影响土壤水蚀的环境因子分析

土壤侵蚀是一种复杂的人文和地理过程,受到众多环境因子的影响。综合介绍了影响土壤水蚀的降雨侵蚀力、植被覆盖与水土保持措施、地形、土壤可蚀性因子,并定性分析了各因子对土壤侵蚀的影响,以期促进该项研究工作的深入开展。     

黄土高原典型区降雨植被耦合对侵蚀产沙影响的临界研究

降雨植被耦合对土壤侵蚀的影响是研究地表侵蚀过程的重要内容。根据1954—1986年西峰水土保持科学试验站人工草地和自然草地径流场观测资料,从微观角度分析了降雨植被耦合对土壤侵蚀的影响。研究结果是:当牧草覆盖度<10%时,极端侵蚀模数随着植被覆盖度的增大而增大,这说明要使植被起到有效的抗蚀作用,其覆盖度不应低于10%;当植被覆盖度>10%时,极端侵蚀模数与植被覆盖度呈良好的幂函数关系;如果要使植被抗蚀力起主导作用且达到最优效果,则其覆盖度至少要达到70%。     

小型人为坡面土壤侵蚀、坡面演化与防治对策

我国南方丘陵区土壤侵蚀严重,人类活动对其有重大影响,其中小型人为坡面的土壤侵蚀尤为强烈.根据1990～1996年对苏南孔山地区小型人为坡面土壤侵蚀的观测,土壤侵蚀主要发生在山麓人为开荒、挖土造成的裸露坡面上,土壤侵蚀的季节性变化明显,微沟谷侵蚀、溅蚀与土溜是主要的侵蚀方式.伴随着坡面地貌演化与植被覆盖度的增加,坡面土壤侵蚀趋于停止,人为裸露坡面的侵蚀过程历时6年,早期土壤侵蚀严重.针对侵蚀特征提出了防治小型人为坡面土壤侵蚀的对策.     

闽北山区小流域土壤侵蚀因素特征与防治措施效益研究

土壤侵蚀六大影响因素中，降雨侵蚀力、土壤可蚀性、自然地形(坡度、坡长)对闽北小流域土壤侵蚀的潜在威胁大；闽北植被因素优于其他地区，一些耕作方式增加了土壤侵蚀的发生。针对流域土壤侵蚀影响因素特征采取以保护现有植被为主，重建植被为辅；修建坡地工程和改良耕作方式结合的综合措施，闽北小流域综合治理取得显效益。     

植被恢复背景下土壤侵蚀研究需要加强的内容

植被是调控土壤侵蚀的关键因素,退耕还林(草)工程的有效实施使入黄泥沙锐减,充分证明植被恢复已显著改变了黄土高原的土壤侵蚀环境。但区域侵蚀泥沙的显著减少,仅体现了植被恢复驱动侵蚀泥沙变化的集总效应,无法揭示植被恢复影响土壤侵蚀的过程与动力机制。在黄土高原植被恢复的大背景下,提出了细沟间、细沟、切沟、重力侵蚀需要加强研究的重点内容,明确了新形势下不同侵蚀类型小流域侵蚀泥沙贡献、植被影响土壤侵蚀的参数表征和多时空尺度小流域土壤侵蚀预报模型等方面急需加强的研究内容,旨在揭示植被影响土壤侵蚀的动力学机理,明确植被恢复导致区域侵蚀泥沙锐减的物理机制,确定植被恢复水土保持效应的可持续性,维系区域生态系统服务功能,实现黄河流域生态安全与健康发展。     

黄土高原土壤侵蚀特点与植被对土壤侵蚀影响的研究

黄土高原土壤侵蚀异常强烈,并且大部分地区以水蚀为主。在水蚀区,土壤侵蚀主要由少数几次暴雨所引起。黄土高原的土壤侵蚀情况比较复杂,以各种类型的沟蚀为主,并具有垂直分带性。坡耕地的土壤侵蚀,占总侵蚀量的比重很大。同时,根据在子午岭地区的土壤侵蚀调查,讨论了植被对土壤侵蚀的影响。     

