桂东南花岗岩红壤区典型崩岗剖面风化强度对理化特性的影响

Effect of Weathering Intensity on Physical and Chemical Properties of Typical Benggang Profile in Granite Red Soil Area of Southeast Guangxi

[目的]花岗岩红壤剖面风化强度与崩岗形成密切相关,促进崩岗侵蚀的发育和扩张,研究风化强度和理化特性对崩岗的作用机理,可为花岗岩崩岗科学防治提供理论依据。[方法]选取花岗岩红壤区典型崩岗剖面为研究对象,测定不同土层的常量氧化物含量和土壤理化性质,分析花岗岩红壤风化强度对理化特性的影响。[结果](1)土壤剖面常量氧化物组成以SiO_(2)、Al_(2)O_(3)和Fe_(2)O_(3)为主,花岗岩风化壳表现出脱硅富铁铝化过程,风化强度随土壤剖面深度增加而降低,处于高等风化阶段。(2)土壤剖面的理化性质具有异质性。表层有机质、阳离子交换量、黏粒含量和饱和导水率高,黏结性和持水性强;下层砂粒含量高,结构松散,透水性强。(3)相关性和通径分析结果表明,风化强度与非毛管孔隙度、有机质、阳离子交换量、黏粒含量、饱和导水率、界限含水率呈正相关,Fe_(2)O_(3)对黏粒含量、砂粒含量和界限含水率的综合决定性能力最强。(4)表层风化强度高,黏粒比例高,对水的吸附能力强,土壤颗粒间的胶结作用强,土体稳定性好。下层风化强度低,胶结物质含量和界限含水率低,土体抗蚀性差,当土体暴露或者水蚀的条件下,容易崩塌形成崩岗。[结论]土壤剖面风化强度对理化特性产生影响,是促进崩岗形成的重要影响因素。

[Objective]The weathering intensity of granite red soil profile is closely related to the formation of Benggang,which promotes the development and expansion of Benggang.Studying the mechanism of weathering intensity and physicochemical properties on Benggang can provide a theoretical basis for the scientific prevention and control of granite Benggang.[Methods]The typical Benggang profile of granite red soil areas was selected as the research object,the oxide content and physicochemical properties of different soil layers were measured,and the influence of weathering intensity on the physicochemical properties of granite red soil was analyzed.[Results](1)The major element oxides in the soil profile were mainly composed of SiO_(2),Al_(2)O_(3)and Fe_(2)O_(3).The weathering crust of granite showed the process of desilication and iron-rich aluminization.The weathering intensity decreased with the increase in the depth of the soil profile,which was in the stage of high weathering.(2)The physical and chemical properties of the soil profile exhibited heterogeneous.The surface layer was characterized by high organic matter,cation exchange capacity,clay content and saturated hydraulic conductivity,with strong cohesiveness and water holding capacity;whereas the lower layer had high sand content,loose structure and strong water permeability.(3)The results of correlation and path analysis indicated that weathering intensity was positively correlated with non-capillary porosity,organic matter,cation exchange capacity,clay content,saturated hydraulic conductivity and boundary water content.Fe_(2)O_(3)had the strongest comprehensive determinative ability for clay content,sand content and boundary water content.(4)The surface weathering intensity was high,with a high proportion of clay,strong water adsorption capacity,strong cementation between soil particles,and good soil stability.The lower layer had a low of weathering intensity,with low content of cementing materials and boundary water content,poor soil corrosion resistance.When the soil was exposed or subjected to water erosion,it easily collapsed,forming Benggang.[Conclusion]The weathering intensity of soil profile has an impact on the physicochemical properties,which is an important factor to promote the formation of Benggang.