土壤干密度和含水率对2种紫色土抗剪强度的影响

选择广泛分布于重庆丘陵山区的钙质紫色土和中性紫色土2种土壤,通过室内三轴剪切试验测定含水率和干密度交互作用对土壤抗剪强度指标的影响。结果表明:(1)在相同干密度情况下,2种土壤粘聚力(c)随着含水率增加呈现出先增加后减小的趋势,在相同土壤含水率水平下,土壤粘聚力(c)随干密度增大而增大;2种土壤内摩擦角(φ)在各干密度条件下均随着含水率增加呈明显减小的趋势。(2)含水率和干密度的交互作用对粘聚力(c)有显著影响,粘聚力(c)随着干密度的增大而增大,且每一个干密度都有一个含水率与之对应,并在此交互条件下c达到最大。钙质紫色土粘聚力(c)在干密度为1.7g/cm3,含水率为11%时达到极大值,此时粘聚力(c)为154.59kPa,中性紫色土粘聚力(c)在干密度为1.6g/cm3,含水率为8%时达到极大值,此时粘聚力(c)为126.38kPa。(3)含水率和干密度的交互作用对内摩擦角(φ)影响相对较小,同一干密度下,其φ值差异不大,随干密度的增大缓慢增大,相对而言,含水率对内摩擦角(φ)的影响更明显。钙质紫色土内摩擦角(φ)随含水率的增大呈曲线下降,中性紫色土内摩擦角(φ)随含水率增大有一个短暂的增大过程,而后随之迅速减小。     

冀西北地区白桦根系-土壤界面摩擦性能

林木根系通过摩擦锚固作用实现对土体的固持.以冀西北地区白桦的根系为对象,通过垂直拉拔试验,探究根径、根系土中埋深、土壤含水率、海拔、根系生长方向等因素对根系-土壤界面摩擦性能的影响.结果表明:根土摩擦力随着埋深、根径的增大而增大,同根系直径满足幂函数关系,决定系数大于0.82,拟合良好;土壤含水率由11.85％增大至1...     

柠条锦鸡儿细根表面积密度对土壤水分空间分布的响应

为研究柠条锦鸡儿(Caragana microphylla)细根与土壤水分的空间关系,以内蒙古农牧交错带10 a生柠条锦鸡儿细根为研究对象,对细根表面积密度与土壤含水率之间的关系进行了初步探讨。分别对柠条锦鸡儿细根和土壤水分的空间分布情况进行研究发现,垂直和水平土层方向各标准地柠条锦鸡儿细根表面积密度与土壤含水率均呈极显著相关,相关系数均大于0.65(P0.01)。经回归分析建立柠条锦鸡儿细根表面积密度与土壤含水率之间的关系模型并对模型进行验证,验证结果发现该模型可以很好地描述两者之间的关系(R~2=0.84,P0.01)。撂荒地土壤含水率比柠条地高71%,研究区柠条地出现至少200 cm的土壤干层,部分土层接近凋萎湿度,柠条生长受阻。研究结果对于干旱区人工柠条林的栽植管理具有重要意义,可为北方农牧交错带生态环境建设及植被恢复提供理论依据。     

密度和含水率对固化土无侧限抗压强度的影响

 为给修建土壤固化剂集流面的施工工艺提供科学依据,采用正交设计方法,对密度和含水率影响固化土强度的规律性进行试验研究。试验分析结果表明:密度对固化土强度的影响大于含水率;随着密度的增大,固化土的强度呈直线上升;在同一密度下含水率在最优含水率的80%±5%范围内时,固化土的强度达到最大。在实际施工过程中,建议尽可能的增加固化土的密度,压实度控制至少超过0.94;混合料的含水率控制在最优含水率的80%～90%之间。     

土壤水分对植物根-土界面相互作用特性的影响

为研究不同土壤水分下不同植物根系与土壤界面的摩阻特性,使用直剪仪对内蒙古中西部的5种典型乡土植物(柠条、沙棘、杨柴、紫花苜蓿和沙打旺)的根系在不同土壤含水率下进行根-土界面直剪摩擦试验。结果表明:当土壤含水率在4.5%~24.5%时,5种植物根-土界面摩擦系数均大于素土的土-土界面的值,且随着土壤含水率的增加,根-土界面和土-土界面摩擦系数均呈下降趋势,其中沙棘根-土界面的摩擦系数和黏聚力均大于其他4种植物的值,表明仅从根系与土壤间的相互作用特性来看,沙棘根系固土抗蚀的作用明显优于其他4种植物。根-土界面和土-土界面黏聚力均随着土壤含水率的增加呈先增后减的变化特征,且植物种不同黏聚力峰值出现时对应的土壤含水率亦不同。     

土壤含水率对枳椇生长发育的影响

采用地面光谱采样与土壤采样同步进行的方法,对不同类型的林分土壤水分进行了定量分析,得出不同立地类型土壤含水量差异以及含水量变化与枳椇生长趋势的关系。影响枳椇成活与生长的主要矛盾是土壤水分,雨季生长量随着土壤水分的增加而增加。不同立地类型土壤含水量差异是非常明显的,其排序依次为:壤土>沙土,稍阴土壤>全阳土壤。     

