Investigation And Risk Analysis Of Alien Invasive Plants In Urban Green Space System In Nanning

In order to fully understand the current situation and possible risks of alien invasive plants in the urban green space system of Nanning,and to do a good job of prevention and control,this paper investigates and analyzes the status and risks of alien invasive plants in the urban green space system of Nanning.The main research results are as follows:1.According to the conditions of different urban areas and different types of green space,the author randomly selected some green space units in the urban green space system of Nanning to investigate the current situation of alien invasive plants,and finally selected 34 green space units.The comprehensive investigation method or line investigation method was used to investigate the status of alien invasive plants in the selected 34 green space units,and the main conclusions are as follows:(1)There are 116 alien invasive plants in Nanning urban green space system,belonging to 32 families and 88 genera.Among them,there are 104 dicotyledons belong to 76 genera and 28 families,12 monocotyledons belonging to 11 genera and 4 families.Among the dicotyledons,Compositae,Leguminosae,Euphorbiaceae,Amaranthaceae,and Solanaceae are the main species,and among the monocotyledonous,Gramineae is the main species.(2)According to the statistical analysis of the distribution of alien invasive plants,in the urban green space system of Nanning,there are 11 alien invasive plants,which belong to 5 families and 9 genera,distributed in more than 30 green space units;there are 22 alien invasive plants,belonging to 10 families and 18 genera,distributed in(20,30]green space units;and 37 alien invasive plants,belonging to 14 families and 32 genera,distributed in(10,20]green space units;46 alien invasive plants,which belong to 23 families and 38 genera,distributed in less than 10 green space units.(3)According to the statistical analysis of life style,there are 96 species of herbaceous plants in the alien invasive plants of the urban green space system in Nanning,which belong to 29 families and 76 genera.Included 54 species of annual herb belonging to 15 families and 39 genera;2 species Biennial herb belonging to 1 family and 2 genera;33 perennial herbaceous plants belonging to 19 families and 30 genera;7 grassy vines belonging to 4 families and 6 genera.There are 7 species of trees,which belong to 5 families and 6 genera.Included 5 evergreen trees belonging to 4 families and 4 genera;2 deciduous trees belonging to 2 families and 2 genera.There are 13 species of shrubs,which belong to 6 families and 10 genera.Included 10 species of evergreen shrubs belonging to 5 families and 8 genera;3 species of deciduous shrubs belonging to 3 families and 3 genera.(4)According to the statistical analysis of the origin of the species,there are 89 species of alien invasive plants native to the Americas in the urban green space system of Nanning,belonging to 28 families and 67 genera;10 species of alien invasive plants native to the Africa,belonging to 6 families 8 Genus;7 species of alien invasive plants native to Asia(except China),belonging to 4 families and 7 genera;5 species of alien invasive plants native to Europe,belonging to 5 families and 5 genera;2 species of alien invasive plants native to Oceania,belonging to 2 families and 2 genera;However,there are 3 species of alien invasive plants of unknown origin,belonging to 3 families and 3 genera.2.On the basis of investigating the current situation of alien invasive plants in the urban green space system of Nanning,the authors uses the multi-index comprehensive evaluation method,expert survey method,analytic hierarchy process,particle swarm optimization algorithm,hierarchical total ranking and expert group decision making method,basing on factors that cause risks from alien invasive plants,to construct risk assessment system for alien invasive plants in urban green space system of Nanning,then evaluate the alien invasive plants of the urban green space system in Nanning.The main conclusions are as follows:(1)The evaluation system is divided into three levels:target level,criteria level and indicators level.It consists of 1 target,4 criteria and 15 indicators.(2)The alien invasive plants with a score of>50 were defined as the first-level risk plants,the alien invasive plants with a score of(30,50]were defined as the second-level risk plants,and the alien invasive plants with a score of<30 were defined as the third-level risk plants,and there were 37 first-class risk plants belonging to 16 families and 34 genera in Nanning urban green space system;77 second-class risk plants belonging to 34 families and 64 genera;and 2 third-class risk plants belonged to 2 families and 2 genera.3.The paper discusses the similar investigation and evaluation system in China,and puts forward the innovation and insufficiency of the research methods of this survey.Finally,it puts forward the preliminary suggestions on the prevention and control of alien invasive plants in the urban green space system of Nanning.(1)Conducting research on alien invasive plants in the urban green space system of Nanning.(2)The quarantine of imported plants in Nanning should be strengthened.(3)The prevention and control measures for alien invasive plants in the urban green space system of Nanning should be strengthened.(4)Reduce the introduction of garden plants and increase the use of native tree species.