黄土高原生物结皮覆盖对土壤积水入渗特征的影响及其模型模拟

Effects of biocrust covering on soil water infiltration characteristicson the Loess Plateau and its simulation

【目的】探讨生物结皮层覆盖后对土壤水分入渗特征的影响。【方法】于2018年7-8月,以位于陕北黄土高原神木市六道沟小流域的生物结皮覆盖的黄绵土和风沙土为研究对象,以相邻的无结皮黄绵土和风沙土为对照(距离在10 m以内),采用双环法和土柱法分别对其水分入渗特征进行测定,计算饱和导水率(K s)、土壤水分入渗速率及土壤水分入渗参数(稳定入渗速率、平均入渗速率和累积入渗量),并采用Philip模型、Kostiakov模型和Horton模型对水分入渗过程进行模拟。【结果】(1)无论是黄绵土还是风沙土,生物结皮均能降低不同土层土壤的K s,且生物结皮对黄绵土的影响高于风沙土。在0~20 cm土层,与无结皮对照相比,生物结皮覆盖的黄绵土和风沙土上K s平均分别下降了42.1%和25.6%。(2)基于双环法和土柱法的测定结果显示,在积水入渗条件下,生物结皮覆盖黄绵土的稳定入渗速率(0.29~0.55 mm/min)、平均入渗速率(0.57~0.58 mm/min)和累积入渗量(3.63~3.69 cm)与无结皮黄绵土相比分别减少了27.5%~45.0%,32.6%~58.4%和31.8%~61.0%;生物结皮覆盖风沙土的稳定入渗速率(3.30~4.13 mm/min)、平均入渗速率(3.06~4.25 mm/min)和累积入渗量(19.22~26.76 cm)与无结皮风沙土相比分别减少了2.4%~11.3%,1.6%~27.8%和5.5%~26.3%,且基于双环法测定的土壤水分入渗参数整体上略高于土柱法。相对黄绵土,生物结皮对风沙土水分入渗参数的影响较小。(3)不同模型的模拟结果表明,Horton模型对生物结皮覆盖土壤水分入渗过程的拟合效果整体优于Philip模型和Kostiakov模型。【结论】生物结皮层的覆盖降低了0~20 cm土层的渗透性,土壤水分入渗过程可以使用Horton模型进行拟合。

【Objective】This study was conducted to understand the effects of biocrusts on soil water infiltration and hydropedological processes.【Method】In this study,biocrusts on loess soil and aeolian sand were measured in a watershed named Liudaogou in the Loess Plateau in Northern Shaanxi during July to August 2018 using adjacent loess soil and aeolian sand within 10 m as control.The water infiltration characteristics of different treatments were measured from initial to steady state by the double ring and soil column methods,respectively.The saturated hydraulic conductivity(K s),water infiltration rate and water infiltration parameters(stable infiltration rate,average infiltration rate and cumulative infiltration)were calculated,and the water infiltration process was simulated by Philip model,Kostiakov model and Horton model,respectively.【Result】(1)Biocrusts decreased K s of different soil layers for both loess soil and aeolian sand,and the effect of biocrusts on the loess soil was larger than that on aeolian sand.The K s of biocrusts(0-20 cm)with loess soil and aeolian sand was averagely decreased by 42.1%and 25.6%as compared to the corresponding soils without biocrusts.(2)In comparison to the loess soil,the stable infiltration rate(0.29-0.55 mm/min),average infiltration rate(0.57-0.58 mm/min),and cumulative infiltration(3.63-3.69 cm)of the biocrusts on loess soil was decreased by 27.5%-45.0%,32.6%-58.4%,and 31.8%-61.0%,respectively.Correspondingly,as compared with the aeolian sand the stable infiltration rate(3.30-4.13 mm/min),average infiltration rate(3.06-4.25 mm/min),and cumulative infiltration(19.22-26.76 cm)of the biocrusts on aeolian sand was decreased by 2.4%-11.3%,1.6%-27.8%,and 5.5%-26.3%,respectively.The infiltration parameters measured by the double ring were higher than that measured by the soil column.Moreover,compared with loess soil,biocrusts had less effect on the infiltration parameters of aeolian sand.(3)The Horton model performed better than the Kostiakov and Philip models in the simulation of biocrust infiltration processes.【Conclusion】The presence of biocrust layer decreased the permeability of soil(0-20 cm)and the infiltration process can be simulated by Horton model.