基于GIS的黄土高原不同植被区土壤侵蚀研究

在对黄土高原植被进行分区的基础上,利用地理信息系统技术和景观生态学方法对黄土高原植被区空间数据和土壤侵蚀空间数据进行了空间叠加分析。结果表明,黄土高原被划分为森林植被区、森林草原植被区、温性草原植被区和荒漠半荒漠植被区。在森林植被区,黄土高原土壤侵蚀主要以水蚀为主,轻度以上的侵蚀百分比为41.92%,水蚀土壤侵蚀指数比温性草原植被区和荒漠半荒漠植被区的水蚀土壤侵蚀指数大,为346.90。在森林草原植被区,黄土高原土壤侵蚀主要以水蚀为主,轻度以上的侵蚀百分比为70.45%,水蚀土壤侵蚀指数均比其他植被区的水蚀土壤侵蚀指数大,为449.40,水蚀最为严重。在温性草原植被区,黄土高原土壤侵蚀主要以水-风混合侵蚀为主,风蚀微度-水蚀剧烈的百分比最大,为33.01%,水-风混合侵蚀土壤侵蚀指数均比其他植被区的水-风混合侵蚀土壤侵蚀指数大,为633.45,水-风混合侵蚀最为严重。在荒漠半荒漠植被区,黄土高原土壤侵蚀主要以风蚀为主,轻度以上的侵蚀百分比为99.65%,风蚀土壤侵蚀指数均比其他植被区的风蚀土壤侵蚀指数大,为589.78,风蚀最为严重。黄土高原的土壤侵蚀表现出明显的地带性分异规律。     

基于WEPP模型的水土保持措施因子与侵蚀量关系研究

水土保持措施能够有效减少水土流失,是土壤侵蚀过程中的一个重要影响因子。以北京市延庆县水土保持科技示范园的径流小区观测数据为基础,利用WEPP模型模拟了坡面不同水土保持措施下的侵蚀量,结果表明:(1)植被盖度与侵蚀量呈负相关关系,植被盖度越高侵蚀量越少,当盖度50%时侵蚀量会显著减少,且植被有效盖度的阈值为70%;(2)梯田的土壤侵蚀过程主要发生在田坎处,水平田面几乎没有水土流失,侵蚀量与田坎高成正比,与田面宽成反比。在北方土石山区,水平梯田田坎高度不宜超过2.5 m,田面宽不宜小于5 m;(3)粮—草间作能有效减少土壤侵蚀量,且草带所占比例越大减蚀效益越好。在水土保持为主的坡耕地上适合推广粮:草比为2:4的间作配置模式。研究结果对于北方土石山区的土壤侵蚀研究以及水土保持措施的配置具有一定参考意义。     

蒲河流域退耕前后降水和植被对土壤侵蚀变化的影响

为了定量评价退耕还林还草前后蒲河流域土壤侵蚀变化特征及降水和植被对土壤侵蚀的影响,运用修正后的通用土壤流失方程(RUSLE模型)探讨1990—2019年流域土壤侵蚀变化,结合LMDI模型评估了1990—2000年、2000—2010年、2010—2019年3个时间段植被和降水对流域土壤侵蚀变化的影响。结果表明：30年来,流域侵蚀强度以微度和轻度侵蚀为主,而中度及以上等级的土壤侵蚀面积有逐渐减小的趋势;流域侵蚀情况总体持续向好,植被覆盖度与降雨侵蚀力相互作用驱动了研究区土壤侵蚀的动态发展;2000年以前,降水是影响土壤侵蚀变化的主导因素,随着退耕还林还草工程的实施,植被作用逐渐凸显。蒲河流域的退耕还林还草成效显著,是流域侵蚀防治的有效措施,应在侵蚀较强的流域中上游地区继续加强植被恢复措施。     

花岗岩风化壳的层次特性对土壤侵蚀及其防治措施的影响

花岗岩发育的土壤剖面具有显著的层次结构,各层次的颗粒组成、有机质含量都有很大的差异。不同层次土壤的抗侵蚀性能也因此有很大的差异,从表土层往下逐渐降低,砂土层最低,而到碎屑层又有所提高。随着上层土壤被侵蚀冲刷掉,下层土壤依次出露,土壤侵蚀类型也随之发生变化,依次会发生面蚀——沟蚀——崩岗侵蚀。土壤侵蚀模数与侵蚀强度会逐渐增强,到碎屑层出露时有所降低,土壤侵蚀程度则会不断加深。不同层次出露,土壤侵蚀类型发生变化,因此治理措施也应随之变化：表土层与红土层出露时,主要是提高土壤入渗率,从而减少土壤侵蚀量;砂土层出露时,以减少水流对土壤的直接冲刷作用为主;碎屑层出露时,以植被恢复为主。     

