Preferential flow is expected to provide an important pathway to replenish soil water at deep soil layers in arid or semiarid areas; however, few studies have addressed this topic, especially in semiarid Loess hillslopes. This study aimed to quantify the effect of stand origin and slope position on the contribution of preferential flow to total infiltration and spatial variations in water flow. A blue dye tracer experiment was conducted to visualize water flow in Robinia pseudoacacia plantation (PL), natural forestland (NF), and natural grassland (NG) at the upslope, midslope, and downslope, and semivariance analysis was used to determine spatial variability at the centimeter scale. The results showed that role of macropore flow was dominant in upslope and midslope, and larger in NF than that in PL and NG, due to presence of abundant root systems in the upper soil of NF. Moreover, contribution of preferential flow at the upper slope in NF was larger than that in PL. At the downslope, the role of rock fragments coverage at the downslope was emphasized, leading lateral flow dominant at the downslope in PL and NG. In addition, contribution of preferential flow and vertical variability of infiltration at the downslope in PL was higher than that in NF. The findings demonstrate that compared with PL, NF has a more positive impact on increasing infiltration and preferential flow that can replenish deep soil water, and reducing surface runoff and soil erosion. The presence of rock fragments coverage can make lateral flow dominant at the downslope on the Loess hillslope, related to water movement along the slope toward streams and catchment outlets.

中文翻译：

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黄土丘陵区林分原点和坡位对入渗方式和优先流的影响

预计优先流将为干旱或半干旱地区深层土壤水的补充提供重要途径。但是，很少有研究针对这一主题，特别是在半干旱的黄土丘陵地带。这项研究旨在量化林分原点和斜坡位置对优先流量对总入渗和水流量空间变化的贡献的影响。进行了蓝色染料示踪剂实验以可视化刺槐中的水流上坡，中坡和下坡的人工林（PL），天然林地（NF）和天然草地（NG），并使用半方差分析确定厘米级的空间变异性。结果表明，由于NF上层土壤中存在大量根系，大孔流作用在上坡和中坡占主导地位，而在NF中比在PL和NG中更大。而且，NF上坡优先流的贡献大于PL中优先流的贡献。在下坡处，强调了岩石碎片在下坡处的覆盖作用，从而在PL和NG的下坡处主导了侧向流动。此外，PL下坡的优先流动和入渗垂直变化的贡献高于NF。研究结果表明，与PL相比，NF对增加渗透和优先流动具有更积极的影响，可以补充深层土壤水，并减少地表径流和土壤侵蚀。岩石碎片覆盖的存在可以使黄土斜坡上的下坡处的侧向流动占主导地位，这与水沿着斜坡向溪流和集水口的流动有关。