Spatial Distribution And Influencing Factors Of Plant Communities In The Lower Reaches Of The Tarim River

The natural plant communities in the lower reaches of the term river were studied.By using quantitative ecology,statistics,geostatistics and other methods,this paper analyzes the quantitative characteristics of plant communities,the spatial distribution characteristics of major environmental factors and the interaction between them,in order to reveal the spatial distribution characteristics of plant communities in downstream regions and the relationship between them and major environmental factors.It provides a theoretical basis for natural plant community restoration and ecosystem protection in the arid region of the lower reaches of trim river.The main results are as follows:(1)The TWINSPAN classification classifies the plant community in the lower reaches of the Tarim River into nine types of plant clusters:Ass.Phragmites australis,Ass.Tamarix ramosissima-Phragmites australis+Halogeton glomeratus,Ass.Alhagi sparsifolia-Apocynum venetun+Hexinia pofydichotoma,Ass.Tamarix ramosissima+Alhagi sparsifolia,Ass.Populus euphratica-Alhagis parsifolia-Phragmites australis,Ass.Populus euphratica-Tamarix ramosissima-Phragmites australis,Ass.Populus euphratica-Tamarix ramosissima,Ass.Tamarix ramosissima+Lycium ruthenicum,Ass.Halimodendron halodendron+Tamarix ramosissima.Within 50 m from the river,there are mainly clusters with dominant species of Phragmites australis herbaceous plants,shrub plant Tamarix ramosissima,and magaphanerophytes Populus euphratica;as the distance from the river increases,shrubs are mainly distributed within the range of 50-150 m The clusters of plant Halimodendron halodendron as the dominant species,as the distance from the river continues to increase,within the range of 150-500 m are mainly distributed herbaceous plants Phragmites australis and Apocynum venetum,shrub plant Alhagi sparsifolia and Tamarix ramosissima and magaphanerophytes Populus euphratica Clusters of dominant species;with the continuous increase of the distance from the river,within the range of 500-1050 m,there are mainly distributions of magaphanerophytes Populus euphratica and shrubs Tamarix ramosissima as dominant species.(2)In the transverse direction along the river,with the increase of the distance from the river,the number of plant species and the concentration of species showed a gradual decrease trend,and the life form of the species was gradually changed from trees,shrubs,herbs to a single shrub or tree plant.In the longitudinal direction along the river,from the Insu-Arakan-Kaogan section,the number of plant species and the concentration of species showed a trend of decreasing first and then increasing.The life form of the species was changed from trees,shrubs,herbs to trees,The shrubs are then transformed into trees,shrubs,and herbs.(3)The ranking results of the 10 environmental factors through DCA,CCA,and DCCA all show that the total salt and groundwater depth have a greater influence.The buried depth of groundwater is gradually increasing from east to west along the river,while along the river,it has the spatial distribution law of "low at both ends and high in the middle" from north to south;Soil salt is gradually increasing from east to west along the river,while along the river,it has the spatial distribution law of "high at both ends and low in the middle" from north to south.(4)When the multiple regression tree uses groundwater depth as an independent variable,all samples fall into three types of plant clusters.The number of species and distribution of samples contained in the clusters within the range of groundwater depth 4.5 m,the average density,The Shannon-Wiener diversity index is high.The average cluster height,average coverage,Simpson diversity index,and Pielou uniformity index are higher in the range of groundwater depth 4.2?4.5 m,and the group is in the range of groundwater depth<4.2 m.The Margalef richness index of the clump is higher;when the multiple regression tree uses soil salt as the independent variable,all samples are also divided into three types of plant clump,and the species and samples contained in the clump are within the range of soil salinity? 8.5 mg/g The distribution number,Simpson diversity index,Shannon-Wiener diversity index,and Margalef richness index are higher,and the cluster density is larger in the range of soil salinity<6.2 mg/g,and the population is in the range of soil salinity 6.2 to 8.5 mg/g.The average cluster height,average coverage,and Pielou uniformity index was higher.