Weathering of Pisha-Sandstones in the Wind-Water Erosion Crisscross Region on the Loess Plateau

Two types of pisha-sandstones of purple sandstones and gray sandstones,widely distributing in the wind-water erosion crisscross region of China,were selected and used in laboratory experiments for a better understanding of the drying-wetting-freezing weathering process resulting from the apportionment of water or salt solution to rock samples.Weathering experiments were carried out under the conditions of environment control(including temperature,moisture and salt solution).All rock samples were frequently subjected to 140 drying-wetting-freezing cycles.The influences of weathering process were evaluated.It was found that the different treatments of moisture and salt solution applications could affect the nature of the weathering products resulting from drying-wetting-freezing.It was also observed that salt solution could effectively alleviate the weathering of pisha-sandstones.Although not all the observations could be explained,it was apparent that simulated environmental factors had both direct and indirect effects on the weathering of rocks.

Relationship Between Watershed Landscape Pattern Change and Runoff-Sediment in Wind-Water Erosion Crisscross Region

This paper selected the typical wind-water erosion crisscross region Xiliugou watershed for research to reveal the impact of the landscape pattern change of the underlying surface in wind-water erosion crisscross region where soil erosion is most serious on rainfall and runoff as well as erosion and sediment.Based on the Landsat TM image data and measured data of runoff-sediment in that watershed,the paper analyzed the characteristics of watershed landscape pattern change and runoff-sediment and explored the relationship between landscape index and runoff-sediment yield by means of GIS and Fragstats.The results were included as follows.(1)Grassland was the dominant landscape.In terms of the number of patches and area change rate,from 1985 to 2010,cultivated land,forest land and construction land were most stable,followed by unused land.Unused land,grassland and cultivated land experienced the most dramatic conversion and maximally affected by human activities.(2)The inter-annual difference between annual runoff and annual sediment load was significant.Compared with the annual sediment load,the trend of decreasing runoff was more obvious.The correlation coefficient of runoff-sediment was 0.67,representing a significant correlation.(3)There was a significant correlation between the landscape index and runoff-sediment.The runoff was negatively correlated with the largest patch index,patch cohesion index,aggregation index and contagion index,but positively correlated with landscape morphology index and landscape division index.And the sediment was negatively correlated with the contagion index,aggregation index and plaque cohesion index,but positively correlated with other landscape indexes.The results indicate that with the increase of the largest patch index,patch cohesion index and aggregation index,the rainfall infiltration capacity increase obviously and the soil erosion reduce significantly.Therefore,increasing the largest patch index,patch cohesion and aggregation index of the watershed landscape can enhance the function of water storage and soil conservation as well as ecological optimization in the windwater erosion crisscross region.The results can provide theoretical support for the ecological environment construction and comprehensive utilization of water and soil resources.

Influence of Vegetation on Runoff and Sediment in Wind-water Erosion Crisscross Region in the Upper Yellow River of China

All characteristics of vegetation,runoff and sediment from 1960 to 2010 in the Xiliu Gully Watershed,which is a representative watershed in wind-water erosion crisscross region in the upper reaches of the Yellow River of China,have been analyzed in this study.Based on the remote sensing image data,and used multi-spectral interpretation method,the characteristics of vegetation variation in the Xiliu Gully Watershed have been analyzed.And the rules of precipitation,runoff and sediment's changes have been illuminated by using mathematical statistics method.What′s more,the influence mechanism of vegetation on runoff and sediment has been discussed by using the data obtained from artificial rainfall simulation test.The results showed that the main vegetation type was given priority to low coverage,and the area of the low vegetation coverage type was reducing year by year.On the country,the area of the high vegetation coverage type was gradually increasing.In a word,vegetation conditions had got better improved since 2000 when the watershed management project started.The average annual precipitation of the river basin also got slightly increase in 2000–2010.The average annual runoff reduced by 37.5%,and the average annual sediment reduced by 73.9% in the same period.The results of artificial rainfall simulation tests showed that the improvement of vegetation coverage could increase not only soil infiltration but also vegetation evapotranspiration,and then made the rainfall-induced runoff production decrease.Vegetation root system could increases the resistance ability of soil to erosion,and vegetation aboveground part could reduce raindrop kinetic energy and splash soil erosion.Therefore,with the increase of vegetation coverage,the rainfall-induced sediment could decrease.