黑土区土壤侵蚀厚度对土地生产力的影响及其评价

为了研究黑土区土壤侵蚀厚度对土地生产力的影响,采用盆栽试验,人为剥离黑土表层0、5、10、15、20、25和30 cm土壤以模拟侵蚀厚度不同的耕层土壤,分析土壤侵蚀厚度对土壤理化性质、大豆生物性状和水分利用效率等指标的影响。并对TOPSIS(technique for order preference by similarity to ideal solution)模型进行改进,用于评价侵蚀厚度不同的土壤的土地生产力。结果表明:土壤全N、碱解N、全P、速效P、有机质含量和土壤田间持水率均随侵蚀厚度的增加而递减,土壤容重随侵蚀厚度的增加而递增。土壤侵蚀厚度对大豆生长有显著影响,随着侵蚀厚度的增加,大豆减产率呈"S型"曲线递增,产量、耗水量呈"Z型"曲线递减,水分利用效率呈指数曲线关系递减。改进的TOPSIS模型对不同侵蚀厚度下土地生产力的评价结果较为理想,计算的土地生产力指数随土壤侵蚀厚度的变化呈"Z型"曲线,与大豆产量的变化趋势相同,且二者呈指数函数关系,决定系数达0.996,均方根误差为0.65。研究结果可为黑土区土壤侵蚀防治提供理论依据。     

Why soil erosion models over-predict small soil losses and under-predict large soil losses

Evaluation of various soil erosion models with large data sets have consistently shown that these models tend to over-predict soil erosion for small measured values, and under-predict soil erosion for larger measured values. This trend appears to be consistent regardless of whether the soil erosion value of interest is for individual storms, annual totals, or average annual soil losses, and regardless of whether the model is empirical or physically based. The hypothesis presented herein is that this phenomenon is not necessarily associated with bias in model predictions as a function of treatment, but rather with limitations in representing the random component of the measured data within treatments (i.e., between replicates) with a deterministic model. A simple example is presented, showing how even a `perfect' deterministic soil erosion model exhibits bias relative to small and large measured erosion rates. The concept is further tested and verified on a set of 3007 measured soil erosion data pairs from storms on natural rainfall and run-off plots using the best possible, unbiased, real-world model, i.e., the physical model represented by replicated plots. The results of this study indicate that the commonly observed bias, in erosion prediction models relative to over-prediction of small and under-prediction of large measured erosion rates on individual data points, is normal and expected if the model is accurately predicting erosion rates as a function of environmental conditions, i.e., treatments.     

区域土壤侵蚀普查方法的初步讨论

区域土壤侵蚀调查制图和动态分析,是国家和省区编制土壤侵蚀宏观规划的数据基础,也是一个重大前沿性研究命题。在综述国内外区域土壤侵蚀调查制图、区域土壤侵蚀因子、土壤侵蚀尺度效应和土壤侵蚀模型等研究现状的基础上,对即将开展的全国土壤侵蚀普查工作提出以下建议：土壤侵蚀普查需要充分利用我国土壤侵蚀模型研究的最新成果,采用模拟计算方法实现对土壤侵蚀强度的定量估算;调查内容应包括区域土壤侵蚀因子、土壤侵蚀类型与强度、水土保持措施、典型区域抽样调查等;对土壤侵蚀尺度效应、区域土壤侵蚀模型应用示范和区域土壤侵蚀数据库建设方法等关键技术展开攻关研究。     

