季节性冻融对土壤可蚀性影响的试验研究

发布时间：2018-01-25 04:18

  本文关键词： 季节性冻融 冻融循环 广义土壤结构指数 土壤三相结构距离 土壤可蚀性　出处：《西北农林科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：黄河中游地区,属于温带中纬度地区,该区冻土层解冻时期产生的土壤流失量占全年土壤流失量的50%以上,是研究季节性冻融条件下土壤可蚀性变化的典型区域,然而该区域关于冻融作用对土壤可蚀性的研究相对较为薄弱。本研究以季节性冻融区典型风沙土、褐土、黑垆土、黄绵土为例,通过室内模拟冻融试验,测定土壤理化性质的变化,研究冻融作用对土壤可蚀性的影响,并运用EPIC模型估算土壤可蚀性K值,分析冻融作用对土壤可蚀性因子K值的定量影响,构建冻融作用前后土壤可蚀性K值的关系式,探讨土壤可蚀性对冻融作用的响应机制,为冻融作用下坡耕地土壤侵蚀的机理研究奠定基础,并以期为季节性冻融区土壤侵蚀防治提供理论依据和科学指导。所得主要结论如下:(1)季节性冻融作用显著影响土壤理化性质,影响程度与冻融循环次数、土壤初始含水率和土层深度有关。风沙土、褐土、黑垆土、黄绵土的含水率、土壤孔隙度、土壤容重、粘粒含量、砂粒含量、微团聚体含量、土壤团聚度、分散率、土壤硬度和土壤抗剪强度、有机质含量等变化在前9次冻融循环过程中,各次冻融循环之间均有显著差异(P0.05),而9次循环后变化幅度减小,每次冻融循环之间差异性不显著(P0.05);冻融循环过程中高含水率土壤的理化性质变化较低含水率土壤更为明显,表明高含水率土壤对冻融作用的响应更为剧烈;冻融作用对表层土壤(0~5 cm)的破坏最严重,表层土壤的理化性质变化与深层土壤相比均有显著性差异(P0.05),。(2)季节性冻融作用显著增加了土壤可蚀性K值,土壤可蚀性K值的变化程度主要受冻融循环次数及土壤类型影响。冻融循环过程中土壤可蚀性K值呈现整体增加趋势,风沙土、褐土、黄绵土可蚀性K值与冻融循环次数(1~15次)呈现对数函数关系。在1~5次冻融循环过程中风沙土可蚀性K值变化幅度较大,风沙土经5次冻融后土壤可蚀性K值增加了0.0376[t ha h/(ha MJ mm)],与未冻融(0次)土壤相比增加了19.00%,15次冻融循环后风沙土可蚀性K值增加了20.55%;0~9次冻融循环过程中,褐土、黄绵土可蚀性K值增加幅度较大,褐土、黄绵土可蚀性K值在9次循环后土壤可蚀性K值分别增加了:7.37%、9.45%,15次冻融循环后土壤可蚀性分别增加了:10.57%、11.79%;黑垆土可蚀性K值在冻融循环过程中的变化无明显规律,但随着冻融循环次数的增加,总体表现增加趋势,黑垆土可蚀性K值在15次冻融循环后增加了2.77%;冻融后的土壤可蚀性K值约为未冻融土壤可蚀性K值的1.173倍,即:K_(冻融)=1.173K_(未冻融)。(3)季节性冻融作用一方面破坏土壤团聚体,降低土壤团聚度、土壤粘粒含量、土壤容重、广义土壤结构指数及土壤物理学特性,另一方面增加土壤有机质含量、砂粒含量、粗粉粒含量、中值粒径d50、土壤分散率,通过这两方面作用,使得土壤可蚀性K值呈现不同程度的增加。冻融作用显著降低土壤粘粒、增加土壤砂粒含量,降低大粒径微团聚体含量而增加小粒径微团聚体含量,导致土壤砂化,土壤团聚度降低,分散率增加;冻融循环显著降低土壤容重、土壤硬度及土壤抗剪强度,增加土壤含水率、土壤孔隙度、有机质含量,从而降低土壤抵抗外界营力破坏的能力;冻融循环后影响土壤可蚀性的首要主导因子为土壤团聚体含量,粘粒含量、砂粒含量、粉粒含量次之,然后依次是土壤有机质含量、土壤容重及孔隙度等;影响季节性冻融区土壤可蚀性的因子可以概化为:土壤质地、有机质因子,土壤团聚作用因子及土壤三相结构因子。
[Abstract]:In the middle reaches of the Yellow River, which belongs to the temperate latitudes, the area of permafrost thawing period, soil erosion amount accounted for more than 50% of the amount of soil loss, is the study of seasonal freezing and thawing conditions of typical area of soil erodibility changes, however, the area about freeze-thaw action research on soil erodibility is relatively weak in this paper, seasonal freeze-thaw area of typical aeolian sandy soil, cinnamon soil, loessial soil, loessial soil as an example, through the indoor simulated freeze-thaw test, determination of soil physical and chemical properties, can affect the corrosion resistance of soil freezing and thawing, and use EPIC model to estimate soil erodibility K value can be. The quantitative effects of erodibility factor K value analysis on soil freezing and thawing, construction of freezing and thawing soil before and after the relationship between erodibility K value of soil erodibility, the freeze thawing response mechanism, for freezing and thawing slope land soil erosion mechanism of The foundation, and in order to seasonal freezing and thawing soil erosion prevention and provide theoretical basis and scientific guidance. The main conclusions are as follows: (1) effects of seasonal freezing and thawing significantly affected the soil physicochemical properties, the influence degree and the number of freeze-thaw cycles, with initial soil water content and soil depth. Sandy soil, cinnamon soil. Loessial soil, soil water content, soil porosity, soil bulk density, clay content, sand content, soil micro aggregate content, degree of aggregation, dispersion rate, shear strength of soil hardness and soil organic matter content changes in the first 9 freeze-thaw cycles during the freeze-thaw cycles were between significant differences (P0.05), and after 9 cycles reduced the amplitude of variation, each freeze-thaw cycle not significant difference between them (P0.05); freezing thawing soil physical and chemical properties of high moisture cycle in low water content of soil is more obvious, showed high water content on soil freezing and thawing 浣滅敤鐨勫搷搴旀洿涓哄墽鐑，

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