A review of the research on complex erosion by wind and water

Complex erosion by wind and water, which is also called aeolian-fluvial interactions, is an important erosion process and landscape in arid and semiarid regions. The effectiveness of links between wind and water process, spatial environmental transitions and temporal environmental change are the three main driving forces determining the geomorphologic significance of aeolian-fluvial interactions. As a complex interrelating and intercoupling system, complex erosion by wind and water has spatial- temporal variation features. The process of complex erosion by wind and water can be divided into palaeoenvironmental process and contemporary process. Early work in drylands has often been attributed to one of two schools advocating either an ＇aeolianist＇ or a ＇fluvialist＇ perspective, so it was not until the 1930s that the research on complex erosion by wind and water had been conducted. There are two obstacles restricting the research of complex erosion by wind and water. Firstly, how to transform in different temporal and spatial scales is still unsettled; and secondly, the research methodology is still immature. In the future, the mechanism and control of erosion, the complex soil erodibility in wind and water erosion will be the focus of research on complex erosion by wind and water.

Spatial distribution of surface rock fragment on hillslopes in a small catchment in wind-water erosion crisscross region of the Loess Plateau

The cover and size distributions of surface rock fragment in hillslopes were investigated by using digital photographing and treating technique in a small catchment in wind-water erosion crisscross region of the Loess Plateau. The results indicated that the maximal cover of rock fragment was pre-sented at mid-position in steep hillslope. Rock fragment presented a general decreasing-trend along the hillslope in gentle hillslope. Rock fragment cover was positively related to gradient, rock fragment size decreased generally along the hillslope, and the size reduced with the gradient. The mean size of rock fragment was at a range of 6―20 mm in the steep hillslope, rock fragment size > 50 mm was rarely presented. The covers of rock fragment at different positions were markedly related to the quantities of rock fragment < 40 mm. The area of rock fragment of 2―50 mm accounted for 60% or more of the total area, dominating the distribution of rock fragment in the hillslopes.

北方农牧交错带风水蚀复合区水土流失现状与综合治理对策

风水蚀复合区是中国北方农牧交错带的一部分。区域的东面与南面毗邻水蚀地貌形态,东南界为沙漠化土地发生、发展的东南界;区域的西面与北面与风蚀地貌形态接壤,西北界为旱作农业的西北界。复合区包括74个县(旗),面积42.77万km2,总人口2400万(2004年)。主要生态问题为:沙漠化持续发展,沙尘暴频发;土地退化严重,承载力急剧下降;生态环境恶化,自然灾害频繁。复合区水土流失的主要特点表现为风水蚀在时间上交错,空间上叠加。受侵蚀营力系统与环境系统的制约,水土流失类型表现出明显的地域分异规律。2000年水土流失面积26万1517.35 km2,占全区土地面积的61.14%;复合区每年流失土壤11.97亿t,其中水力侵蚀量5.55亿t,风力侵蚀量6.42亿t。近20多年来,复合区大部分地区的水土流失面积有所减少,侵蚀强度有所降低。随着国家加大生态建设的力度,预计在未来的十到几十年,复合区的水土流失态势将呈现逐步逆转的趋势,但局部的水土流失状况依然很严峻。风水蚀复合区水土流失治理要以预防为主、保护领先为原则,生物措施、农业技术与工程措施相结合综合治理,把国家的生态需求与农户的经济需求相结合,依法协调经济开发与环境保护的关系,注重科学研究,提高科技含量。根据风水蚀复合区现状,提出了一些治理工程项目,主要包括复合区黄河粗泥沙综合治理工程和生态修复工程。这些工程的实施,将大大减少进入黄河的粗泥沙量,风水蚀复合区水土流失状况可以得到改善。

风水复合侵蚀研究述评

风水复合侵蚀或风水交互作用是干旱、半干旱地区常见的侵蚀过程。这种风力与流水对同一侵蚀对象(区域)的共同作用或交替作用塑造了风蚀水蚀交错区特有的侵蚀地貌景观。作为一个相互联系、影响的复杂系统,风水复合侵蚀具有明显的时空分布特征,其侵蚀过程可以划分为古代过程与现代过程。由于以往的风蚀和水蚀研究相互独立,风水复合侵蚀的研究起步较晚。在研究中存在着尺度转化与研究方法不成熟等问题。对风水复合侵蚀的机理与防治以及土壤复合可蚀性的研究都将成为今后研究中的重点与难点。

