Spatial Variability Of Soil Characteristics And Its Effects On The Growth Of Phragmites Australis In Keriya Oasis

This paper chose a zonal phragmites australis land, located in western part of Karki Village in Keriya Oasis, as a study area, and arranged 28 sample points, collected the phragmites australis'growth indexes such as coverage , height, crown length, crown width and density, chose three soil layers auch as 0～10cm,10～30cm, 30～50cm to colledt soil samples. On the bases of characteristical data of soil pH value, salt ion contents(Na⁺+K⁺, Mg²⁺, Ca²⁺, CO₃^2-, HCO₃^-, CI-, SO₄^2-), soil moisture, studied the spatial variability of soil characteristics of phragmites australis land by using the descriptive statistical analysis and goestatistical analysis. And then, analysed the relation between soil characteristics in each layer and the growth of phragmites australis by using the correlation analysis, in order to provide a theoretical base to improving of the weak ecosystem of the study area.We can infer from the descriptive statistical analysis that the soil of phragmites australis land were alkaline and strong alkaline soil. Number of alkaline soil increased with the increase of soil depth, but the number of strong alkaline soil decreased. Changes of soil pH value in all layers are small, soil pH value in three layers are very similar. The variation coefficients of soil pH value on these three layers were small, and it disposed weak spatial variability. The salinization degree of phragmites australis land weakened with the increase of soil depth, and changed from saline soil to slight salinized soil and non-salinized soil. Among the salt ion contents in three soil layers, CI- content was the most, Na⁺+K⁺ content was next, and CO₃^2- content was the least one, and their contents decreased with the increase of soil depth. Most salt ions exhibited strong spatial variability or very closes to strong spatial variability except from few salt ions that exhibited medium spatial variability. Changes of soil moisture on three layers of phragmites australis land were all large. Soil moisture on three layers exhibited medium spatial variability. Soil moisture increased with the increase of soil depth, but the degree of its spatial variability decreased.Geostatistic analysis can reveal the spatial variability of soil characteristics in three layers.The spatial correlation of CO₃^2-content on the 30～50cm layer, HCO₃^- content on the 10～30cm,30～50cm layers, SO₄^2-content on the 0～10cm,10～30cm layer, soil moisture on three layers were weak, showing the random factors, such as fertilization,farming measures and cultivation system, played a leading role in their spatial variation. The spatial correlation of Ca²⁺ and Mg²⁺content on 30～50cm layer, CI-content on 0～10cm layer were strong, and structural factors, such as climate,parent material,topography,soil type, made up a major position in their spatial variation.The spatial correlation of ther salt ions on other soil layers and the soil pH value on three layers were medium, and their spatial variations were affected by both random factors, such as fertilization,farming measures and cultivation system, and structural factors, such as climate,parent material,topography,soil type at the same time.Correlation analysis between growth of phragmites australis and soil characteristics showed that soil pH value on three layers all had suppressive effect on the growth of phragmites australis, and its effect was distinct on the underlayer. Except from the Mg²⁺content on 10～30cm,30～50cm layers, CO₃^2-,HCO₃^-content on 30～50cm layer had stimulative effect on the coverage of phragmites australis, other salt ions had suppressive effect on it. The suppressive effect of salt ions on phragmites australis decreased with the increase of soil depth.The Mg²⁺,Ca²⁺,CI-,HCO₃^-,SO₄^2-content on 0～10cm layer, CO₃^2-content on 0～10cm,10～30cm layer had suppressive effect on the height of phragmites australis while other salt ions on other soil layers had stimulative effect on it. And this stimulative effect increased with the increase of soil depth.The Na⁺+K⁺content on 30～50cm layer, SO₄^2-content on 0～10cm,30～50cm layer had suppressive effect on the crown of phragmites australis, and other salt ions on other soil layers had stimulative effect on it. And their stimulative effect on it decreased with increase of soil depth.The Na⁺+K⁺content on 0～10cm layer, Mg²⁺content on 30～50cm layer, Ca²⁺ content on 10～30cm layer, CO₃^2-,HCO₃^-content on 10～30cm,30～50cm layer, SO₄^2-content on 30～50cm layer had suppressive effect on the density of phragmites australis while other salt ions on other soil layers had stimulative effect on it. And their stimulative effects decreased with the increase of soil depth.The soil moistures on three layers had stimulative effects on the growth of phragmites australis. Its stimulative effect on the coverage,height,density of phragmites australis is not so distict, but its stimulative effect on the density of phragmites austalis was distict. And that stimulative effect increased with the increase of soil depth.