黄土坡面土壤侵蚀过程试验研究

采用人工模拟降雨的方法对黄土坡面土壤侵蚀过程进行了试验研究,取得了如下结果:①坡面土壤侵蚀随降雨过程的变化可用幂函数相关方程进行描述,15 m in和35 m in是土壤侵蚀强度随降雨过程变化的转折点;②雨强对坡面土壤侵蚀的影响可用幂函数相关方程进行描述,随着坡度的增大,土壤侵蚀强度随雨强的增大而增加的趋势更明显;③坡度对土壤侵蚀的影响可用抛物线相关方程进行描述,土壤侵蚀强度变化的临界坡度在25°附近;④坡长对土壤侵蚀的影响大体可用幂函数相关方程进行描述,但坡长对土壤侵蚀强度的影响比较复杂,随雨强大小的变化而表现为不同的形式;⑤坡度、坡长及雨强对坡面土壤侵蚀的综合影响可用多元线性相关方程进行描述,雨强对土壤侵蚀强度的影响远大于坡长及坡度因子,且坡度与土壤侵蚀强度的关系较坡长为密切。

黄土裸坡土壤侵蚀过程研究

黄土地区的土壤侵蚀严重地影响了当地和黄河下游地区的可持续发展,研究黄土地区的土壤侵蚀对于该地区的水土保持工作具有重要意义。采用人工模拟降雨试验的方法对黄土裸坡土壤侵蚀过程进行了研究,取得了如下结果:(1)不同雨强条件下,坡地土壤侵蚀随降雨过程的变化相似,可用幂函数相关方程进行描述,侵蚀强度变化的转变点在降雨开始后的10～15min之间;(2)不同雨强条件下,坡度对土壤侵蚀的影响相近且可用抛物线相关方程进行描述,侵蚀强度变化的临界坡度在25～30°间;(3)不同雨强条件下,坡地土壤侵蚀总量随坡长的变化可用幂函数相关方程进行描述,但坡长对侵蚀模数的影响比较复杂,表现为不同的形式;(4)不同坡度条件下,降雨强度对土壤侵蚀的影响相似且均可用线性相关方程进行描述,随着坡度的增大,土壤侵蚀随雨强增大而增加的越明显;(5)裸坡次降雨侵蚀经验模型为多元幂函数统计方程,裸坡条件下降雨强度对土壤侵蚀的影响最大,坡长与坡度的影响基本大体一致。研究结果表明,采取不同措施增加地面覆盖、停止陡坡耕种、截断坡地径流是治理黄土地区水土流失的有效途径。

黄土坡面下坡位土壤侵蚀过程的模拟试验

在中国科学院水利部水土保持研究所,采用2个不同坡长小区室内模拟降雨试验方法,对黄土坡面下坡位侵蚀过程进行研究。结果表明:1)坡面下坡位侵蚀模数随降雨过程、降雨强度及坡度的变化均具有大小交错,上下波动的特征,侵蚀模数随降雨过程的变化总体呈先上升后趋于稳定的态势,随降雨强度的增大而增加,随坡度的增大而先增大后减小,再增大再减小;2)坡面上、下坡位侵蚀模数随降雨过程、坡度及降雨强度的变化均具有明显差异,下坡位明显不如上坡位;3)坡面上坡位汇流和下坡位产流与坡面上坡位输沙对坡面下坡位侵蚀模数的影响可用二元线性方程很好地描述,前者的贡献率为47.8%,后者为20.4%;只通过观测分析小区平均侵蚀特征得出的坡面侵蚀过程,掩盖了坡面下坡位的真实侵蚀过程,采取水土保持措施减少坡面上坡位汇流及增加降雨就地入渗,可以有效地治理坡面下坡位的水土流失。

土壤侵蚀过程数理模型的研究现状

对土壤侵蚀数学模型的研究可追溯到上个世纪,但具有一定理论基础和实用价值模型的出现也只有几十年的历史。随着科学技术的进步,特别是电子计算机技术的迅猛发展,为数学模拟土壤侵蚀过程提供了可能性。迄今为止,土壤侵蚀过程的数学模型可分为四种类型,

