黏土矿物组成对天山北坡土壤变性特征的影响

Effects of Clay Mineral Composition on Vertic Characteristics in the Northern Slope of Tianshan Mountain

【目的】调查天山北坡是否分布有变性特征的土壤,通过测定其黏土矿物组成,探讨新疆变性土壤发育的内在矿物学机制。【方法】使用传统野外调查方法,研究天山北坡11个土壤剖面,根据裂隙、滑擦面、楔状结构等诊断特性的发育状况划分其变性化程度。测定了研究剖面28个土壤发生层的线胀系数和黏土矿物中蒙皂石的含量,并探讨其相关性。【结果】研究的11个土壤剖面中有4个剖面可相对划分为强变性化的土壤,28个土层蒙皂石含量的平均值为38%。强变性化程度土壤中蒙皂石的含量显著高于弱变性化程度的土壤。蒙皂石含量与线胀系数之间存在极显著的幂函数关系。【结论】较低的蒙皂石含量是决定本研究调查的土壤变性化程度不高的内在原因。未来在新疆开展变性土调查时,需要重点考虑蒙皂石含量高的成土母质分布区。

[ Objective] To investigate whether there are vertie soils existing in the northern slope of Tianshan Mountain and explore the internal mineralogical mechanism of vertie soils in Xinjiang by measuring clay mineral composition. [ Method ] Eleven soil profiles in the northern slope of Tianshan Mountain were studied using traditional field survey approaches. Development degree of soil vertic characteristics was determined according to diagnostic criteria such as cracks, slickenside and wedge -shaped soil aggregates, coefficient of linear extensibility （COLE） and smectite content in clay mineral of 28 soil layers were measured, and their correlation was discussed. [ Result ] Among the eleven studied soil profiles, four could be relatively classified as soils with strongly developed vertic characteristics. The mean smeetite content of the 28 soil layers was 38%. Smectite contents of soils with strongly developed vertic characteristics were significantly higher than those of soils with slightly developed vertie characteristics. A significant power relationship existed between smectite content and COLE. [ Conclusion] Low smectite content is the internal mechanism that determines the low development degree of soil vertie characteristics in this study. Distribution area of parent material with high smectite content should be especially considered when surveying vertisols in Xinjiang in the future.