Effects Of Clonal Integration On The Growth And Competition Of Alternanthera Philoxeroides And Its Related Species Under Fluctuating Environment

Invasive plants have affected the stability of the ecological environment and species diversity globally,and their influence has gradually expanded from ecology to economic and political fields.As a model plant in the study of invasive clonal plants,Alternanthera philoxeroides has a strong ability of resource integration,growth,and reproduction due to its unique clonal life history,which may break through the time and space limitations of resources and environment,and achieve successful invasion of various types of ecosystems.In recent years,global change has increased the frequency and degree of disturbance to global or regional ecosystems and increased the degree of dispersion of environmental elements in habitats.Existing studies focus on spatial heterogeneity of environmental factors but lack attention on periodic or aperiodic changes caused by disturbances.Since space and time are inseparable in nature,it is necessary to consider the two factors when analyzing the heterogeneity of habitat resources.In this paper,an invasive plant named Alternanthera philoxeroides was selected as the main research object,and a non-invasive alien species named Alternanthera bettzickiana and a native species named Alternanthera sessilis were selected as the comparison to study the effects of resource and environmental fluctuations on the growth and physiological performance of Alternanthera philoxeroides and its relatives,as well as the role of physiological integration in the interspecific competition process.In order to further reveal the mechanism of clonal integration in the successful invasion of Alternanthera philoxeroides.The main research results of this paper are as follows:(1)In this study,an interspecific competition experiment was designed to compare the competition between exotic species of Alternanthera philoxylum and Amaranthus grandiflorum,which were both exotic species.At the same time,in the competitive environment,the patch fluctuation of water resources caused by precipitation and hydrology changes may be simulated in the natural environment.In this experiment,two resource levels were set at the tip of the tested plants.One was an equilibrium environment in which water was added uniformly over time.The growth of the two plants was observed under general spatial heterogeneity.The other is a fluctuating environment in which water is added in a non-uniform way over time,to observe the effects of fluctuating and heterogeneous conditions on the growth and reproduction of the two plants and the role of clonal integration in it.The results show that the fluctuation of resources and environment can affect plant growth,and different plants have different responses to the fluctuation of resources and environment.Different from the expectation,the growth and physiological performance of the invasive species were improved in the water fluctuating environment.Water fluctuation reduced the growth performance of plant apex only when there was no connection between ramets and competition.In contrast,the fluctuation of resources had a certain degree of negative effect on the growth of Alternanthera bettzickiana.Furthermore,in the fluctuating resource environment,the degree of interspecific competition between the two plants was different: the fluctuating water resource environment did not affect the Alternanthera philoxeroides,but reduced the competitiveness of Alternanthera philoxeroides.To a certain extent,clonal integration improved the competitiveness of Alternanthera philoxeroides and Alternanthera philoxeroides under the condition of resource balance,and had a mitigating effect on the negative effects of environmental fluctuation,but this effect may be more reflected in the reproductive strategy of plants than directly reflected in the growth performance or competitiveness of plants.(2)In this study,we selected the invasive species Alternanthera philoxeroides and the native species Alternanthera sessilis,designed the competition experiment between the alien species and the native species,and directly compared the competitiveness of the two species,and simulated the fluctuation disturbance and stress that might occur in the natural environment in the competitive environment.To salt stress factor for the stress in the experiments,the group set up without stress to blank contrast,in the apex of plant set up two kinds of stress level,the soil salt content increases at a constant speed over time the balance of the change of environment,second,the soil salt content increased volatility over time environment,observe the heterogeneity of stress equilibrium and fluctuations in the influence of two kinds of plant competition,And the role of clonal integration in this.The results showed that the biomass,physiological index and clonal growth index of xerophilous lotus seed grass and native lotus seed grass were significantly affected by the fluctuating increasing salt stress environment.The increase of salt stress fluctuation had a greater inhibition effect on the native Alternanthera sessilis.In contrast,the Alternanthera philoxeroides seaweed showed more robust adaptability under the disturbance of non-nutritive resources.Salt stress did not intensify interspecific competition,but the intensity of interspecific competition decreased in salt stress.Clonal integration in salt stress has no direct impact on competition,stolons shear and the connection has not changed the competition results,but the cloning of integrated plant in a certain extent,the structure and function of specialization,through the different growth strategy and the strategy to realize the effective use of resources and adaptability to bad environment to survive.Summary: The growth of Alternanthera philoxeroides and its related species responded differently to the fluctuation of resources and environment,and Alternanthera philoxeroides showed stronger adaptability to disturbed habitats.Environmental changes significantly affected the interspecific competition of Alternanthera philoxeroides and its related species,and the competition of native species decreased more obviously.In the presence of clonal integration,the structure and function of the plant were more specialized,and different growth and reproduction strategies were used to achieve effective utilization of resources and adaptive survival to harsh environment.