“中国主要水蚀区土壤侵蚀过程与调控研究”列入国家“973”计划

在参与“中国水土流失与生态安全科学综合考察”的有关院士专家的建议和努力下，“中国主要水蚀区土壤侵蚀过程与调控研究”正式列入国家“973”计划。

草地植被冠层与根系对黄土坡面侵蚀过程的影响

草地植被能有效控制坡面侵蚀,然而不同草地植被类型及其冠层与根系对坡面侵蚀过程的调控作用尚缺乏系统研究。采用人工模拟降雨方法,定量研究了不同雨强下苜蓿与黑麦草冠层与根系对黄土坡面侵蚀过程、径流侵蚀动力及土壤抗侵蚀能力特征的影响。结果表明:与裸坡相比,苜蓿与黑麦草的平均减流效益分别为17.65%和9.80%,减沙效益分别为63.86%和69.88%。不同雨强下两种草被根系减流减沙的平均相对贡献均高于冠层,且根系减沙的相对贡献随雨强的增加而增大。草地植被主要通过削减坡面径流流速和增加坡面阻力的方式实现对降雨径流侵蚀动力的调控,草被根系对坡面径流的减速作用略大于冠层,但其增阻作用却明显小于冠层。黑麦草对坡面径流的减速增阻效益高于相同部位的苜蓿。坡面土壤侵蚀率与水流切应力的关系可用幂函数y=αx^(β)较好地拟合。幂函数系数α解释为单位水流切应力所引起的土壤侵蚀模数,可作为反映土壤抗侵蚀能力的指标。草被根系作用下的幂函数系数减幅远高于冠层,反映了其增强土壤抗侵蚀能力作用明显高于冠层,这主要源于草被根系结构对表层土壤性质的改善。须根系黑麦草强化土壤抗侵蚀能力优于直根系苜蓿。本研究揭示了草地植被调控坡面侵蚀过程是通过地上冠层与根系的共同作用达到同时调控侵蚀动力和土壤抗侵蚀能力实现的,草被根系对坡面侵蚀控制起主导作用,且以须根系草被对黄土坡面侵蚀的调控效果最佳。上述结果可为草地侵蚀过程研究及黄土高原草被建设与管理提供科学依据。

应用于土壤变化的坡面侵蚀过程模拟

借鉴国内外土壤侵蚀建模的经验与技术，针对我国干旱地区的实际情况，应用微机技术，建立了坡耕地土壤侵蚀过程数学模型ＳＬＥＭＳＥＰ，并在晋西北砖窑沟试验区得到了验证。模拟过程以天为步长，可预报不同耕作措施条件下，基于日降水量的坡面土壤侵蚀量，定量评价人类活动对土壤侵蚀过程的影响，为水土保持的决策和具体措施的制定提供依据。ＳＬＥＭＳＥＰ模型可进行长期模拟，应用于土壤变化和可持续利用的研究。

全球变化与陆地生态系统土壤侵蚀网络:一个多方参与的研究计划

土壤侵蚀是土地持续利用与管理的一个重大威胁,是人为土地退化的主要形式。奥德曼等人(1991)认为全世界大约有六分之一的可用地已遭风蚀或水蚀。土壤侵蚀还能造成异地环境问题,诸如增加空气中尘埃(Stetler等人1994;EPA1994),促使沉积物向河流和湖泊中的迁移(Robinson 1979),以及水库淤塞(Tagwira 1992)。全球变化会使目前状况更恶化。

生物结皮土壤-水文-侵蚀效应研究进展

生物土壤结皮(简称生物结皮)是由隐花植物、微小生物和土壤表层颗粒胶结形成的一种特殊复合体,广泛分布于各类气候和生境条件。作为生态系统的重要组分,生物结皮在不同生物气候区土壤的生态过程、水文过程、生物过程、地球化学循环过程以及生态修复过程中发挥着重要作用。从生物结皮影响土壤物理、化学、生物学性质以及土壤水文与侵蚀过程等方面对其生态功能进行总结和概述,在此基础上,从研究区域和时空尺度、多过程耦合机制、生物结皮影响氮循环的过程及其对氮沉降的响应机制、生物结皮与维管植物空间分布及互动关系等方面,展望了该领域有待深化的问题及今后的发展方向,以期促进我国生物结皮相关研究工作,加深对生物结皮生态功能及地表过程的认识。

