土壤侵蚀日发布系统

土壤侵蚀发布系统作为定量研究土壤侵蚀过程的重要工具,一直是土壤侵蚀学科的前沿领域,其对于估算土壤流失速度、评估水土保持措施效益具有重要的科学意义。然而,现有土壤侵蚀发布系统多仅依靠一年内降雨事件或利用多年平均降雨数据进行潜在土壤侵蚀程度估算,无法对一次平均水平的土壤侵蚀事件进行定量描述,更无法回答土壤侵蚀在何时何地发生,侵蚀动态如何变化,以及降雨、地形、土壤、作物管理方式和极端事件的时空变化对土壤侵蚀的影响。作为土壤侵蚀发布系统领域最新研究进展的土壤侵蚀日发布系统DEP(Daily Erosion Project),解决了以往土壤侵蚀发布系统中出现的上述问题。DEP基于侵蚀模型、地理信息、土地利用、植被变化等信息,逐日模拟降雨、径流、剥离、土壤流失等定量指标,结合第二代气象雷达云图生成土壤侵蚀分布图,实现以日为步长的土壤侵蚀发布,成为首个土壤侵蚀日发布系统,已在美国成功应用。本文详细介绍了土壤侵蚀日发布系统,并对实例进行了分析,探讨了该系统在我国土壤侵蚀发布研究与应用中的前景。

Impacts of horizontal resolution and downscaling on the USLE LS factor for different terrains

Slope length and slope steepness are critical topographic factors(L and S)in the Universal Soil Loss Equation(USLE)and Chinese Soil Loss Equation(CSLE)for soil erosion modelling.Both slope length and slope gradient are potentially sensitive to spatial resolution when calculated in a GIS framework.The resolution effect on the LS factor and approaches suitable for improving the LS factor at a coarse resolution have not been well identified.To address this problem,the LS factor at 5-m and 30-m resolution in twenty-four watersheds with various terrains was estimated.And a downscale model based on matching of the lower resolution LS cumulative frequency curves to a higher resolution("Histogram Matching"method)was tested for its potential to improve LS factor estimation accuracy.In the larger relief mountainous area,compared to 5-m resolution,the 30-m resolution generated LS was generally overestimated by more than 20%and in lower relief areas underestimated by more than 15%.This bias is less than 10%in medium relief areas.The downscale model improved LS factor estimates compared to the 30-m resolution estimate by more than 10%when comparing frequency distribution curves and more than 20%in mean values in larger relief areas.The downscale model worked well in all regions except for the low relief areas,which intuitively are the low soil erosion potential areas.The results of this research help quantify the uncertainty in soil erosion estimates and may ultimately help to improve the assessment of soil erosion through its impact on LS factor estimates,especially at regional and global scales.

Unpaved road erosion after heavy storms in mountain areas of northern China

More frequent extreme rainfall events associated with global climate change cause greater challenges for soil conservation.Severe erosion occurs on many unpaved roads since these structures create important water flow paths during heavy storms.The present research aimed to investigate the intensity and influencing factors of unpaved road erosion under varied land use and management conditions(sloping cropland,terraced cropland,forest&grass).The erosion occurred in the watersheds contributing runoff water to roads after the greatest rainfall event recorded in the mountain area of northern China caused by Typhon Lekima.The research was conducted in an agricultural-forest-dominated watershed based on field investigation and UAV-based image analysis.A road erosion level classification standard was given according to the occurrence of rills,ephemeral gullies,and gullies.Significant erosion happened on 67% of the unpaved roads;42% of them suffered moderate to severe erosion in which ephemeral gullies or gullies developed.The average erosion amount from these roads was 2280.75 t ha-1 and was significantly influenced by the watershed land use type and management.The dominant factor governing unpaved road erosion associated with terraced cropland was vegetation coverage on roads.Drainage area was the most important factor for road erosion in sloping cropland and forest&grass land,and road gradient was also a critical factor.Terraces,and forest&grass in drainage areas significantly reduced unpaved road erosion by 85%and,47%,respectively,compared to sloping cropland.More integrated measures should be used to prevent unpaved road erosion.The results of this research can be applied to road protection against erosion in heavy storms.

Guest editorial-soil erosion assessment, tools and data: A special issue from the Global Symposium on soil Erosion 2019

This special issue on soil erosion assessment,tools and data creation,consolidation and harmonization presents advances in soil erosion research with a focus on new tools that are being used to assess soil erosion rates.This publication includes eleven selected contributions presented at the Global Symposium on Soil Erosion(GSER,15-17 May 2019,Rome,Italy)dealing with erosion indicators'improvement,the use of remote sensing,nuclear techniques and geochemical fingerprinting as promising methods to assess soil losses,management practices that reduce soil erosion in vineyards and olive groves plantations and their modelling,and national and regional erosion assessments.

In Memoriam:Dr.John M.Laflen

The soil erosion research and soil and water conservation global community lost a treasured member on November 20,2020,when Dr.John Matthew Laflen(Fig.1)died.Always one with a friendly welcoming smile,John had hundreds of friends,both personally and professionally throughout the world.This article includes many of his professional and scientific contributions,and impacts from his research and outreach activities.