Growth Responses Of Festuca Elata Keng And Agrostis Matsumurae Hack To The Invasion Of Alternanthera Philoxeroides In Different Urban Habitats

Under the influence of the accelerating urbanization process,the change and comprehensive interaction of urban environmental factors will produce multi-dimensional and complex interaction,resulting in the difference of urban habitats.It will also affect the growth of plants growing in urban habitats,resulting in fluctuations in morphology,physiology and biochemistry.Lawn,as an important part of urban greening,also faces the difficulty of exotic weed invasion.In this study,two kinds of turfgrass,Festuca elata Keng,Agrostis matsumurae Hack and invasive weed Alternanthera philoxeroides,were used as materials,and the zero hardening habitat(S1),semi-hardening habitat(S2),total hardening habitat(S3)within a diameter of 20 m were used to simulate the change of habitat during urbanization.The main findings of the study are as follows:(1)In the process of urbanization,different habitats had different effects on the morphology,physiology and biomass of Festuca elata Keng,Agrostis matsumurae Hack,and Alternanthera philoxeroides.From S1,S2 to S3,the plant height,Internode length,leaf relative water content and chlorophyll content of the three herbs showed a decreasing trend in different ranges.And its superoxide dismutase(SOD),peroxidase(POD),catalase(CAT),ascorbate peroxidase(APX)content and soluble protein(SP),soluble sugar(SS),The contents of free proline(Pro)and malondialdehyde(MDA)were also determined.The above-ground biomass,total biomass and root-shoot ratio also showed a decreasing trend,while the underground biomass showed an upward trend,but there was no significant difference between the above-ground biomass and the total biomass,total biomass and root-shoot ratio.Root activity and average root diameter decreased,total root length,total root surface area,total root volume,fractal dimension,root tip number and branch number increased significantly,but there was no significant difference in connection number.(2)The invasion of Alternanthera philoxeroides had different effects on the growth of Festuca elata Keng and Agrostis matsumurae Hack.Under the influence of weed invasion,the plant height,Internode length,leaf relative water content and chlorophyll content of the two species of turfgrass decreased compared with the control under the three habitats.The above-ground biomass and total biomass also showed a downward trend,while the underground biomass had no significant change,the root-shoot ratio increased,antioxidant enzyme SOD,POD,CAT,APX and osmotic regulators SP,SS,Pro and MDA increased significantly.Root activity and average root diameter decreased,total root length,total root surface area,total root body The increase of product,the fractal dimension,the number of root tips,the number of branches are also on the rise,and the number of connections is not significant.(3)The invasion of mixed lawn could significantly reduce the plant height,Internode length,leaf relative water content and chlorophyll content of Festuca elata Keng and Agrostis matsumurae Hack,in mixed sowing,but the extent of decrease was lower than that of monoculture.The total root length,total root surface area,total root volume,fractal dimension,root tip number and branch number of the two kinds of turfgrass in mixed sowing increased significantly when invaded by weeds,and the extent of increase was larger than that of unicast invasion.The root activity showed a downward trend,which was smaller than that of unicast under the influence of invasion,and the average root diameter decreased,which was larger than that of unicast invasion.There was no significant difference in the number of connections.The activities of several enzymes are as follows: osmotic substances also increased to varying degrees,but the proportion of increase was smaller than that of unicast when it was invaded.The above ground biomass and total biomass showed a downward trend,which was smaller than that when unicast was invaded,the underground biomass had no significant change,the root-shoot ratio increased,and the increase range was larger than that when unicast was invaded.On the whole,different habitats of urbanization process had different effects on the growth of three species of plants.The higher the degree of urbanization,the greater the degree of plant growth was affected.The effects of habitat change on different plants also showed that the ability of different plants to adapt to the complex environment of urbanization was different,and the growth of two kinds of turfgrass increased with the increase of urbanization degree,and the growth of two kinds of turfgrasses increased with the increase of the degree of urbanization.The ability of mixed-sowing turf to resist the invasion of exotic weeds was higher than that of single-sowing lawn.Therefore,in the case of irreversible urbanization,to strengthen the management of urban turfgrass,it is necessary to choose more resistant turf grass varieties as far as possible,and more varieties are needed to improve the management of urban turfgrass.The mixture of turfgrass and grass could enhance the diversity and stability of the community and effectively inhibit weed invasion.