土壤侵蚀/水土保持与气候变化的耦合关系

通过综述土壤侵蚀对碳循环的影响、全球气候变化对土壤侵蚀的影响以及水土保持植被恢复对碳循环与土壤碳素积累的影响,研究土壤侵蚀/水土保持与气候变化的耦合关系。结果表明:因侵蚀造成的土壤碳素损失是巨大的,但土壤侵蚀是碳源还是碳汇过程依然存在争议,焦点集中于因侵蚀造成土壤团聚体解体,暴露在空气中的土壤有机碳的矿化速率的大小;随着全球气温升高以及降雨格局的变化,全球土壤侵蚀强度和范围都在不断增加,但土壤侵蚀对全球气候变化的响应程度依然值得深入研究;水土保持生态恢复主要通过改变下垫面性质来改变土壤有机碳含量、影响土壤CO2释放并促进土壤碳素积累,对抑制大气CO2浓度升高能产生积极影响。尽管土壤侵蚀/水土保持与气候变化的耦合关系方面的研究已取得重大进展,但仍有待于在土壤侵蚀过程中碳素变化模型、土壤侵蚀过程中氮素迁移转化特征以及侵蚀劣地生态恢复过程中土壤碳素积累机制等方面加强研究。     

Simulation of rill erosion in black soil and albic soil during the snowmelt period

Snowmelt-induced rill erosion could bring serious harm for soil quality and agricultural productive conditions of slope farmland in the black soil zone of Northeast China. In this study, we conducted laboratory experiments to investigate the effects of the freeze-thaw (FT) temperature, number of FT cycles, water content, flow rate, and thaw depth on rill morphology and erosion amount in two common soil (black soil and albic soil). The thaw depth obtained the maximum range, which was the primary factor for the width-to-depth ratio of rills in the black soil; whereas, the flow rate obtained the maximum range as the primary factor for rill erosion in black soil and albic soil. The number of FT cycles had a minor effect on rill erosion in the two soils. Under the same conditions, the rill morphology showed a large difference between the two soils, and higher rill erosion occurred in albic soil than black soil. Rill erosion was relatively high in black soil and albic soil when the FT temperature fluctuated around 0°C during freezing-thawing. The water content exhibited a greater effect on rill erosion in black soil than in albic soil. The unthawed frozen layer could promote rill erosion during snowmelt period to some extent. The results could provide some reference for future study snowmelt-induced rill erosion mechanism and preventive measures.     

利用侵蚀模型普查黄土高原土壤侵蚀状况

土壤侵蚀普查对于土地资源保护和自然灾害防治具有重要意义。为了测试抽样方法和土壤侵蚀模型在土壤侵蚀普查中的适用性,该文以陕西吴起县为试点,采用1%均匀抽样方法,调查39个抽样单元的土壤侵蚀影响因子,使用中国侵蚀预报模型CSLE(Chinese soilloss equation)估算土壤侵蚀模数,并与基于遥感数据的水蚀分级分类方法进行比较。两种方法估算的全县平均土壤侵蚀模数分别为4571和5504t/(km2a),但不同分级侵蚀强度的面积和空间分布存在较大差异。抽样方法在土地利用与覆盖、水土保持措施及土壤特性方面获得的信息量大于遥感方法,同时对于区域具有很好的代表性;使用模型估算土壤侵蚀考虑的影响因子与分级方法相比,还包括了土壤可蚀性、坡长因子以及水土保持措施因子等,由此计算的土壤侵蚀模数和强度具有更高的可信度。因此,虽然基于抽样方法和土壤侵蚀模型的土壤侵蚀普查方法也存在一定的问题,但与土壤侵蚀分类分级方法相比具有明显的优越性。     

