基于2009-2018年径流小区观测数据的武汉市土壤侵蚀因子定量评价

武汉市位于桐柏山大别山国家级水土流失预防区与幕阜山省级水土流失治理区之间，其土壤侵蚀问题对长江中游生态安全具有重要影响。基于2009-2018年武汉市蔡店、磨盘山、西湖流域、燕子山等4个水土保持监测站35个径流小区的观测数据（139组），定量分析了坡度、侵蚀性降水量、土地利用和水土保持措施对土壤侵蚀的影响，并借鉴USLE模型识别土壤侵蚀主导因子。结果表明，裸地小区的平均土壤侵蚀模数最高（2597.57 t km^-2 a^-1），其次是经济林、草地和耕地小区且三者的侵蚀模数相差不大，土壤侵蚀模数与侵蚀性降雨量、坡度之间呈显著二元线性或幂函数关系；与天然植被小区相比，植物篱（草带、茶树、紫穗槐）及石坎梯田措施均显著降低了土壤侵蚀模数，其中植物篱措施的效果更优，且草带植物篱小区的侵蚀模数最低（46.13 t km^-2 a^-1）；3个坡度等级（0-10°、10-20°、20-25°）小区平均侵蚀模数分别为892.07、911.15、2087.60 t km^-2 a^-1，表明坡度超过20°后土壤侵蚀严重加剧；武汉市土壤侵蚀的主导因子为水土保持措施、植被覆盖与管理因子。研究结果可为武汉市水土保持措施合理布设及侵蚀预报模型的完善提供依据，基于径流小区长期观测数据的土壤侵蚀定量研究值得进一步深入。

Quantitative evaluation of soil erosion factors in Wuhan based on observation data of runoff plots during 2009-2018

Wuhan city is located between the National Soil and Water Loss Prevention Area of Dabie Mountain and the Provincial Soil and Water Loss Control Area of Mufu Mountain. The soil erosion issue has an important impact on the ecological security of the middle reaches of the Yangtze River. This study quantitatively analyzed the effects of slope, erosive precipitation, land use, soil and water conservation measures on soil erosion, based on the observation data (139 groups) of 35 runoff plots from four monitoring sites including Caidian, Mopanshan, Xihu, and Yanzishan in Wuhan during 2009-2018. Meanwhile, dominant soil erosion factors were identified using the revised USLE model. The results showed that for the plots with different land use types, the average soil loss of bare land was the highest (2597.57 t km^-2 a^-1), followed by economic forest, grassland, and cultivated plots, and the average soil loss of which were close. There was a significant binary linear or power function relationship between the soil loss, erosive precipitation and slopes. The crop/vegetation types with the highest soil loss reduction rate in granite red soil, yellow brown soil and brown earthl plots of Wuhan City were respectively Chestnut, artificial secondary forest and grassland. Compared with natural vegetation-covered plots, both hedgerows (grass strips, tea plants, amorpha fruticosa) and rock ridge terraces significantly reduced the soil loss, and these soil and water conservation measures had stronger soil erosion control effect under lower erosive precipitation. In addition, the effect of hedgerow measures was better than rock terraces, and soil loss of the grass strip hedgerow plots was the lowest (46.13 t km^-2 a^-1). The average soil loss of the plots with slopes of three ranges (0-10°, 10-20°, 20-25°) were 892.07, 911.15 and 2087.60 t km^-2 a^-1, respectively, indicating that soil erosion rapidly increased with the slope exceeding 20°. The dominant erosion factors were soil and water conservation measure, vegetation cover and management factors. There was a good linear relationship between soil loss and the improved soil erodibility factor K'' in this paper, which showed that K'' had a significant effect in indicating the comprehensive influence of surface cover factors and soil erodibility factors. The results can provide a basis for the reasonable arrangements of soil and water conservation measures and the improvement of erosion model in Wuhan. Furthermore, quantitative assessment of regional soil erosion based on long-term observation data from field runoff plots is worthy of further study.