Abstract The effects of vegetation cover on overland flow and erosion processes on hillslopes vary with vegetation type and spatial distribution and the different vegetation components, including the above- and below-ground biomass. However, few attempts have been made to quantify how these factors affect erosion processes. Field experimental plots (5 m × 2 m) with a slope of approximately 25° were constructed and simulated rainfall (60 mm hr−1) (Rainfall) and simulated rainfall combined with upslope overland flow (20 L min−1) (Rainfall + Flow) were applied. Three grass species were planted, specifically Astragalus adsurgens (A. adsurgens), Medicago sativa (M. sativa) and Cosmos bipinnatus (C. bipinnatus). To isolate and quantify the relative contributions of the above-ground grass parts (stems, litter cover and leaves) and the roots to reducing surface runoff and erosion, each of the three grass species was subjected to three treatments: intact grass control (IG), no litter or leaves (only the grass stems and roots were reserved) (NLL), and only roots remaining (OR). The results showed that planting grass significantly reduced overland flow rate and velocity and sediment yield, and the mean reductions were 21.8%, 29.1% and 67.1%, respectively. M. sativa performed the best in controlling water and soil losses due to its thick canopy and dense, fine roots. Grasses reduced soil erosion mainly during the early stage of overland flow generation. The above-ground grass parts primarily contributed to reducing overland flow rate and velocity, with mean relative contributions of 64% and 86%, respectively. The roots played a predominant role in reducing soil erosion, with mean contribution of 84%. Due to the impact of upslope inflow, overland flow rate and velocity and sediment yield increased under the Rainfall + Flow conditions. The results suggest that grass species on downslope parts of semi-arid hillslopes performed better in reducing water and soil losses. This study is beneficial for forage selection, allocation and management practices, such as forage harvesting, when implementing restoration strategies to control soil and water losses.

中文翻译：

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不同草成分在控制模拟降雨下山坡径流和侵蚀中的相对重要性

摘要 植被覆盖对山坡地表径流和侵蚀过程的影响因植被类型和空间分布以及不同植被成分（包括地上和地下生物量）而异。然而，很少有人尝试量化这些因素如何影响侵蚀过程。建造了大约 25° 坡度的田间试验地块 (5 m × 2 m) 并模拟降雨 (60 mm hr−1) (Rainfall) 和模拟降雨结合上坡地表流 (20 L min−1) (Rainfall +流）。种植了三种草种，特别是黄芪（A. adsurgens）、紫花苜蓿（M. sativa）和大波斯菊（C. bipinnatus）。分离和量化地上草部分（茎、凋落物覆盖和树叶）和根以减少地表径流和侵蚀，三种草种中的每一种都进行了三个处理：完整的草控制（IG），没有凋落物或树叶（仅保留草茎和根）（NLL )，并且只剩下根 (OR)。结果表明，植草显着降低了地表流速、流速和产沙量，平均降低量分别为21.8%、29.1%和67.1%。M. sativa 由于其厚实的树冠和密实的细根，在控制水土流失方面表现最佳。草减少了土壤侵蚀，主要是在地表径流产生的早期阶段。地上草部分主要有助于降低地表流速和速度，平均相对贡献分别为 64% 和 86%。根系在减少土壤侵蚀方面发挥了主要作用，平均贡献率为 84%。由于上坡流入的影响，在降雨+流量条件下地表流速和速度以及沉积物产量增加。结果表明，半干旱山坡下坡部分的草种在减少水土流失方面表现更好。在实施恢复策略以控制水土流失时，这项研究有利于草料的选择、分配和管理实践，例如草料收获。结果表明，半干旱山坡下坡部分的草种在减少水土流失方面表现更好。在实施恢复策略以控制水土流失时，这项研究有利于草料的选择、分配和管理实践，例如草料收获。结果表明，半干旱山坡下坡部分的草种在减少水土流失方面表现更好。在实施恢复策略以控制水土流失时，这项研究有利于草料的选择、分配和管理实践，例如草料收获。