不同硝酸钾溶液浓度对垂直一维入渗特性影响研究

通过室内不同浓度溶液的垂直一维入渗试验,分析了不同浓度碳酸钾溶液影响下的湿润锋和累积入渗量的变化规律以及土壤含水量和硝态氮浓度的分布规律,由不同浓度溶液累积入渗量,依据GREEN-AMPT入渗模型,反推出湿润锋面平均吸力和饱和导水率,结果表明增大溶液浓度提高了垂直一维入渗的饱和导水率,但减小了湿润锋面的平均吸力,溶液浓度通过影响湿润体的饱和导水率和湿润锋面的平均吸力来影响入渗量,二者的综合作用是增大了入渗量。     

Effects of different land use types on infiltration capacity in a catchment in the highlands of Ethiopia

Infiltration capacity is an important variable for understanding and predicting a range of soil processes. This study investigated for different slope positions the effects of forest conversion to cultivation and grazing on soil infiltration capacity. Infiltration capacity was measured in the field in each land use type using a double‐ring infiltrometer. A total of 108 soil samples (3 slope positions × 3 land use types × 4 soil profiles × 3 soil depths) were collected to determine the variables that affect infiltration capacity viz. particle size distribution, organic carbon content, dry bulk density and soil moisture content. The results showed that in the cultivated and grazed land compared with forest, infiltration capacity and soil moisture content were 70 and 45% smaller respectively, and dry bulk density was 13–20% larger. Changes in soil structure caused by surface soil compaction because of tillage and animal trampling coupled with a smaller soil organic carbon content, are likely to be the principal factors causing the decline in infiltration capacity and soil moisture content after conversion of forest to cultivation and grazing.     

Effect of Gypsum Application on Long Term Changes in Soil Properties and Crop Growth in Sodic Soils under Field Conditions

In a field study, conducted on farmer's waste sodic soils, Aquic Natrustalf, 12.5 t/ha gypsum was surface mixed. Effect of gypsum application on soil properties and crop yields of rice and wheat grown in succession was evaluated after one to five years of gypsum application. The results showed that soil pH, electrical conductivity, calcium carbonate and soil dispersion decreased, whereas organic carbon, hydraulic conductivity, water infiltration and storage increased considerably after five years of gypsum application. In the initial years the improvement in soil properties was more in the surface layers and extended to lower layers slowly in the following years. Average grain yields of rice and wheat in the first year were 4.2 and 1.8 t/ha, respectively. The yields further increased to 6.1 and 2.5 t/ha in the 5th year, but the yields were lower than the yields obtained in research experiment. Relationships between wheat grain yield and pH of 0–15 and 15–30 cm layers were established. Wheat yield reduced by 45 percent when pH of 0–15 cm layer increased from 9.0 to 9.5. The sodicity of sub soil was still too high to permit the cultivation of deep rooted crops even after five years of gypsum application. Normal crop production is possible in these sodic soils, given sufficient time to reduce the sub soil sodicity.     

畦田Philip入渗参数和田面综合糙率同步推求

以水量平衡原理为基础,通过对畦灌地表水面线的概化,并将Philip入渗公式等同为α=0.5的Kostiakov修正模型,由此建立了利用畦灌水流推进过程同步推求Philip土壤入渗参数和田面综合糙率的模型.结合文献资料和大田试验对所建模型进行验证,并采用Matlab软件求解,得出不同地表储水形状系数σh下的入渗参数和糙率,并分别对入渗参数和田面综合糙率的可靠性进行了验证,结果表明所建模型同步推求土壤入渗参数和田面综合糙率是可靠的,并且计算方便,精度较高.     

