Effect And Mechanism Of Tamarix Shrub On Surrounding Soil Salinity In The Yellow River Delta

With its unique physiological and ecological characteristics,Tamarix grow in saline alkali habitat and play an important role in the improvement of saline soil.In order to explore the impact of Tamarix on the ecological environment of saline alkali land and its action mechanism on soil salt,this paper takes Tamarix in the wetland of the Yellow River Delta and surrounding soil as the research object,analyzes the salt differences of Tamarix roots,stems,leaves and surrounding soil by means of analysis of variance and factor analysis,and reveals the impact of Tamarix on soil salt and its action mechanism.The results show that:（1）The level of soil salt content is not only related to the depth of soil layer,but also related to the distance and orientation from Tamarix.The contents of Cl^-,Na⁺,Mg²⁺,Ca²⁺,EC and TS in the topsoil decreased with the closer to the center of Tamarix,and K⁺,SO₄^2-also decreased in the topsoil in the east of Tamarix.Among them,the surface aggregation of Cl^-,Na⁺,Mg²⁺,Ca²⁺,EC and TS in the east and west of Tamarix gradually weakens with the closer to the center of Tamarix.On the south side of Tamarix,the above indicators have no obvious surface aggregation characteristics at 0.5m away from Tamarix,but the surface aggregation phenomenon is more significant at 1m away.There were significant differences in salt ion surface aggregation in different directions of Tamarix.K⁺showed apparent aggregation in the east,south and west of Tamarix;SO₄^2-shows apparent aggregation in the oriental position;HCO₃^-increased first and then decreased with the increase of soil depth in the east,south and west of Tamarix.Multivariate analysis of variance showed that depth,distance and direction had significant effects on most salt indexes in soil.（2）The effect of Tamarix on soil salt is the most significant in the range of 0.5m around it.In the 0～10cm soil layer,the variation coefficients of Cl^-,Na⁺,Mg²⁺,Ca²⁺,EC and TS in the east,south and west of this range are large.Compared with the salt 2m away from Tamarix,the decline range of the above salt ions in this range is higher than 50%,and the decline range in the east is even higher than 60%,forming an obvious"Salt Valley".At1m,the decrease range of the above salt ions is mostly less than 40%,which roughly shows the characteristics that the farther the distance is,the smaller the decrease range of salt content is.There are differences in the decline of different salt ions in space.The difference in the decline of Na⁺,Ca²⁺,Mg²⁺has an impact on the spatial distribution of SAR,so that its change characteristics horizontal directions indifferent directions are not uniform.（3）The results of factor analysis showed that the dominant factors of salinity in Tamarix and the surrounding soil were the same,mainly Cl^-,Na⁺,Mg²⁺.From the perspective of the selectivity of Tamarix for salt ions,the selective absorption coefficient of cations is K⁺>Ca²⁺>Mg²⁺,and the anion is SO₄^2-greater than HCO₃^-,so the salt content in Tamarix is SO₄^2->Na⁺>Ca²⁺>K⁺>Mg²⁺>Cl^->HCO₃^-.The content of Na⁺in soil cations is high,so that the content of Na⁺in Tamarix remains high;The content of K⁺is the lowest,and its content in plants is lower than that of Ca²⁺.From the perspective of selective transport coefficient,the root of Tamarix has strong transport capacity for K⁺,the branch has strong transport capacity for Ca²⁺,Mg²⁺,SO₄^2-,and the salt content in litter is the highest,followed by leaves,branches,stems and roots.