红壤裸露坡地次降雨土壤侵蚀规律

揭示红壤裸露坡地次降雨土壤侵蚀规律可为红壤坡地水土流失防治和水土保持效益评价提供科学依据。该文基于典型红壤区裸露坡地试验小区134场次降雨气象、水文观测资料,选取雨量、历时和雨强为特征指标,综合采用快速聚类和判别聚类,划分确定出3种雨型:A雨型(高频次、短历时、小雨量、大雨强),B雨型(中频次、中历时、中雨量、中雨强)和C雨型(低频次、长历时、大雨量、小雨强)。其中,A雨型是造成红壤裸露坡地土壤侵蚀的主要降雨类型。通过Pearson相关分析和Mann-Kendall检验表明,红壤裸露坡地土壤侵蚀主要受雨强和雨量共同影响,雨强的指标中以最大30 min雨强与其关系最为密切,是导致土壤侵蚀变化的直接因素,雨量则通过改变雨强产生一定的间接影响。土壤侵蚀强度随最大30 min雨强增大过程中,在15 mm/h处存在明显转折,最大30 min雨强小于该值前,侵蚀强度呈缓慢增大,大于该值后,侵蚀强度快速增大。土壤侵蚀与雨量整体呈同步增大,但不同雨型的单位雨量侵蚀能力表现为A雨型B雨型C雨型。在排除前期降雨影响的前提下,利用数理统计方法建立了南方红壤裸露坡地次降雨土壤侵蚀强度与雨量和最大30 min雨强的幂函数统计关系,用于3类雨型下的侵蚀预报时整体精度较好,且更适于短历时暴雨。以上研究将为深入揭示红壤坡地土壤侵蚀规律和构建预报模型提供有益参考。     

Impacts of soil erosion on organic carbon and nutrient dynamics in an alpine grassland soil

The impact of soil erosion on the nutrient dynamics in alpine grassland soils is still an essential problem. Selecting a grass-covered hillslope in eastern Tibet Plateau, the cesium-137 (¹³⁷Cs) technique was used to determine the impacts of soil erosion on soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and total potassium (TK). The ¹³⁷Cs data revealed that there were distinct soil redistribution patterns in different hillslope positions because of the influences of slope runoff, plant coverage and grazing activity. For the upper slope, soil erosion first decreased downward, followed by soil deposition in its lower part. In contrast, for middle and toe slopes, there was an increasing soil erosion along a downslope transect. Across the lower slope, soil erosion showed an irregular variation. Influenced by the selective transport of water erosion, SOC, TN and TP storage decreased with increasing soil erosion in upper, middle and toe slopes. In contrast, SOC, TN and TP storage varied little with soil erosion in the lower slope. On the whole hillslope, TK storage also varied little with soil erosion due to the large amount of potassium elements derived from soil parent materials. Particularly noteworthy was the greatest storage of SOC, TN and TP in the lower slope where most obvious net soil erosion occurred, which is closely related to the humus accumulation combined with gravel separation as well as weathering and pedogenesis of parent rocks induced by soil freeze-thaw.     

Evaluating the impact of soil management on soil loss in olive orchards

Abstract. The effects of soil management on soil losses from olive plantations in southern Spain were evaluated using the Revised Universal Soil Loss Equation (RUSLE), a review of published experiments, and preliminary results of an on-going field trial. Experimental data were used to parameterize the RUSLE for olive orchards under various soil management regimes. The predictions agreed qualitatively with the data available, and the model provided a simple way to assess the effects of soil management on erosion. Our results showed that no-tillage caused the greatest soil loss, while cover crops showed the least. Tillage and planting following contours proved only partially effective and did not reduce soil erosion as much as protective crops. One scenario studied suggests that, on slight to moderate slopes, land transformed from row crops to olive orchards may remain below the maximum tolerable soil erosion limit, if a cover crop is included between the trees. A scenario for marginal olive orchards located on steep slopes suggests that effective erosion control could only be achieved with a cover crop system that would have the side-effect of reducing the yield of rain-fed olives. Quantifying the effects of soil management on soil erosion in olive orchards is uncertain because very few experimental results are available. Further research that monitors soil loss in carefully selected long-term experiments at different scales and follows the changes in key soil parameters is urgently required to develop effective erosion control policies.     

Allowable soil erosion rates in Georgia

A procedure was proposed for the determination of the maximum allowable soil disturbance in Georgia in order to develop a strategy of soil conservation and restoration. The allowable soil losses were calculated within the risk limits of 0.01 < r < 0.1. The lower and upper limits of the allowable soil loss were determined for the soils of different thicknesses. To compare the rates of the soil erosion, one uses the erosion index: the ratio between the actual erosion rate and its maximum allowable value. The actual erosion rate is determined from erosion equations, in which the integrated parameters of the soil loss tolerance include the permissible flow velocity and data on the climatic and soil conditions. From the estimated allowable soil erosion rates, criteria of decision making can be formulated for substantiating the strategy of soil conservation or restoration.