Study On The Desalination Zone And Its Relationship With Vegetation In The Lower Reaches Of Tarim River

Under the effect of lateral seepage of river in the desert,a certain area of arid inland river in the flood season respond to the effect.In the action of the groundwater lifting and the groundwater salinity advancing farther into riverside,it form the desalination zone with moderating of groundwater depth,soil moisture,groundwater quality,salinity.The desalination zone along river in the desert provides habitat for growth and reproduction to arid area organisms.Based on the field monitoring data,combining vegetation and soil data,using the surface analysis combined with the typical analysis,time series method,the paper discussed the characteristics of the desalination zone;analyzing the characteristics of environment and vegetation spatial-temporal pattern in the desalination zone,illustrating the interaction between the desalination zone and plants.The results showed that:(1)The formation and response rule in the desalination zone along river.Under the effect of the Bosten lake,the total dissolved solid in the 450 m from the river of the Yingsu section was low.Because of the 750 m from the river in the Yingsu section accepted water soluble salt,the total dissolved solid increased.Then,Yingsu section formed the desalination zone with 750 m,Kaerdayi section formed the desalination zone with 850 m.The formation of the desalination zone along the river was a gradual process,and had a certain regularity.By moving water solubled salt,the place that the moving water arrived had the high total dissolved solid.With water delivery continuing,salinity declined while the values with boundary wound not fall.In the Yingsu section,the desalination zone formed in the fifth eological water transfer.(2)The characteristics of water and soil in the desalination zone along river.In the Yingsu section,with the effect of eological water transfer,groundwater depth was 3.39 m,5.10 m,5.11 m,5.17 m in the 50 m,250m,350 m,450m along the river in the desalination zone;After the ecological water interrupted,the changes of groundwater depth in the 50 m,250m,350 m,450m along the river were 5.21 m,5.91 m,6.27 m,6.13 m.The change of groundwater depth in the 50 m from the river was the largest.Out of the desalination zone,groundwater depth were 5.61 m,6.26 m in the 750 m,1050m along the river;After the ecological water interrupted,groundwater depth were 6.74 m,6.72 m,the change of groundwater depth in the 1050 m from the river was the least.Under the dilution of water,the values in the desalination zone were obviously less than those out of the desalination zone.The salinity of the outer zone was 11.4 times of the average value of the desalination zone.The salinity of the desalination zone was the largest,and it was more than that of the out of desalination zone under the effect of extreme drought climate with less rainfall.The soil nutrient in the desalination zone was higher than the out of desalination zone influencing by vegetation residues and root decomposition.(3)The distribution of vegetation in the desalination zone along river.In the terms of difference in the community structure: Taking Yingsu section as an example.In the desalination zone,there were 7 kinds of plants belonging to 5 families and 6 genera.In the vertical direction,there were tree layer,shrub layer and herb layer from top to bottom.The mosaic distribution in the horizontal direction,community type was Populus euphratica –Tamarix–Alhagi sparsifolia.Out of the desalination zone,there was no trees and herbaceous plants.The vertical and horizontal structure were a single community for Tamarix.In the terms of species diversity,there were high diversity with low richness community characteristics in the desalination zone.Out of the desalination zone,the species diversity and richness were low and the degree of uniformity was high.(4)Relationship between vegetation and the desalination zone along river.The relationship between habitat and plant types: according to the difference of salt water,environment was divided into suitable zone,low grounewater level-medium salinity zone,low groundwater level-high salinity zone.According to the difference of vegetation index,it was divided into few species-high coverage zone,multi species-low coverage zone and few species-low coverage zone.According to the relationship between vegetation and environment,the species was divided into high groundwater level-medium salt mesophyte,low groundwater level-medium salt mesophyte and low groundwater level-halophilous mesophyte.Time series analysis,the groundwater depth reduced year by year in and out of the desalination zone along river but the trend was not significant(P>0.05);the total dissolved solid out of the desalination zone significantly decreased in the two curve model of y =-0.0035x2-0.7866x+23.959(R2=0.8956,P<0.01).Vegetation cover were significant linear growth trend with y=5.13x-1.6787(R2=0.5471,P<0.05)out of the desalination zone while trend was not obvious in the desalination zone.Based on resource utilization,and human disturbance,the species diversity in the desalination zone showed significant linear decreasing trend(P<0.05).Out of the desalination zone,its diversity remained relatively stable level and a linear decreasing trend was not significant(P>0.05).