Effect of ground cover on splash and sheetwash erosion over a steep forested hillslope: A plot-scale study

The contributions and relationships of erosion by splash and overland flow over a steep slope in a Japanese beech forest in plots with different percentages of ground cover were examined. Three erosion plots (2 m wide × 5 m long) with average understory coverage of 1%, 45%, and 94% were installed. Sediment transported by rain splash and by overland flow was sampled separately. For the plots with sparse, moderate, and high understory coverage, the average proportions of splash soil to total soil erosion during the monitoring period were 16%, 32%, and 18%, respectively. A significant correlation between the amount of splash soil and precipitation was found in the plots with 1% and 45% understory coverage, whereas no statistical relationship was identified for the plot with high understory coverage. At the sparse ground cover plot showing the largest sediment movement, the contribution of splash transport decreased with increasing precipitation. The amount of sheetwash erosion was significantly correlated with the amount of splash soil under the condition of sparse ground cover. This relationship was more pronounced during high precipitation events and the rainy season. Splash contribution to the sediment transport was in the range of 0.8%–76.7%, 2.8%–81% and 2.1%–60.8% for plot with high, moderate and low ground cover, respectively. The sparse ground cover showed the largest variation of splash and sheetwash contribution in soil erosion. This variability was due to variation in ground cover and soil surface wetness condition which led to a variation of detachment and non-linear relationship of sheetwash splash.     

工程堆积体陡坡坡面径流水动力学特性

通过野外放水试验,对高速公路沿线典型堆积体陡坡(36°)在模拟径流冲刷条件下的坡面径流水动力学特性进行了研究,结果表明,平均流速与径流深均随流量的增加呈幂函数增加,不同坡面径流状态下(薄层水流和细沟流)流量的指数不同,且各自与室内研究结果有所差异;不同坡段的平均流速随坡长增加呈“S”形曲线变化.堆积体陡坡坡面径流属急流范畴,由过渡流向紊流转变的临界放水流量在20～25 L/min之间.Darcy-Weisbach阻力系数(f)与径流雷诺数(Re)之间存在幂函数正相关关系,与弗罗德数(Fr)之间存在幂函数负相关关系,不同坡段的平均阻力系数与坡长呈双曲线函数关系.     

工程堆积体陡坡坡面土壤侵蚀水动力学过程

工程堆积体产生的新增水土流失严重威胁工程建设区及其附近区域的生态安全。该文采用野外放水冲刷试验的方法,对神木-府谷高速公路沿线典型工程堆积体陡坡坡面土壤侵蚀水动力过程进行了研究,结果表明,1）水流剪切力、水流功率及径流动能对薄层水流侵蚀土壤剥蚀率的影响皆可用线性方程描述,单位水流功率、过水断面单位能量的影响不显著;2）水流剪切力、水流功率、过水断面单位能量对细沟侵蚀土壤剥蚀率的影响皆可用线性方程描述,单位水流功率的影响可用幂函数方程描述,径流动能的影响可用对数线性方程描述;3）水流功率是与土壤剥蚀率关系最好的水动力学参数,是坡面侵蚀的动力根源;4）发生细沟侵蚀的临界水流功率为3 N/(m·s),细沟可蚀性参数为8×10-3 s2/m2。该结果可为工程堆积体陡坡坡面土壤侵蚀模型的建立奠定基础,为生产建设项目区新增水土流失治理提供科学依据。     

Effect of intercropping maize and closely spacedLeucaena hedgerows on soil conservation and maize yield on a steep slope at Ntcheu,Malawi

A six-year soil conservation trial was conducted on a steep slope, 44%, with a subhumid climate, based on very closely spaced (90 cm) hedgerows, using three intraspecific hybrids ofLeucaena leucocephala. Soil loss averaged 2.0 t/ha per year on theLeucaena plots compared with an initial 80 t/ha per year on the unprotected control plot, falling to 27 t/ha per year after the top soil had been eroded. After 6 years, micro terraces of 35 cm high and 81 cm wide had developed on the intercropped plots, with substantially improved soil properties. Maize yield (unfertilized) were maintained at 1.5–2.0 t/ha on the protected plots, compared with a progressive fall from 0.8 to 0.5 t/ha on the sole maize control.     

亚洲热带地区的土壤资源及土地利用

Tropical Asia is a region comprising South and Southeast Asia and under strong influence of the Asian monsoon climate.It is characterized by and extremely high population density and by high land use intensity.Paddy rice cultivation is the most important form of agriculture in the greater aprt of the region.Soil resources of tropical Asia have a specific feature in comparison with tropical Africa and America.Ultisols dominate in uplands,and lowland soils like Inceptisols and Histosols are relatively abundant.The latter point is made clearer if we take the landforms of the region with a vast extent of lowlands into consideration.Geologically,tropical Asia with the Himalayan orogeny and active volcanism exhibits a conspicuous contrast to tropical Africa and America with the dominance of the shield structure.This along with the monsoon climate should have determined the basic features of landforms and soil,and acoordingly all the agricultural and social characteristics of tropical Asia today,Although paddy rice cultivation in the lowland is highly sustainable,upland cultivation in extensive Ultisol areas tends to be handicapped by low fertility and high erodibility of the soil,resulting in low sustainability.Land shortage is compelling people to exploit slopelands in hills and mountains,on the one hand,and thus far unutilized coastal lowlands,on the other,Both of these new reclamations are facing to serious land degradation problems todary.Torpical Asia will continue to be the most densely populated region of the wolrd with ever-increasing population.In order to meet the increasing food demand lowlang rice cultivation should beintensified by the infrastructure development to ease the stresses on slopelands and vulnerable coastal lowlands.At the same time,upland crop production in Ultisol areas should be stabilized and enhanced,providing integrated nutrient management and measures for soil conservation.     

红壤坡地果园不同耕作措施的水土保持效应研究

针对南方广大红壤坡地果园因耕作不当而导致的水土流失,开展了系列研究。通过翔实的观测数据认真分析了不同耕作措施差异,找出了多种措施的优劣,分别是横坡耕作、顺坡耕作、果园清耕和裸露对照,得出了增加植被、改进耕作有明显的保持水土作用,单纯的耕作措施仍不能杜绝水土流失,欲要从根本上控制,还应与其他措施配合的结论。     

确定陡坡细沟侵蚀含沙量的解析方法

该文介绍一种解析方法，由细沟剥蚀率与含沙量关系以及剥蚀率与水流含沙量及沟长的微分物理表达式，推求出了含沙量与沟长关系数学表达式。提出了一种侵蚀细沟含沙量量化计算的新方法。并将用该方法计算得到的两种流量下细沟水流含沙量结果与由试验值进行了比较，结果表明：两者相关密切，得到的R²值均很高，最低为0.81，验证了此解析式的有效性。验证了细沟土壤侵蚀的剥蚀率与水流含沙量的关系式的正确性。     

陕北峁状丘陵区陡坡地杏树栽培研究

通过多年试验研究，提出陡坡地树栽培的品种选择、整形剪枝、土肥管理等配套技术。陡坡地栽培杏树。可明显提高水土保持效果及经济效益，收入是种植马铃薯的６－７倍。