黄土高原藓结皮覆盖土壤的穿透阻力特征及其影响因素

Characteristics of Penetration Resistance of Moss-dominated Biocrusts on Aeolian and Loessal Soils and Its Influencing Factors on Chinese Loess Plateau

生物结皮的发育显著地影响并改变了表层土壤的理化性状,从而影响土壤穿透阻力。为探明生物结皮层对土壤穿透阻力的影响,针对黄土高原风沙土和黄绵土两种典型土壤,利用高精度土壤贯入仪测定并比较了不同含水量下藓结皮土壤和无结皮土壤的穿透阻力差异,定量分析了藓结皮层对土壤穿透阻力的影响及其与土壤性质(含水量、容重和有机质含量以及颗粒组成)的关系。结果表明:风沙土和黄绵土藓结皮层最大穿透阻力的变化范围为0.38~3.74 MPa和0.43~8.01 MPa,分别为同等深度下无结皮土壤的2.14~9.45倍(P=0.001)和1.38~6.27倍(P=0.051)。藓结皮对风沙土穿透阻力的影响深度为表层2~12 mm(P=0.028),而对黄绵土的影响深度为3~24 mm(随含水量变异较大)。同时,与无结皮土壤的穿透阻力随深度增加而线性增加的趋势不同,藓结皮土壤的穿透阻力随深度增加在结皮层呈先增后减的趋势,在结皮下层呈线性增加的趋势。此外,藓结皮土壤的横向穿透阻力和纵向穿透阻力差异显著(P≤0.03),但在无结皮土壤上差异不显著(P≥0.052)。藓结皮土壤的穿透阻力与含水量呈显著的幂函数关系(P<0.001),与容重、有机质含量以及砂粒含量呈线性关系,这些因素均为藓结皮改变表层土壤穿透阻力的重要途径。

The development of biocrust significantly affect and change the physiochemical properties of the surface soil,which in turn affects the penetration resistance.In order to investigate the effect of biocrust on soil penetration resistance,this study took moss-dominated biocrusts and bare soils from aeolian and loessal soils on the Loess Plateau as the test materials,compared the differences in penetration resistance between biocrusts and bare soils,and investigated their differences in penetration resistance under different water contents by using the high precision soil penetrometer.At the same time,the influence of biocrusts on soil penetration resistance and its relationship with soil properties(water content,bulk density,organic matter content,particle composition)were quantitatively analyzed.The results showed that the maximum penetration resistance was 0.38–3.74 MPa for aeolian soil with biocrust and 0.43–8.01 MPa for loessal soil with biocrust,which was about 2.14 to 9.45 times(P=0.001)and 1.38 to 6.27(P=0.051)times of the same depth of aeolian and loessal soils without crust,respectively.The effect of moss crust on the penetration resistance of aeolian soil was 2 to 12 mm(P=0.028),while the depth of influence on loessal soil varied greatly under different water contents,ranging from 3 to 24 mm.At the same time,the penetration resistance of the bare soil increased linearly with the increase of soil depth.The penetration resistance of soil with biocrust increased first and then decreased with the increase of depth in the crust layer,while it was linear in the lower layer of the crust.In addition,the lateral and the longitudinal penetrating resistances were significantly different(P≤0.03)for soil with the biocrust,but not significant for soil without crust(P≥0.052).The penetration resistance of soil with biocrust had a significant power function relationship with water content(P<0.001),but was linearly correlated with bulk density,organic matter and sand contents.These factors are important ways for the biocrust to change the penetration resistance of the surface soil.