Abstract The effects of vegetation restoration on the hydraulic processes of steep colluvial deposits at collapsing gullies in South China have rarely been evaluated. This study quantified the influences of canopy, biocrusts, and roots on 30° deposit slopes planted with Melinis minutifora and Chrysopogon zizanioides via rainfall simulation experiments. Intact M. minutifora and C. zizanioides effectively decreased flow velocities (v) by 35.3% and 29.5%, and increased Darcy–Weisbach friction coefficients (f) by 239.6% and 130.8% compared to that of the control treatments, respectively. The roots of M. minutifora contributed most to the decrease of v and the increase of f, while roots and canopy of C. zizanioides decreased v and increased f to the greatest extents, respectively. Biocrusts increased f and decreased v for all rain intensities when they were combined with roots. However, when they grew on bare slopes, these positive effects were only observed in response to 60 mm h−1 rain events, but were reversed for 120, and 180 mm h−1 rain events. Canopy decreased flow shear stress (τ) and stream power (ω), while roots showed a contrasting result, and the effects of biocrusts varied on different slopes. The influences of plants and components also varied with rain intensities. Sediment yield rates showed significant relationships with v, Re, τ, and ω and could be predicted using linear regression of τ or ω. This study highlights the effects of canopies, roots of different vegetation types, and biocrusts on the hydraulic process on steep colluvial deposit. The presented results aid the decision-making and management of vegetation restoration of collapsing gullies.

中文翻译：

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植被陡峭红壤崩积沉积物对近土壤表面成分的流动水力响应

摘要 植被恢复对华南崩塌沟壑陡坡沉积物水力过程的影响鲜有评价。本研究通过降雨模拟实验量化了冠层、生物地壳和根系对种植了小蜂花和金针菇的 30°沉积坡度的影响。与对照处理相比，完整的 M. minutifora 和 C. zizanioides 有效地将流速 (v) 降低了 35.3% 和 29.5%，并将 Darcy-Weisbach 摩擦系数 (f) 分别提高了 239.6% 和 130.8%。M. minutifora 的根对 v 的减少和 f 的增加贡献最大，而 C. zizanioides 的根和冠层分别最大程度地减少了 v 和增加了 f。当生物结皮与根结合时，对于所有降雨强度，生物结皮都会增加 f 并减少 v。然而，当它们在裸坡上生长时，这些积极影响仅在 60 mm h-1 降雨事件中观察到，但在 120 和 180 mm h-1 降雨事件中被逆转。冠层降低了流切应力 (τ) 和水流功率 (ω)，而根部显示出相反的结果，生物结皮的影响在不同坡度上有所不同。植物和成分的影响也随着降雨强度的变化而变化。沉积物产率显示出与 v、Re、τ 和 ω 的显着关系，并且可以使用 τ 或 ω 的线性回归进行预测。本研究强调了冠层、不同植被类型的根部和生物地壳对陡峭崩积沉积物的水力过程的影响。