Spatial Pattern And Influencing Factors Of Clonal Plant Phragmites Australis Population In Yangguan Wetland Of Dunhuang

Plant spatial pattern is the result of long-term interaction of multiple mechanisms in plant ecosystem,which is closely related to the ecological process of species and can represent the dynamic development process of population.As a unique natural resource,wetlands have severely declined in recent years and the ecological environment has gradually deteriorated.In particular,wetlands in the Chinese northwest arid regions are both sensitive and fragile.As the dominant species in wetlands in arid regions,Phragmites australis adopts clonal reproduction to replenish and renew.It has strong ecological adaptability and plays a vital role in maintaining the stability of the wetland ecological environment in arid regions.This paper takes the clonal plant Phragmites australis in the Yangguan wetland of Dunhuang as the research object.Three different sampling gradients are set up in the high coverage area,medium coverage area and low coverage area,and the pair correlation function of g(t)was applied.Analytical method,redundancy analysis,and multiple linear regression model have studied the spatial pattern of Phragmites australis population and the relationship between its influencing factors.The aim is to clarify the formation mechanism of the Phragmites australis spatial pattern and its adaptability to the environment from the perspective of the spatial pattern,in order to further clarify the ecological adaptation countermeasures of the cloned plant Phragmites australis in the arid area wetland,and to protect the sensitive and fragile inland river wetland ecosystem Provide theoretical basis.The main findings are as follows:(1)In the study area,the Phragmites australis population coverage was automatically divided into high coverage(65.53-96.23%),medium coverage(34.77-65.53%)and low coverage(4.01-34.77%)using ArcGIS.With the decrease of the coverage,the average soil water content and soil pH showed a gradual downward trend,and the soil salinity showed a significant upward trend(p<0.05);the soil under the three gradients of high,medium and low coverage The water content showed an increasing trend from the surface to the deep layer(p<0.05),and the soil salt content showed a decreasing trend from the surface to the deep layer(p<0.05).(2)The density,frequency,height and above-ground biomass of the population characteristics of Phragmites australis from high coverage to low coverage showed a decreasing trend;the characteristics of clonal components gradually changed from high coverage to low coverage with stem thickness,number of nodes,and number of leaves decrease(p<0.05),while the rhizome internode length,spacer length and branch angle gradually increased(p<0.05).Physiological characteristics showed that the content of starch and NSC in the whole plant of Phragmites australis gradually decreased,and the content of soluble sugar showed a trend of first increasing and then decreasing;the starch content of leaves,stems and rhizomes among the various components appeared in the high coverage area.High value,while the starch content of the root presents a high value in the low coverage area;the soluble sugar content is shown as the stem and rhizome gradually increase during the transition from the high coverage area to the low coverage area,while the leaves and roots gradually increase decreasing characteristics;NSC content is characterized by the gradual decline of leaves and stems,the rise of rhizomes first and then decline,and the gradual rise of root components.(3)In the spatial pattern of Phragmites australis under high coverage,the spatial distribution form is dominated by aggregation and the aggregation intensity is high.The patch differentiation is characterized by small plaque area,large territory area and high territory density;under medium coverage,the scale of aggregation distribution is reduced and The aggregation intensity is reduced,and the characteristics of patch differentiation show that the area of plaques is increased,the area of territory is reduced,and the density of territory is reduced;the spatial distribution pattern tends to be completely random under low coverage,the aggregation intensity is the smallest,and fewer surviving plants lead to patch differentiation.It is characterized by a significant increase in the area of plaques and a significant decrease in the area and density of the territory.(4)The analysis of the factors affecting the spatial pattern of Phragmites australis concluded that the average soil water content and soil salt content are important environmental factors affecting the spatial pattern.At the same time,the soil water content and soil salt content of each layer and the surface pH value have significant effects on the space;component characteristics The rhizome internode length and spacer length can affect the aggregation strength of Phragmites australis;the density of population characteristics also has a greater impact on the spatial pattern of Phragmites australis.The effect of leaf and root starch content in non-structural carbohydrates on aggregation strength also reached significant.