Study On The Breeding Strategy Of C. Lobularis Population In The Heterogeneous Habitat Of Wetland In The Sanjiang Plain

With the dual disturbance of natural factors such as temperature and rainfall and human factors such as agricultural reclamation and ditches,the wetland habitat heterogeneity in Sanjiang Plain becomes more and more obvious.This heterogeneity affects a variety of ecological processes and phenomena,and makes plants form adaptive strategies in the process of evolution to cope with the selection pressure of habitat heterogeneity.Plants adopt different strategies in different environments to maximize population expansion.Understanding plant reproduction strategies in heterogeneous habitats is an important measure to explain plant ecological adaptability and manage ecosystems.Taking Deyeuxia angustifolia,the dominant species of wetland in Sanjiang Plain,as the research object,We selected four habitats,including hybrid grass meadow,typical meadow,bog meadow and marsh,to form the heterogeneous habitat series,studied the quantitative characteristics of sexual reproduction and vegetative reproduction of D.angustifolia,discussed the relationship between sexual reproduction and vegetative reproduction,and the response of reproductive characteristics to environmental factors of heterogeneous habitats,in order to explain the reproductive tradeoff strategy of D.angustifolia population to environmental changes,and provide scientific basis for the protection,restoration and management of degraded wetlands in the future.The study found that:(1)There were significant differences in the size,height and sexual reproduction characteristics of D.angustifolia population in heterogeneous habitats,and most of the characteristics showed that the hybrid meadow was larger than the typical meadow and the marsh meadow was larger than the marsh.and the reproductive thresholds of D.angustifolia in miscellaneous grass meadow,typical meadow,swamp meadow and swampy were 0.245,0.149,0.148 and 0.157,respectively.Except for swamp meadow,the individual size of D.angustifolia was negatively correlated with reproductive allocation in the other three habitats.Compared with individual size,habitat heterogeneity had a greater impact on sexual reproduction allocation,the difference of investment in individual size and reproductive distribution in different habitats is the basic condition for good ecological influence of D.angustifolia population.(2)In the process from optimum marsh meadow to typical meadow to hybrid meadow,or marsh meadow to marsh,The proportion of root,stem and bud of D.angustifolia increased,the number of root,stem and bud per plant increased,and the proportion of bud of tiller node decreased,and they all showed significant levels.There was a significant positive correlation between rhizome bud number,rhizome biomass and rhizome length.The rhizome strength of four habitats were MG-0.0050,TM-0.0020,SM-0.0011 and SW-0.0018,respectively.(3)The density,biomass per unit area and aboveground mass fraction of D.angustifolia population in swamp meadow were significantly higher than those in other habitats,so it was the most suitable habitat for D.angustifolia population.The distribution of sexual reproduction of D.angustifolia population was significantly positively correlated with rhizome biomass per plant,and negatively correlated with the number of tiller nodes.Miscellaneous meadows and typical meadows had more investment in sexual reproduction and rhizome lengthening.It tended to be a "coercion-interference" adaptation strategy,while the investment of leaflet was more for vegetative growth and tiller bud ramet in bog meadow and tended to "competitive" adaptation strategy.D.angustifolia resisted the flooded environment by maintaining the balance of resources in the body and tended to the "coercion-endurance" adaptation strategy,which accorded with the CSR theory.Environmental factors explained 74.63% of the variation of reproductive characteristics of D.angustifolia population,in which the explanatory proportion of soil water content,soluble organic carbon,ammonium nitrogen and nitrate nitrogen reached a very significant level,nitrate nitrogen promoted the length of rhizome.Amine nitrogen promoted the biomass of sexual plants,while soil water content inhibited the biomass of sexual plants,soluble organic carbon significantly increased the population density.In the stressed environment,D.angustifolia population produced the escape mechanism by increasing the investment of rhizome and sexual reproduction,while in the suitable habitat,it increased the tiller node bud to produce new plants to expand the population,which was the basis for the leaflet canula to adapt to a larger water gradient.