砒砂岩区不同退耕还林措施土壤颗粒及交换性能分布特征

为研究砒砂岩区退耕还林还草措施下林地和草地的土壤结构及土壤交换性能对其措施的响应,选取柠条林、油松林、小叶杨林和本氏针茅草地为研究对象,并以荞麦坡耕地为对照,通过野外取样与室内试验相结合的方式,采用分形理论探究土壤粒径分布(PSD)、阳离子交换量(CEC)和交换性盐基总量(ECEC)及其组成(Na~+、K~+、Ca~(2+)、Mg~(2+))的分布特征,并分析其相关性关系。结果表明:(1)实施退耕还林措施后,草地和林地的PSD分布范围、非均一性、离散程度均高于坡耕地,且柠条林的土壤粉粒含量、PSD分布范围的增幅效果最显著(P0.05);土壤剖面垂直层次上,草地有利于增加表层土壤的细粒组分和粒径的分布范围,而林地更有利于对深层土壤粒径的改良与细化;(2)研究区交换性盐基组成主要以碱土金属为主(Ca~(2+)、Mg~(2+)),不同措施的土壤ECEC和CEC值由大到小依次为柠条林油松林小叶杨林草地坡耕地。草地表层土壤交换性能优于底层土壤,而林地与之相反;(3)黏、粉粒和细砂是决定研究区土壤交换性能的细粒土壤和粗粒土壤,粉粒是CEC、ECEC的主要贡献因子,多重分形维数可较好地描述土壤交换性能与土壤颗粒间的关系。不同措施以柠条林对土壤颗粒组成和土壤交换性能的改良效果最优。

Distribution Characteristics of Soil Particles and Exchangeable Capacity Under Grain for Green Project in Pisha Sandstone Area

In order to study the response of soil structure and soil exchangeable capacity of forest and grass to different measures of Grain for Green Project in Pisha sandstone area, we selected Pinus tabuliformis forest (YS), Caragana korshinskii forest (NT), Populus simonii forest (XY) and Stipa bungeana grassland (ZM) as the research objects and buckwheat slope farmland (QM) as the control. Multi-fractal theory was used to determine the soil particle size distribution (PSD), which measured the fractions of CEC, ECEC and the composition of ECEC (Na⁺, K⁺, Ca²⁺, Mg²⁺), as well as their distribution status and their correlations.The results showed that:(1) The PSD distribution, heterogeneity and dispersion of grassland and woodland were higher than those of sloping farmland after the implementation of conversion of cropland to forest. In the different soil profiles. Grassland was conducive to increasing the distribution range of fine-grained components and particle size of surface soil. However, in the improvement of the above indicators, woodland was more conducive to the deep soil. Moreover, the increase of soil silt contents and PSD distribution range in Caragana korshinskii forest were the most significant among all the measures (P<0.05). (2)In terms of soil exchangeability, alkaline earth metals (Ca²⁺, Mg²⁺) were the main components of exchangeable base in the studied area. The CEC and ECEC values of soil under different measures were ranked as NT > YS > XY > ZM > QM. The exchangeable capacity of grassland surface soil was better than that bottom soil, while that of woodland was opposite. (3)Clay, silt and fine sand were the fine-grained soils and coarse-grained soils that determine soil exchangeable capacity in the studied area, and silt content was the main contributing factor of CEC and ECEC values. Multifractal dimension could well describe the relationship between soil exchangeable capacity and soil particles. It was found that among all the measures of Grain for Green Project, Caragana korshinskii had the best improvement effect on soil particle composition and soil exchangeable performance.