不同近地表土壤水文条件下雨滴打击对黑土坡面养分流失的影响

目前,土壤水分饱和和壤中流条件下,雨滴打击对养分流失的影响尚不清楚。通过3个近地表土壤水文条件(自由入渗、土壤水分饱和与壤中流)下,土槽上方架设与不架设尼龙纱网模拟降雨对比试验,研究雨滴打击对黑土坡面侵蚀过程及NO3-N、NH4-N与PO4-P随径流和侵蚀泥沙迁移的影响。结果表明,纱网覆盖消除雨滴打击后坡面侵蚀量和泥沙浓度分别减少59.4%—71.6%和57.3%—73.0%,不同水文条件下减少量的排序为:自由入渗>壤中流>土壤水分饱和。消除雨滴打击后养分随径流流失的减少仅在自由入渗条件下体现较明显,该水文条件下NO3-N、NH4-N与PO4-P流失分别减少33.3%、23.1%和40.7%;3种水文条件下,消除雨滴打击均明显减少养分随泥沙的流失,其中自由入渗条件下减少效果最明显,该水文条件下,NO3-N和NH4-N流失分别减少20.9%—54.9%和25.0%—62.3%,而PO4-P流失减少在74.6%以上。雨滴打击增大了NO3-N的淋失,但对NH4-N与PO4-P的淋失几乎无影响。消除雨滴打击后,自由入渗条件下养分的等效径流迁移深度减少26.7%—42.6%,而土壤水分饱和与壤中流条件下基本无变化。以上研究结果为有效防治坡面土壤侵蚀和农业非点源污染提供科学理论依据,尤其是在壤中流出现的地方。

土壤肥力发生发展及其培肥途径

本文简述了国内外土壤学界对土壤肥力及其发生发展、培肥途径的认识和研究的进程与现状,认为人类生产实践活动是影响土壤肥力变化的重要因素。根据作者多年来从事“两粮一肥”耕作制研究的实践,提出因地制宜,用养结合,改革耕作制度是加速培育土壤肥力的一条重要途径。

中国水土流失基础研究的机遇与挑战

水土流失是制约人类生存和社会可持续发展的重大环境问题,是我国各种生态问题的集中反映,对粮食安全和生态安全造成了严重威胁。国家973项目"中国主要水蚀区土壤侵蚀过程与调控研究"以我国东北黑土漫岗区、西北黄土高原区、南方红壤丘陵区、西南紫色土山丘区4个水蚀区为重点,以土壤侵蚀过程为研究对象,拟解决主要水蚀区土壤侵蚀的发生发展过程与驱动机制、复杂环境下土壤侵蚀模型构建的理论与方法、水土流失与水土保持环境效应评价理论与调控机理等三个关键科学问题。研究水土流失发生发展过程与驱动机制,指导水土保持措施配置与战略规划;阐明流域产沙和水沙运移规律,减少江河洪涝灾害、维系大江大河和大湖安全;构建多尺度土壤侵蚀预报模型,预测发展趋势,指导水土保持规划;建立水土流失与水土保持的环境效应评价理论,为生态建设和制定中国水土保持宏观战略对策提供科学依据。

浅谈人口行为与资源、环境之关系

众所周知,人口、资源、环境是当今全球性三大问题,而人口行为却是引起这三大问题的主要根源之一,全球性的资源衰枯与环境恶化都与人口行为有着极为密切的关系。本文就人口行为与资源、环境之关系作了初步探讨,以土壤侵蚀问题为例,建立了定量分析人口行为对水土流失影响的数学模型,从而从一个侧面揭示了人口、资源、环境之间对立统一的关系。一,人口与资源、环境的统一人口行为的存在,一直可以追溯到人类产生的历史时期,距今已长达几百万年。

