红壤缓坡花生地不同水土保持措施效果分析

采用径流小区试验,以花生常规种植为对照,研究红壤荒坡花生地花生+草篱、花生+覆盖+草篱、花生+覆盖3种种植措施的水土保持效果.试验从4月份花生种植后开始测定,8月底花生收获结束.结果表明:1)3种种值措施地表径流量均随日降雨量的增大而增大;2)3种种植措施地表径流量、土壤侵蚀量均与对照差异显著(P＜0.01).表明,花...     

Trend and uncertainty analysis of simulated climate change impacts with multiple GCMs and emission scenarios

Trends and uncertainty of the climate change impacts on hydrology, soil erosion, and wheat production during 2010-2039 at El Reno in central Oklahoma, USA, were evaluated for 12 climate change scenarios projected by four GCMs (CCSR/NIES, CGCM2, CSIRO-Mk2, and HadCM3) under three emissions scenarios (A2, B2, and GGa). Compared with the present climate, overall t-tests (n = 12) show that it is almost certain that mean precipitation will decline by some 6% (>98.5% probability), daily precipitation variance increase by 12% (>99%), and maximum and minimum temperature increase by 1.46 and 1.26 °C (>99%), respectively. Compared with the present climate under the same tillage systems, it is very likely (>90%) that evapotranpiration and long-term soil water storage will decease, but runoff and soil loss will increase despite the projected declines in precipitation. There will be no significant changes in wheat grain yield.Paired t-tests show that daily precipitation variance projected under GGa is greater than those under A2 and B2 (P = 0.1), resulting in greater runoff and soil loss under GGa (P = 0.1). HadCM3 projected greater mean annual precipitation than CGCM2 and CSIRO (P = 0.1). Consequently, greater runoff, grain yield, transpiration, soil evaporation, and soil water storage were simulated for HadCM3 (P = 0.1). The inconsistency among GCMs and differential impact responses between emission scenarios underscore the necessity of using multi-GCMs and multi-emission scenarios for impact assessments. Overall results show that no-till and conservation tillage systems will need to be adopted for better soil and water conservation and environmental protection in the region during the next several decades.     

控制坡地水力侵蚀危害的管理措施

根据坡面水力侵蚀由降雨击溅力和径流侵蚀力作用于坡面土壤,从而引起土壤颗粒的剪切破坏分离,被径流携带引起流失的作用机理,从植被覆盖、人工覆盖、消减径流量、减小径流流速、增强土壤抗分散、抗剪切能力等方面入手,采用适宜的生物、工程、耕作及化工产品综合措施,达到防止或减轻坡面侵蚀,保护土地生产力之目的。     

坡面水蚀过程的力能体系及研究思路

通过对作用于水蚀过程中力能变化的分析,重点描述了雨滴击溅力、坡面径流力、土粒黏结力、地表摩擦力的计算方法及作用过程和主要影响因子,对于表达式中各参数,设计出确定其数值的实验方案。     

Study on Mechanical Properties of High-Performance Concrete

In this paper the high-performance concretes with 56-day compressive strengths of 60 to 100 MPa (with or without silica fume) have been studied experimentally in order to develop information about the mechanical properties of high-performance concrete. Results and discussions are presented regarding compressive strength gain with time,effect of drying. A linear equation of static modulus of elasticity has been derived.The static modulus of elasticity and Poisson's ratio are calculated by regression with testing data of 20 specimens.     

地形起伏对气流速度影响的风洞实验研究

地形起伏主要通过对气流的扰动极大地影响着土壤风蚀特征。通过对4 种坡度下气流变化的风洞实验,发现坡面对气流的影响表现在两个方面,一是气流在爬坡过程中的速度除在坡角点略有下降外,整体上呈逐渐加强趋势,速度增加率与坡长呈良好的线性关系;二是在垂直方向上速度的增加率符合对数规律。前者使风蚀程度加强,后者使风蚀程度减弱,二者共同制约着坡面上土壤的风蚀特征。     

黄土高原第四纪期间水土流失的地质记录和基本规律

黄土高原保存有许多第四纪期间水土流失的地质记录,这些记录表明,50万年以来,黄土高原至少有5个水土流失十分强烈的时期,它们分别出现在0.70～0.50Ma B.P、0.2～0.25Ma B.P、0.14～0.08Ma B.P、0.01～0.015Ma B.P和0.006～0.002Ma B.P等气候温暖湿润的阶段,说明影响黄土高原水土流失的主要原因是气候条件。     

泥河沟土壤侵蚀动态航空遥感制图的研究

利用两期不同年代航空遥感信息源,编制两期土壤侵蚀类型现状图,经过叠合比较,建立动态分类系统,勾绘编制的动态图,能够准确、直观地反映出两个年代,特定区域土壤侵蚀类型空间分布的变化规律、趋势和数量特征,为评价土壤侵蚀,水土保持规划和综合治理决策提供科学依据。结果表明,这种方法合理可行,速度快,精度高。     

子午岭地区自然区域特征及其与土壤侵蚀的关系

在对子午岭地区进行全面考察的基础上,分析研究了子午岭地区区域自然环境的基本特征,指出:子午岭地区地质条件复杂,构造运动强烈、岩性疏松、地貌类型齐全、沟深坡陡、降水丰沛、降雨强度大、冲刷强烈,具备了各科侵蚀过程的发生条件。但由于地面覆盖着良好的植被,侵蚀很轻微。子午岭地区作为黄土高原植被恢复的样板表明,大力恢复黄土高原地区的植被,是黄土高原水土保持的核心和中心任务。     

长武王东试验区道路侵蚀及其防治途径

本文通过野外调查、航片判读、野外人工径流冲刷试验,并结合土壤容重室内试验资料,对影响道路侵蚀的因素进行了综合分析。道路侵蚀是导致高原沟壑区沟头迅速延伸、地形更加破碎的主要原因之一,因此,以道路侵蚀防治为中心,并采用一系列综合防治措施是搞好本区域土壤保持工作的重点。