriate in the park green space of residential area, cultural area, and administrative area. It is moderately suitable in the green land of commercial and industrial park; it is highly appropriate in riverside park, is strainedly appropriate in riverbank park and is moderately suitable in Changyi Park.(5) Starting from increasing species diversity, highlighting the regional characteristics of plant landscape, fully creating the ecological benefit, we put forward the recommended list of plants for the waterfront green space in Jilin city, and construct four functional configuration models of plant communities including the humidifying and cooling type, bacteria inhibition type, dust absorption type, and rich air negative ionic type.The research findings would be taken as the scientific basis for converting the community structure and upgrading the function of waterfront green space in Jilin city and provide the technical support for the sustainable development of economy, society and environment in Jilin City. |
