泰山山前平原土地利用方式对潮棕壤黏土矿物组成的影响

Effects of Land Use of Different Patterns on Soil Clay Mineral Compositions in Piedmont Plain of Mountain Tai

对泰山山前平原潮棕壤区小麦/玉米轮作农田、杨树林地和荒草地三种土地利用方式黏土矿物组成进行研究,探究不同土地利用方式下黏土矿物组成的变异规律与影响因素。通过野外样地调查、室内土壤黏粒提取及其黏土矿物的X-射线衍射图谱分析等方法分析黏土矿物组成及相关土壤指标。结果表明:三种利用方式土壤以伊利石(包括结晶好伊利石和结晶差伊利石)为主要矿物,次要矿物为蛭石和高岭石,混层矿物为少量矿物组成。荒草地表层土壤伊利石含量最高(75.8%),分别较农田和林地土壤提高26.4%、23.6%。下层土壤伊利石含量较表层土壤有显著降低,荒草地土壤的降低幅度较大。结晶好伊利石含量表征土壤的风化程度,荒草地、林地、农田土壤矿物的风化作用依次增强。蛭石含量在下层土壤的差异显著且较表层土壤含量高,含量由高到低依次为荒草地、农田、林地。荒草地土壤有机碳含量和钠质分散有机无机复合体含量较林地和农田土壤有显著降低。不同利用方式土壤黏粒中伊利石含量与蛭石含量之间相互转化,受土壤速效钾含量的调控。荒地建议开垦为林地或草地,促进土壤有机碳保持和有机无机复合体形成,抑制黏土矿物在土壤剖面的迁移。

【Objective】It is well known that soil clay minerals play an important role in sustaining soil fertility, and composition of soil clay minerals vary with vegetation and management systems and land use patterns. A field survey of the piedmont plain of Mountain Tai was carried out on variation of clay mineral composition in the aquic brown soil with land use, i.e. wheat-maize rotation, poplar plantation and barren land, its affecting factors and its relationship with soil fertility indices.【Method】Based on the field survey, soil samples were collected from the fields different in land use for extraction of < 2μm soil clay particle with pipette method and analysis of composition of the extracted clay and relevant indices with the X-ray diffraction(XRD) method. XRD was applied to the clay samples for XRD patterns after the samples were treated separately with(a) the magnesium saturation and air-drying method,(b)magnesium saturation followed glycerol salvation, or(c) potassium saturation and heating at 300℃ or 500℃method.【Result】Qualitative analysis of the experimental XRD patterns reveals that the soils, regardless of land use patterns, had illite as dominant clay mineral, which consisted of well crystallized illite(WCI)and poorly crystallized illite(PCI), vermiculite and kaolinite in the next, and mixed-layer minerals the least. Quantitative information of clay mineral fraction derived from the fitting procedure for the different sub-fractions allowed for determination of complex mineralogy of the < 2 μm clay fraction in the soil samples. Results show that the soil samples varied in percentage of clay mineral fractions with land use.The barren land was the highest in illite in the topsoil, reaching 75.8% and being, 26.4%, 23.6% than higher the agricultural soil and plantation respectively. The content of illite was significantly lower in the subsoil than the topsoil, especially for barren land. PCI varied similarly to illite in content. WCI content reflected weathering degree of the soil, hence it increased successively barren land to, plantation and agricultural soil. Vermiculite content in the topsoil was not significantly different between the three different land.However, it varied more remarkably in the subsoil than in the topsoil and in order of as barren land >agricultural soil > plantation. Kaolinite content was similar to vermiculite content in variation in the soils.Barren land soil was lower than the other two in soil organic carbon content and content of inorganicorganic complexes, too.【Conclusion】The content of illite in the soil negatively related to the content of vermiculite, but positively related to soil available potassium, which is attributed to the transformation between illite and vermiculite. The content of soil organic carbon and the formation of inorganic-organic complexes with sodium dispersion grows in agricultural soil as affected by tillage, fertilization, and so on,which inhabit movement of the clay minerals in the soil layer, enhance weathering of the soil minerals, and increase availability of the potassium embedded in illite. Nowadays more and more barren land is reclaimed into plantation and meadowland, thus increasing vegetation coverage and hence soil organic carbon content,and controlling erosion of the land.