Rainfall and Tillage Impacts on Soil Erosion of Sloping Cropland with Subtropical Monsoon Climate- A Case Study in Hilly Purple Soil area, China

Under global warming, storm events tend to intensify, particularly in monsoon-affected regions. As an important agricultural area in China, the purple soil region in the Sichuan Basin, where it has a prevailing monsoon climate, is threatened by serious soil erosion. Tillage operations alter runoff and soil erosion processes on croplands by changing the physical properties of the soil surface. To clarify the relationship between tillage and soil erosion in the purple soil region, three different tillage practices in this region were investigated at the plot scale over 4 years： bare land with minimum tillage （BL）, conventional tillage （CT） and seasonal no-tillage ridges （SNTR） which was initially designed to prevent soil erosion by contoured ridges and no-tillage techniques. The results showed that although there were no significant differences in the surface runoff and soil erosion among the three oractices, BL caused relatively high surface runoff and soil erosion, followed by CT and SNTR. Classification and comparison of the rainfall events based on cluster analysis （CA） verified that the surface runoff was not significantly different between most intensive event and long intensive events but was significantly different between most intensive and short and medium-duration events. Only the rainfall events with the highest rainfall intensity could trigger serious soil erosion, up to 1000 kg ha^-1 in the region. Further detailed investigations on the effects of tillage operations on the soil erosion in a subtropical region with a monsoon climate are needed to provide a basis for modeling catchments and designing better management practices.

Tillage Pedogenesis of Purple Soils in Southwestern China

Land cultivation and tillage process, and their consequent impacts on soil erosion, have been criticized as the main cause of degradation of land or soil quality. However, purple soils, classified as Regosols in FAO Taxonomy or Entisols in USDA Taxonomy, are formed from purple rocks of the Trias- Cretaceous system, have been developed or at least accelerated the development due to continual tillage operation, especially digging and ridging. The present study took micromorphological investigation on the sedimentary rocks and the soils under different operations of tillage. Results show that the purple rock of Feixiangguan Formation of the Trias system （Tlf） is the easiest to physical weathering and the most fertile soil material enriched in nutrients, and it has been, therefore, mostly cultivated and intensively tilled around the year. It has the fastest soil formation rate. Soil formation rate in the cropland with conventional tillage is higher than that in the forestiand and the grassland. It implies that the artificial brokenness and tillage disturbance play a great role in physical weathering and initiating soil formation processes.

Spatio-temporal Variation of Wind Erosion in Inner Mongolia of China Between 2001 and 2010

Using Geographic Information System(GIS), based on wind speed, precipitation, topographic, soil, vegetation coverage and land use data of Inner Mongolia between 2001 and 2010, we applied the revised wind erosion equation(RWEQ) model to simulate wind erosion intensity. The results showed that an area of approximately 47.8 × 10~4 km^2 experienced wind erosion in 2010, 23.2% of this erosion could be rated as severe, and 46.0% as moderate. Both the area and the intensity of wind erosion had decreased from 2001 to 2010, the wind erosion area reduced 10.1%, and wind erosion intensity decreased by 29.4%. Precipitation, wind speed, population size and urbanization in rural areas, and gross domestic product of primary industry(GDP1) were the main factors influencing wind erosion. Overall, these factors accounted for 88.8% of the wind erosion. These results indicated that the decrease in wind erosion over the past decade related to the increase in precipitation and the decrease in the number of windy days, while modest urban development and optimization of the economic structure might partially reduced the level of ecological pressure, highlighting the importance of human activities in controlling wind erosion.

