[Characteristics of soil anti-scouribility in gully head wall of grass-covering on the gullied Loess Plateau, Northwest China].

Vegetation restoration in the Chinese Loess Plateau has significantly changed soil erosion process of gully head wall. In order to investigate the characteristics and controlling factors of soil anti-scour properties of gully head covered by grasses, we carried out indoor undamaged soil trench scouring tests. By using barren gully head as the control, the physical and chemical properties and anti-scouring characteristics of soil in different soil layers (0-10, 10-20, 20-40, 40-60, 60-80, 80-100 cm) of the vertical wall of gully with grass cover were analyzed. The results showed that water-stable aggregate content and cohesion in barren and grass-covering gully head decreased with soil depth. Soil organic matter content and soil anti-scouribility coefficient in barren gully head decreased with soil depth, while the two indicators for gully head covered by grass increased firstly and then decreased with soil depth, with the maximum value (24.30 g·kg-1 and 58.86 L·g-1) in 10-20 cm soil layer. Meanwhile, the soil anti-scouring coefficient in each soil layer of grass-covering gully head was 1.7-9.3 times of that in soil layer of barren gully head. Soil organic matter content, water-stable aggregate content, cohesion and root length density all presented significantly positive correlation with soil anti-scouribility, among which soil organic matter content had the highest coefficient (r=0.98). Results of this study might provide basic data for the study of headcut erosion mechanism in Loess Plateau gully region, and scientific basis for effective control of soil and water loss in this region.黄土高原植被恢复使沟头立璧土壤侵蚀过程发生显著变化。为明确黄土高塬沟壑区草地沟头立壁土壤抗冲性特征及其影响因素,以裸地为对照,利用室内原状土槽冲刷试验研究了草地沟头立壁0～1 m不同土层(0～10、10～20、20～40、40～60、60～80、80～100 cm)土壤理化性质和抗冲性特征。结果表明: 草地和裸地沟头土壤水稳性团聚体含量和粘聚力随土层加深均呈减小趋势。裸地沟头土壤有机质含量、土壤抗冲系数随土层深度的增加呈减小趋势,而草地沟头土壤有机质含量、土壤抗冲系数随土层加深先增加后减小,且均在10～20 cm土层达到最大值(24.30 g·kg-1和58.86 L·g-1),草地各土层土壤抗冲系数是裸地的1.7～9.3倍。沟头土壤抗冲性与土壤有机质含量、水稳性团聚体含量、黏聚力和植物根长密度呈极显著相关,其中与土壤有机质含量(r=0.98)的关系最密切。该研究可为黄土高塬沟壑区沟头溯源侵蚀机理的研究提供基础数据,并为有效防治该区域水土流失提供科学依据。.