Plant roots interact closely with soils and significantly affect soil erosion, which can be reflected in various root traits. Slope gradient is a topographic factor that considerably affects the interactions between root traits and soil erosion. However, little is known about the relationships between root traits and soil erosion, which are affected by slope gradient. This study investigated the responses of root traits and soil detachment to variable slope gradients in a representative purple-soil sloping grassland. Topsoil samples with vetiver ( L.) roots (VT) and without roots (CK) were collected at three gradients (20°, 30°, and 40°) to determine the soil detachment capacity, the rill erodibility and critical shear stress. The root mass and morphology of the VT were also measured. The results showed that root mass density and root morphological traits related to the total roots (irrespective of root diameter) and roots with diameter ≤ 1.0 mm decreased markedly from 20° to 30°. The proportions of root morphology with diameter > 1.0 mm increased as slope gradients increased, suggesting that steep slopes could promote coarse roots. The soil detachment capacity was 34.1–49.6 % lower in VT than in CK under studied slope gradients, whereas these reductions did not differ with slope gradients. Lower rill erodibility and higher critical shear stress were found in VT under each slope than in CK, highlighting the role of roots in enhancing soil erosion resistance. Our results contribute to understanding the mechanisms by which roots on control soil water erosion in complicated, changing environments.

中文翻译：

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典型紫色土坡地草地根系性状及土壤脱离对坡度变化的响应

植物根系与土壤相互作用密切，对水土流失有显着影响，这可以体现在根系的各种性状上。坡度梯度是一个地形因素，对根系性状与土壤侵蚀之间的相互作用有很大影响。然而，人们对根系性状与土壤侵蚀之间的关系知之甚少，土壤侵蚀受坡度影响。本研究调查了代表性紫色土坡度草地根系性状和土壤脱离对不同坡度梯度的响应。在三个梯度（20°、30°和40°）下收集有香根草（L.）根（VT）和无根（CK）的表土样品，以确定土壤脱离能力、细沟侵蚀性和临界剪切应力。还测量了 VT 的根质量和形态。结果表明，从20°到30°，与总根（不考虑根直径）和直径≤1.0 mm的根相关的根质量密度和根形态性状显着下降。随着坡度的增加，直径>1.0 mm的根形态比例增加，表明陡坡可以促进粗根。在所研究的坡度梯度下，VT 的土壤脱离能力比 CK 低 34.1-49.6%，而这些降低量并没有随坡度的变化而变化。在每个坡度下，VT 中的细沟侵蚀性均低于 CK，临界剪应力高于 CK，这凸显了根系在增强土壤侵蚀抵抗力方面的作用。我们的研究结果有助于理解根系在复杂多变的环境中控制土壤水侵蚀的机制。