Effects of Shrub on Runoff and Soil Loss at Loess Slopes Under Simulated Rainfall

Improved understanding of the effect of shrub cover on soil erosion process will provide valuable information for soil and water conservation programs.Laboratory rainfall simulations were conducted to determine the effects of shrubs on runoff and soil erosion and to ascertain the relationship between the rate of soil loss and the runoff hydrodynamic characteristics.In these simulations a 20° slope was subjected to rainfall intensities of 45,87,and 127 mm/h.The average runoff rates ranged from 0.51 to 1.26 mm/min for bare soil plots and 0.15 to 0.96 mm/min for shrub plots.Average soil loss rates varied from 44.19 to 114.61 g/(min·m^2) for bare soil plots and from 5.61 to 84.58 g/(min·m^2) for shrub plots.There was a positive correlation between runoff and soil loss for the bare soil plots,and soil loss increased with increased runoff for shrub plots only when rainfall intensity is 127 mm/h.Runoff and soil erosion processes were strongly influenced by soil surface conditions because of the formation of erosion pits and rills.The unit stream power was the optimal hydrodynamic parameter to characterize the soil erosion mechanisms.The soil loss rate increased linearly with the unit stream power on both shrub and bare soil plots.Critical unit stream power values were 0.004 m/s for bare soil plots and 0.017 m/s for shrub plots.

Impact of Land-Use Practices on Sediment Yield in the Dhrabi Watershed of Pakistan

Soil erosion by water is one of the most important land degradation processes in the sloping rainfed lands in Pakistan. A study was conducted in the Dhrabi watershed of Pakistan to evaluate sediment yield associated with rainfall-runoff under various land-use practices. Five sub-catchments with sizes varying from 1.5 to 350 ha were selected for measurement of rainfall, runoff and sediment yield. Soil conservation techniques were also introduced to reduce the soil erosion. All runoff events occurred in the summer especially during monsoon season （July-September）. Sediment yield of two small gully catchments ranged from 4.79 to 8.34 t/ha/yr in 2009, a relatively dry year. In 2010, the annual sediment yield was 8.15 to 12.31 t/ha. Terraced catchment with arable crops produced annual 4.1 t/ha of sediment as compared to 12.31 t/ha by the adjacent gully catchment showing high potential of terraces in reducing erosion. Runoff coefficients calculated for these catchments vary from 0.09 to 0.75. The macro and micro nutrients present in the sediment indicate that these nutrients are being depleted due to soil erosion.

A Review on Rill Erosion Process and Its Influencing Factors

Rills are frequently observed on slope farmlands and rill erosion significantly contributes to sediment yields. This paper focuses on reviewing the various factors affecting rill erosion processes and the threshold conditions of rill initiation. Six factors, including rainfall, runoff, soil, topography, vegetation and tillage system, are discussed. Rill initiation and network are explored. Runoff erosivity and soil erodibility are recognized as two direct factors affecting rill erosion and other types of factors may have indirect influences on rill erosion through increasing or decreasing the effects of the direct factors. Certain conditions are necessary for rill initiation and the critical conditions are different with different factors. Future studies should be focused on 1) the dynamic changes of rill networks; 2) the combined effect of multiple factors; and 3) the relationships of threshold values with other related factors.

Uncertainty Assessment of Soil Erosion Model Using Particle Filtering

Recent advances in computer with geographic information system(GIS) technologies have allowed modelers to develop physics-based models for modeling soil erosion processes in time and space.However, it has been widely recognized that the effect of uncertainties on model predictions may be more significant when modelers apply such models for their own modeling purposes.Sources of uncertainty involved in modeling include data, model structural, and parameter uncertainty.To deal with the uncertain parameters of a catchment-scale soil erosion model(CSEM) and assess simulation uncertainties in soil erosion, particle filtering modeling(PF) is introduced in the CSEM.The proposed method, CSEM-PF, estimates parameters of non-linear and non-Gaussian systems, such as a physics-based soil erosion model by assimilating observation data such as discharge and sediment discharge sequences at outlets.PF provides timevarying feasible parameter sets as well as uncertainty bounds of outputs while traditional automatic calibration techniques result in a time-invariant global optimal parameter set.CSEM-PF was applied to a small mountainous catchment of the Yongdamdam in Korea for soil erosion modeling and uncertainty assessment for three historical typhoon events.Finally, the most optimal parameter sets and uncertainty bounds of simulation of both discharge and sediment discharge at each time step of the study events are provided.