黑土区土壤风水复合侵蚀机理研究进展及展望

东北黑土区的水土流失问题十分严重,已经引起国内外众多专家学者的重视。黑土区土壤侵蚀通常是风力和水力交互作用的结果,以往的研究通常针对单一作用力,风蚀和水蚀的研究相互独立,很少进行风水复合侵蚀的机理研究。基于前人的研究成果,文章总结归纳东北黑土区关于风蚀、水蚀以及风水复合侵蚀的研究进展,并针对当前存在黑土区土壤侵蚀问题,提出关于黑土区风水复合侵蚀机理研究的建议,为黑土区未来的水土保持工作提供依据。

复杂地形区土壤侵蚀及其影响因子提取

相对与地形平坦地区,复杂地形区土壤侵蚀的提取存在较大的难度。RUSLE是目前应用最广泛的土壤侵蚀经验模型,但它只提供了一般条件下土壤侵蚀的提取方法。为了将RUSLE有效的应用在复杂地形区,需要对模型中相关侵蚀因子提取方法进行适当的调整。因此重点对受复杂地形影响严重的地形因子和作物覆盖与管理因子的提取方法进行研究,提出了更准确的提取方法。利用该方法对三峡库区的姊归县进行实验,结果表明,该方法可以有效提取土壤侵蚀信息。

黄土丘陵沟壑区坡长与地形复杂度关系研究

流域分布式土壤侵蚀学坡长作为流域和区域尺度水文模型和土壤侵蚀模型的最基本参数之一,对研究土壤侵蚀的形成和发展有重要影响。从黄土丘陵沟壑区的常用地形因子入手,详细探讨了坡长与地形之间的联系,在此基础上建立了地形要素交互作用的多维复合集成模型,并根据该模型定量计算出研究区各地形要素对坡长的贡献,进而揭示了地形对于水土流失的影响。研究表明:①复杂地形因子对于坡长的贡献率更高,更能揭示地形对于水土流失的影响;②7种复合地形因子,对于坡长的贡献正负不一;③地形因子对坡长的贡献率由高到低依次为坡谱信息熵、粗糙度、高程面积积分、起伏度、海拔标准差、平均坡度、剖面曲率、平面曲率、沟壑密度。

风水复合侵蚀与生态恢复研究进展

风水复合侵蚀是风力与水力共同或交替作用相互增强或者削弱的过程。从侵蚀区划分、驱动因素、侵蚀机理和生态恢复对策等方面论述了风水复合侵蚀的研究进展,简述了半干旱风水复合侵蚀区和海岸复合侵蚀区是两个影响最大的风水复合侵蚀区。晋陕蒙接壤区为半干旱风水复合侵蚀区的强烈侵蚀中心,在土地利用上属农牧交错区,生态环境极为脆弱。海岸复合侵蚀岸段分布广泛,侵蚀岸线在总岸线中所占比例较大。影响风水复合侵蚀的因素包括自然和人为因素,且地域差异显著。半干旱区风水复合侵蚀研究主要从侵蚀特点、土壤特性、侵蚀产沙、侵蚀能量研究等方面;海岸复合侵蚀区从侵蚀特征、风暴潮与海岸复合侵蚀关系等方面分析了取得的进展和存在的不足。总结了生物措施和工程措施对风水复合侵蚀区生态恢复的作用,展望了风水复合侵蚀与生态恢复的研究方向,并指出复合侵蚀机理与评估、生态恢复机理与评价研究是今后研究的趋势。

气候变化对风水蚀复合区的影响

风水蚀复合区作为农牧交错带的敏感区域,对气候变化有着显著的响应。通过实地考察和气象资料的分析,厘定了风水蚀复合区的概念并对其范围加以界定。由于风水蚀复合区区内气候类型复杂、侵蚀动力多样、风季和雨季的交错分布及其脆弱的生态环境,造成水土流失和沙漠化相当严重,并发育了独特的地貌景观。风水蚀复合区的界限受降水的影响而呈南北摆动,干旱年,向东南方向移动;多雨年,向西北方向移动。