塔里木河上游绿洲土壤表层盐分特征及其影响因子分析

选择塔里木河上游阿拉尔垦区,以农田、新开农田、撂荒地、人工林、天然林、盐碱地及荒草地等不同土地利用类型的样地土壤为研究对象,结合通径分析,研究了土壤中w(全盐)与盐源分布、盐分化学特性、土壤理化特性、地下水等影响因子的分布规律及相互关系. 结果表明,该区域盐分表聚特征明显,土壤表土层w(全盐)远大于心土层和底土层,各土地利用类型表土层w(全盐)表现为盐碱地最高(平均值为52.93g/kg),盐碱地>天然林>人工林>荒草地>撂荒地>农田>新开农田. 由通径分析结果可知,S_20-50〔心土层w(全盐)〕、SAR(钠吸附比)、SDR(钠钙镁比)、D_g(地下水埋深)、c(Cl-)/c(SO₄2-)、c(HCO₃-)、pH、ρ(土壤容重)、S_50-80〔底土层w(全盐)〕、SSP(可溶性钠百分率)对表土层w(全盐)的直接通径系数依次为0.415、0.414、-0.344、-0.201、0.200、0.162、0.092、-0.086、0.080、0.071. 土壤盐源分布和土壤盐分化学特性对表土层w(全盐)影响较大,其次是D_g,土壤理化特性对表土层w(全盐)影响相对较小. 反映盐源分布的S_20-50和反映土壤盐分化学特性的SAR是表土层w(全盐)的主要控制因子. 

Characteristics of Surface Soil Salinity and Impact Factor Analysis for the Oasis in the Upper Reach of the Tarim River

Salinization of irrigated lands is a common phenomenon wherever irrigation is practiced under arid or semi-arid conditions. In arid land, salinization affects the sustainability of irrigation systems through causing significant degradation of soil resources. A case study was carried out in Alar irrigated area of Xinjiang Province to reveal the characteristics of total salt in the surface soil for different types of land uses (e.g., cropland, new cultivated cropland, abandoned land, plantation, natural forest, saline-alkali land and grassland). The path coefficient between total salt in the surface soil and their impact factors were also analyzed. The results showed that the total salt in the surface soil was higher than those in the subsoil and substratum soil, and this indicated a salt accumulation trend in the surface soil. The total salt content in the surface soil of saline-alkali land (52.93g/kg) was highest between different types of land uses. The decreasing order of the total salt content in the surface soil was:saline-alkali land > natural forest > plantation > grassland > abandoned land > cropland > new cultivated cropland. Path analysis showed that the path coefficients between the total salt contents in the surface soil and other properties could be arranged as:S20-50(0.415), SAR(0.414), SDR(-0.344), D_g(-0.201), concentration ratio of Cl-and SO₄2-(0.200), concentration of HCO₃-(0.162), pH(0.092), soil density(-0.086), S50-80(0.080) and SSP(0.071). In addition, the salt source distribution and chemical properties of ionic composition had the greatest contribution to salt accumulation in the surface soil. The direct path coefficients of total salt content in the subsoil and sodium adsorption ratio (SAR) were 0.415and 0.414respectively. The impact of ground water depth was less significant to the total salt content in the surface soil, and that of the soil physicochemical was the least significant. The total salt content in the surface soil and SAR showed that chemical properties of ionic composition were two primary factors of salt accumulation in surface soil.