砂土中粘土夹层对入渗过程影响的试验分析

对水在高渗透性砂内入渗过程中,其内部的低渗透性粘土夹层对入渗过程的影响进行了室内垂直一维入渗试验。通过分析定性得出粘土夹层对入渗过程的影响体现为减渗作用,表现为粘土夹层将均质粗砂中的非线性入渗过程变为夹层内的线性入渗过程,使夹层范围的入渗为一个具有较小入渗率和较小湿润锋推进速度的稳渗阶段。     

环境因子对土壤水分渗透特征的影响

采用双环法,研究不同地形条件(坡度、坡位、坡向)、降雨等因子对土壤渗透特征的影响。研究结果表明,土壤渗透速率具有明显的坡面垂直变异规律,随着坡度的增加,土壤的渗透速率减小,达到稳渗的时间延长,但是坡度大于20°以后,稳渗速率反而升高;阳坡土壤的初渗速率大于阴坡,而阴坡土壤的稳渗速率大于阳坡;不同坡位条件下的试验表现出从坡上部到坡下部,土壤渗透速率随坡位下移呈逐渐降低的趋势;降雨前土壤的初渗速率和稳渗速率均大于降雨后土壤的初渗速率和稳渗速率,降雨前土壤达到稳渗所需时间比降雨后长。     

诗画对中国古典园林的影响

中国古典园林深受绘画、诗词和文学的影响.中国古典园林一直是循着绘画的脉络发展起来的.绘画理论对于造园起了很大的指导作用,诗词也对中国造园艺术影响至深.本文论述、分析了诗歌、绘画对中国造园艺术的影响,体现出中国古典园林艺术追求诗情画意的美学意味和独特的美学传统.     

毛乌素沙地土壤水分特征曲线和入渗性能的研究

采用张力计法测定了毛乌素沙地低吸力段土壤水分特征曲线,并用θ=aψ-b模型进行了拟合,分析了各层次土壤的持水和供水能力.结果显示0～20 cm的土壤持水能力最差,但供水能力最强,40～60 cm的土壤持水能力最强,供水能力一般;当土壤吸力达到0.06～0.08 MPa,即土壤容积含水率在1%～3%时,比水容量就已达到了10-1级,标志着土壤水分处于难效水阶段,植物利用比较困难;在室内采用环刀法测定了沙地土壤水分的入渗率,结果显示有植被覆盖的试验区的初始入渗率、稳定入渗率和累积入渗量都比无植被覆盖的对照区大,说明该地区植被对土壤水分的消耗影响显著.     

北京九龙山林地对降雨的调蓄功能*

对北京九龙山油松林、侧柏林、阴坡灌木林、阳坡灌木林的林冠层、枯落物层及土壤层对降雨的调蓄功能进行了研究，结果表明：四种不同林地的林冠截持率为２２％～３２％，大暴雨下的截持率为７％～１０％；枯落物层的有效调蓄为０．４６～２．４２ｍｍ；５０ｃｍ土层的快速、慢速和变化调蓄量分别为３５～４８ｍｍ；５４～４８ｍｍ，２８～５２ｍｍ；四种林地调蓄功能的顺序从大到小为油松林、阴坡灌木林、阳坡灌木林、侧柏林。     

Impacts of fractal features of soil on moisture infiltration capacity of typical stands in Jinyun mountain of Chongqing city

The soil structure was expressed with fractal dimensions of particle size distribution (PSD), aggregate size distribution (ASD), and soil pore size distribution (SPD). The effect of soil fractal features on soil infiltration velocity and process was studied. The result of the fractal feature shows that fractal dimensions of PSD are obviously greater than those of ASD and SPD, and in different soil genetic horizons, the fractal dimension of ASD has the greatest variability, and shows a downtrend on the top-to-bottom genetic horizon. According to the soil infiltration process curve, the infiltration process was divided into three phases: (1) the initial phase (0–5 min), (2) the transition phase (5–30 min), and (3) the stable phase (30–180 min). In the initial phase of infiltration, the soil structure of soil genetic horizon A was the major influencing factor; in the transition phase of infiltration, the pore distribution of soil horizon AB and soil structure of horizon B were the major influencing factors; in the stable phase of infiltration, the soil structure of horizon C was the major influencing factor to the infiltration velocity. Soil infiltration process is influenced comprehensively by soil PSD, ASD, and SPD. In the overall soil water infiltration, the infiltration in shrub forest land was much faster than that in other land uses, and in the initial infiltration phase, arable land soil infiltration was much faster than that in forest land, and in the stable infiltration phase, the infiltration velocity in forest land was faster than that in arable land. __________ Translated from Journal of Beijing Forestry University, 2006, 28(3): 73–78 [译自: 北京林业大学学报]