| Plant functional traits are a series of plant attributes that significantly affect plant colonization,survival,growth and death,and can reflect the ability of plants adapt to the external environment.The trade-off between functional traits reflects the different strategies adopted by plants in resource acquisition and allocation as well as the evolution and balance among the functions of various organs.Inland salt marsh wetland is a kind of wetland ecosystem with a special ecohydrological process and highly heterogeneous environment.Leymus secalinus is a perennial rhizome grass widely distributed in inland salt marsh wetlands,the study on the relationship between resource allocation and functional trait trade-off of L.secalinus is helpful to understand the unique adaptation mechanism of salt marsh plants,it is of great significance to reveal the life history strategies of wetland plants.Because of this,60 sample sites were set up in the Yanchiwan internationally important wetland,perpendicular to the direction of the Danghe River.(plot I: soil moisture content 22.3%-24.6%;plot II: soil moisture content 16.8%-18.2%;plot III: soil moisture content 12.6%-14.5%;plot IV: soil moisture content 7.3%-9.6%),one-way ANOVA,correlation analysis,trade-off value,and structural equation model were used.The biomass allocation model of L.secalinus under different water gradients was analyzed,the tradeoff relationship between functional traits of L.secalinus was studied,and the habitat adaptation characteristics of L.secalinus were discussed,which provided a theoretical basis for vegetation restoration of the international important wetland in Yanchiwan.The results showed that:(1)With the decrease of soil water content,the coverage and density of the wetland community decreased gradually,and the community height increased and then decreased in an inverted "V" type trend.The height and density of L.secalinus population increased first and then decreased,and the population coverage showed a complex trend of decreasing,then increasing,and then decreasing with the decrease of soil water content.There were significant differences in biomass allocation among different species(P <0.05).With the decrease of soil water content,the root-shoot ratio and root-mass ratio of L.secalinus increased gradually,the flower mass ratio decreased and then increased,the stem mass ratio decreased,then increased and then decreased,and the leaf mass ratio decreased gradually;The ratio of flower biomass to plant area increased after decreasing,the ratio of stem biomass to plant area decreased after increasing,but the ratio of leaf biomass to plant area had no significant change(P > 0.05).The lower biomass ratio of the main root biomass allocated to L.secalinus showed a "V" shaped trend of decreasing and then increasing,while the lower biomass ratio of the lateral root biomass allocated to L.secalinus showed an increasing and then decreasing trend.(2)There were significant differences in functional traits among different L.secalinus(P < 0.05).With the decrease of soil water content,leaf thickness,leaf length,leaf number,leaf width and stem length of L.secalinus all increased firstly and then decreased,while stem diameter gradually decreased.Root length,root surface area,root forks and specific root length increased first and then decreased,root diameter decreased and then increased,and root branch angle increased gradually.(3)There were significant differences in the tradeoff of functional traits among different L.secalinus(P < 0.05).The tradeoff between leaf thickness,leaf length,leaf number and stem length in plot I,plot II and plot III was favorable for leaf thickness and leaf number;plot IV was favorable for leaf length and stem length,respectively,the tradeoff between leaf length,stem length,leaf thickness and leaf width in plot I preferred leaf length and leaf thickness,while plot II,plot III and plot IV preferred stem length and leaf width.The trade-off between leaf thickness and leaf number was similar,and the tradeoff tended to be leaf number in various plots.The trade-off between leaf length,stem length,leaf thickness and leaf width in plot I preferred leaf length and leaf thickness,while plot II,plot III and plot IV preferred stem length and leaf width.The trade-off between leaf thickness and leaf number was similar,and the trade-off tended to be leaf number in various plots.Leaf thickness-root forks-leaf width-root surface area and the trade-off between stem length and root length in the sample area to sample I,II and IV preference root traits,sample III preference functional traits on the ground,leaf length,root surface area,leaf thickness,there was a convergence,the trade-off between root length of preference root traits respectively,leaf length-root forks,stem length,root diameter of the trade-off between plot I and II preference root function traits,sample III and IV sample lands preference functional traits or no preference any properties on the ground,leaf number and root traits of complex trade-offs preference.(4)According to the results of structural equation model fitting,measuring the latent variables in the model to the observed variables has good explanation ability.Soil environment directly impact on the community density and height is small,direct impact on the community coverage is larger,the community characteristics of leaf width,leaf length,stem length,stem diameter and leaf thickness of the direct impact is bigger,the soil environment on the stem length and leaf width of indirect impact is bigger,the stem diameter,leaf number,leaf length leaf thickness less indirect effects;Community characteristics had a greater direct effect on root length,root surface area and root branch angle,but a smaller effect on root diameter and root forks.Soil environment had a smaller indirect effect on root length and root branch angle,and a smaller indirect effect on root length and root branch angle.Community characteristics adjust the resource absorption range of L.secalinus root system to adapt to environmental stress,and responds to changes in the soil environment by adjusting its own absorption area.As a bridge connecting plants and the environment,plant functional traits show considerable plasticity in their morphogenesis,survival behavior.The Community environment is an important factor affecting the growth of plant functional traits.Plants choose the construction mode of traits that is beneficial to their survival and reproduction by adjusting their functional traits,which reflects the adaptation of plants to the environment and the special regulation mechanism and survival strategy among different functions in plants. |
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