Millimeter-scale spatial variability in soil water sorptivity: scale, surface elevation, and subcritical repellency effects
Millimeter-scale spatial variability in soil water sorptivity: scale, surface elevation, and subcritical repellency effects
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土壤吸水率的毫米级空间变异：尺度、表面高程和亚临界排斥效应
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
I. Young
中科院分区：
文献类型：
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作者：
P. Hallett;N. Nunan;J. T. Douglas;I. Young
最近的证据表明，减少水渗透可能与小规模的微生物和/或化学过程，导致亚临界水排斥。我们测量了一个大的完整的土壤块（0.9米宽，13米长，0.25米深）从草地网站的表面上的吸水性，并研究了表面海拔和防水性对吸水性的影响在毫米尺度。土块部分干燥至0.22 mm 3 mm-3，似乎很容易润湿，并且在任何含水量下都不是严重的防水剂。整个取样网格的吸水率范围为0.1 ~ 0.8 mm s-1/2，变异系数（CV）为0.57。通过比较水和乙醇的吸附性确定的拒水性也有很大变化（CV = 0.47）。对吸水性和排斥性测量结果的地质统计学分析发现，几乎没有空间自相关的证据，这表明局部变异程度很高。这些数据进行了比较，以获得更大规模的测量与传统的渗透仪在张力条件下（40毫米接触半径），和积水条件（37和55毫米半径环），其中大孔隙影响渗透异质性。较大规模的张力渗透仪测量值的变异较小，CV为0.22，而积水渗透仪测量值的变异较大，CV > 0.50，可能是因为大孔流的影响。收集的数据表面高程表明，积水入渗，但不张力入渗的表面地形的影响。结果表明，驱避性可以诱导水运输的空间变异性水平在小尺度相比，大孔诱导在更大的尺度。
Recent evidence suggests that reduced water infiltration may be linked to small scale microbial andlor chemical processes that cause subcritical water repellency. We measured water sorptivity on the surface of a large intact block of soil (0.9 m wide, 13 m long, 0.25 m deep) taken from a grassland site and examined the effects of surface elevation and water repellency on water sorptivity at the millimeter scale. The soil block was partially dried to 0.22 mm 3 mm -3 , appeared to wet readily, and is not severely water repellent at any water content. Water sorptivity varied from 0.1 to 0.8 mm s -1/2 across the sampling grid with a coefficient of variation (CV) of 0.57. Water repellency, determined by comparing water and ethanol sorptivities, also varied considerably (CV = 0.47). Geostatistical analyses of water sorptivity and repellency measurements found little evidence of spatial autocorrelation, suggesting a high degree of local variability. These data were compared to larger scale measurements obtained with conventional infiltrometers under tension conditions (40 mm contact radius), and ponded conditions (37 and 55 mm radius rings) where macropores influence infiltration heterogeneity. Larger scale tension infiltrometer measurements were less variable with a CV of 0.22, whereas ponded infiltrometer measurements were more variable, CV > 0.50, presumably because of the influence of macropore flow. Data collected on surface elevation showed that ponded infiltration but not tension infiltration was influenced by surface topography. The results suggested that repellency can induce levels of spatial variability in water transport at small scales comparable to what macropores induce at larger scales.