Soil hydraulic properties are essential for understanding soil hydrological and erosion processes. The importance of roots on soil hydraulic parameters has been widely recognized, but current studies have focused mainly on the root effect of a single plant species. However, few studies have been carried out to investigate the effect of mixed plant roots on soil hydraulic parameters. Undisturbed soil samples were collected from three natural sampling sites with single plant types and four sites with mixed plant types. Both soil hydraulic parameters were measured: soil saturated hydraulic conductivity (Ks) and soil saturated water content (SW). Then the root effects on Ks and SW were subsequently evaluated. The results showed that the Ks and SW at the sites with mixed plants were higher than those at the sites with a single plant species. At all the sites, Ks and SW both exhibited a decreasing-increasing-decreasing trend with increasing root density. The critical root density for the above change was quantified. When fibrous roots were mixed with tap roots, Ks was mainly affected by tap roots, while SW was mainly affected by fibrous roots. The influence of roots on Ks and SW was mainly achieved by affecting soil organic matter, not by directly affecting Ks and SW. Based on the root density, the herbaceous coverage with optimal saturated hydraulic conductivity and water content was estimated to be 66.71%.

中文翻译：

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混合植物根系对黄土区土壤饱和导水率和饱和含水量的影响

土壤水力特性对于了解土壤水文和侵蚀过程至关重要。根系对土壤水力参数的重要性已被广泛认识，但目前的研究主要集中在单一植物物种的根系效应上。然而，很少有研究探讨混合植物根系对土壤水力参数的影响。原状土壤样品是从三个单一植物类型的自然采样点和四个混合植物类型的自然采样点采集的。测量了两个土壤水力参数：土壤饱和导水率（Ks）和土壤饱和含水量（SW）。然后评估根对 Ks 和 SW 的影响。结果表明，混合植物位点的Ks和SW均高于单一植物位点。在所有站点，随着根密度的增加，Ks和SW均呈现出减少-增加-减少的趋势。对上述变化的临界根密度进行了量化。当须根与直根混合时，Ks主要受直根影响，而SW主要受须根影响。根系对Ks和SW的影响主要是通过影响土壤有机质来实现的，而不是直接影响Ks和SW。根据根系密度，估计最佳饱和导水率和含水量的草本覆盖率为66.71%。