松嫩平原北部典型黑土剖面黏土矿物组成及其环境指示意义

通过野外调查、土壤化学成分分析、土壤黏土矿物X-射线衍射(XRD)图谱分析和土壤风化程度分析,对松嫩平原北部黑土区大豆/玉米轮作农田、林地、草地、退耕还林等多种土地利用方式土壤剖面黏土矿物组成进行研究,探究不同土地利用方式下土壤剖面化学成分、黏土矿物组成以及风化程度变化规律及其对环境的指示意义。结果表明:不同土地利用方式土壤剖面中钾、钠、钙元素含量依次为草地>耕地>林地>荒地;在剖面60 cm以上有机碳含量为耕地>林地>草地>荒地,60~80 cm以下,有机碳含量为荒地>草地>林地>耕地。研究区不同土地利用方式土壤风化程度依次为退耕、荒地>林地>耕地>草地;土壤淋溶程度为荒地>草地、林地>耕地。研究区不同土地利用类型土壤总体上黏土矿物以蒙脱石、高岭石、蛭石、水云母和绿泥石为主,其中耕地、林地以2:1型非膨胀性黏土矿物为主,草地以2:1型膨胀性黏土矿物为主,荒地以1:1型黏土矿物为主。通过研究区不同土地利用类型的黏土矿物组合及其含量对比,结合剖面的风化程度计算,得出随着风化程度和成土作用的加深,土壤中绿泥石等矿物向高岭石、蒙脱石转化,水云母向蛭石转化,而其环境条件也由干冷转为湿热气候。

The clay mineral composition and environmental implications of the typical black soil profiles of the northern Songnen Plain

This study investigated the clay mineral composition of the soil profiles of cropland for soybean/maize rotation, forest land, grassland, and farmland returned to forest in the black soil regions of the northern Songnen Plain through field investigation, the analysis of soil chemical composition, the X-ray diffraction (XRD) spectrum analysis of soil clay minerals, and the analysis of soil weathering degree. The purpose of this study is to explore the chemical composition, clay mineral composition, and weathering change patterns of the soil profiles of the land for different uses and their environmental implications. The results show that in the soil profiles, the land for different uses is in the order of grassland > cropland > forest land > wasteland regarding the potassium, sodium, and calcium contents, in the order of cropland > forest land > grassland > wasteland regarding the organic carbon content in the soil at a depth less than 60 cm, in the order of wasteland > grassland > forest land > cropland regarding the organic carbon content in the soil at a depth greater than 60~80 cm, in the order of farmland returned to forest and wasteland > forest land > cropland > grassland regarding the soil weathering degree, and in the order of wasteland > grassland and forest land > cropland in terms of the soil leaching degree. The clay minerals in the soil of land for different uses area mainly consist of montmorillonites, kaolinites, vermiculites, hydromicas, and chlorites. The cropland, forest land, grassland, and wasteland are dominated by the 2:1 type of non-expansive clay minerals, the 2:1 type of non-expansive clay minerals, the 2:1 type of expansive clay minerals, and the 1:1 type of clay minerals, respectively. As shown by the comparison of the clay mineral assemblages and their contents in the soil of land for different uses in the study area, as well as the calculation of the weathering degree of the soil profiles, minerals such as chlorites in the soil transition to kaolinites and montmorillonites, hydromicas transition to vermiculites, and the environment has changed from a dry and cold climate to a wet and hot climate as the weathering degree and pedogenesis deepen.