Effects Of Root Cutting On Population Dynamics And Reproductive Strategies Of Leymus Chinensis

The study aims to determine the reproductive strategies and life strategies of Leymus chinensis population in their adapting to adversity,and to explore the methods of root-cutting improvement of mildly and moderately degraded L.chinensis grassland.In the study,root-cutting treatments with spacing of 10 cm,20 cm and 30 cm were carried out during the vegetative growth period of L.chinensis(prophase,metaphase and anaphase),respectively so as to study the effects of root cutting on population dynamics of L.chinensis,leaf,stem,spike,rhizome biomass,nutrient element content(total N,total P),energy accumulation resource allocation and reproductive allocation.By comparing and analyzing the sexual and asexual reproduction of L.chinensis,this paper clarifies the evolution law of population characteristics,grassland community,resource allocation and reproductive strategy of degraded L.chinensis after root-cutting improvement,thus providing theoretical basis for the scientific management of L.chinensis grassland.After continuous observation and sampling of L.chinensis population throughout the growing season,the research results are as follows:The height,density and aboveground biomass of L.chinensis population were reduced to varying degrees by cutting roots on slightly degraded L.chinensis grassland in the same year.In moderately degraded L.chinensis grassland,the height of L.chinensis population was increased by cutting roots 30 cm before vegetative growth,the density of population and aboveground biomass were increased by cutting roots 30 cm during vegetative growth,and the height and density of population were decreased by cutting roots 10 cm before vegetative growth.In the same period,the height and density of the cut-root L.chinensis population showed spacing of 10 cm < 20 cm < 30 cm.In the slightly degraded L.chinensis grassland,the reproductive distribution of L.chinensis could be improved by the root cutting spacing of 30 cm at late vegetative growth,while the resource distribution of L.chinensis could be improved and the total nitrogen distribution of rhizome could be decreased by root cutting spacing of 30 cm at prophase of vegetative growth respectively;In moderately degraded L.chinensis grasslands,the reproductive distribution of L.chinensis could be improved by the root cutting spacing of 30 cm at prophase of vegetative growth,and root cutting spacing of 30 cm at middle trophic growth could improve the total nitrogen distribution of leaves and reduce the total nitrogen distribution of roots;In two different kinds of degraded L.chinensis grasslands,the root cutting spacing of 10 cm at prophase of vegetative growth can increase the biomass and energy distribution of rhizome,thus reducing the biomass and energy distribution of aboveground components,and promoting the rejuvenation and renewal of rhizome.When the root-cutting distance was 10 cm,the resource transportation of rhizomes was severely restricted,the germination rates of rhizome buds and tillering node buds increased with the increase of the resource allocation proportion of rhizome,and the sexual reproduction was relatively poor,which inhibited sexual reproduction of L.chinensis and promoted asexual reproduction of L.chinensis.When the root-cutting distance was 30 cm,sexual reproduction and asexual reproduction of L.chinensis coexisted,which was more conducive to sexual reproduction of L.chinensis.