土壤含水率与土壤碱度对土壤抗剪强度的影响

土壤含水率和土壤碱度是表征土壤物理化学性质的两个重要参数。通过室内三轴不固结不排水试验,研究了土壤含水率和土壤碱度对土壤抗剪强度的影响。试验处理采用5种土壤碱度(土壤可交换钠百分比ESP=0、5、10、20、40)和4种土壤质量含水率(0.05、0.10、0.20以及饱和含水率0.34)水平。试验结果显示,土壤黏聚力随着土壤含水率的增加基本上呈先增大后减小之趋势;当土壤含水率在0.10附近时黏聚力达到其最大值。土壤内摩擦角随着土壤含水率的增加而线性减小。土壤碱度对土壤黏聚力的影响机理较为复杂,其影响效果随土壤含水率的增加而减小;但土壤碱度对土壤内摩擦角的影响较小。土壤碱度对土壤抗剪强度的影响程度明显地小于土壤含水率对其的影响程度。     

苗期土壤含水率变化对冬小麦根、冠生物量累积动态的影响

为合理进行冬小麦生长过程的适时水分调控，该文对不同生育期土壤含水率对冬小麦根冠影响的试验进行分析。采用的试验包括5种水分处理，即苗期充分供水，其它生育期进行中度胁迫(FB)、重度胁迫(FC)处理和从苗期开始的中度水分胁迫(SB)、重度水分胁迫(SC)处理以及全生育期充分供水的对照处理。试验结果表明：苗期土壤含水率对冬小麦根、冠的生物量，生物量的累积速率产生不同影响，使全生育期内根、冠占植株总量的比例和根冠比发生改变。当苗期水分改变时，生育初期，根、冠均没有明显响应，但到播后16 d，播后20 d，根、冠生物量分别随胁迫程度的增加而减小(FB>SB，FC>SC)；在播后28 d，SB和SC的根系质量累积速率超过对应FB和FC处理，且苗期受胁迫处理的冬小麦在生殖生长阶段所维持的根系大于苗期不受胁迫处理的根系；冠的累积速率则在播后28 d和35 d也出现SB>FB，SC>FC的结果，到播后42 d，SB、SC的冠质量分别超过对应的FB、FC的冠质量。在此过程中，根、冠生物量占总质量的比例发生改变，根表现为SB>FB，SC>FC；冠在营养生长阶段FB>SB，FC>SC，在生殖生长期SB达到最大；相应根冠比改变。     

根土界面磷酸盐的分布与移动

The experiments were conducted in the artificial climate laboratory using 32P labelled soil and soil-root plane system to investigate phosphate distribution and its movement in the soil-root interface zone and their relations with phosphate uptake by plant as well as transpiration rate (atmosphere humidity).It was found that although the phosphate in the soil-root interface zone was of depletive distribution as a function C/Co=ax^b(C/Co is the relative content of fertilizer phosphate in a distance from the root surface x,a and b are the regression constants),and a relative accumulation zone of phosphate within 0.5 mm near the root surface was often boserved especially in the heavier texture soils because of root phosphate secretion.The depletion intensity of phosphate in the soil-root interface zone was in agreement with the phophate uptake by plants under two humidities very well.However,the effects of air humidity on characteristics of the phosphate distribution near wheat or maize root surface were different.Wheat grew better under lower atmosphere humidity while maize,under higher humidity,which caused a more intensive uptake and thus a stronger depletion of phosphate in the rhizosphere,Moreover,the depletion intensity was greater by the bottom or the middle part of wheat roots and by the top or the middle part of maize roots.The depletive distribution of phosphate in the rhizosphere soil and the relative contribution of phosphate diffusion to plant,which was more than 98% in the cultural experiments,indicated that diffusion was a major process for phosphorus supply to plants.     

油松群根与土壤界面摩擦特性研究

通过对油松群根施加拔出荷载进行直接拉拔实验,分析群根根系中分叉根直径、分叉角度对拔出过程中油松根系与土壤摩擦锚固性能的影响。结果表明:群根的L-S曲线与单根的曲线存在明显的差异,分叉根直径之和与最大摩擦锚固力呈明显的线性正相关关系;且在分叉根直径和与分叉角度变化不大时,直径之差越小,根土摩擦力越大;在分叉根直径和较接近时,群根根土摩擦力随着分叉根夹角增大而增大。     

Modeling of maximum dry density and optimum moisture content of stabilized soil using artificial neural networks

This study considers the use of artificial neural networks (ANNs) to predict the maximum dry density (MDD) and optimum moisture content (OMC) of soil‐stabilizer mix. Multilayer perceptron (MLP), one of the most widely used ANN architectures in the literature, is utilized to construct comprehensive and accurate models relating the MDD and OMC of stabilized soil to the properties of natural soil such as particle‐size distribution, plasticity, linear shrinkage, and the type and quantity of stabilizing additives. Five ANN models are constructed using different combinations of the input parameters. Two separate sets of ANN prediction models, one for MDD and the other for OMC, and also a combined ANN model for multiple outputs are developed using the potentially influential input parameters. Relative‐importance values of various inputs of the models are calculated to determine the significance of each of the predictor variables to MDD and OMC. Inferring the most relevant input parameters based on Garson's algorithm, modified ANN models are separately developed for MDD and OMC. The modified ANN models are utilized to introduce explicit formulations of MDD and OMC. A parametric study is also conducted to evaluate the sensitivity of MDD and OMC due to the variation of the most influencing input parameters. A comprehensive set of data including a wide range of soil types obtained from the previously published stabilization test results is used for training and testing the prediction models. The performance of ANN‐based models is subsequently analyzed and compared in detail. The results demonstrate that the accuracy of the proposed models is satisfactory as compared to the experimental results.     

有机肥料BGA激活剂对日光温室内土壤含水率的影响

探讨了日光温室中施用有机肥料BGA激活剂后土壤水分动态规律,试验结果表明BGA激活剂作为一种有机肥料对于保持土壤水分有着明显的作用,施加BGA的土壤含水率要比对照处理高出17.7%;施加BGA后通过水分运移,在根系分布密集的20～60 cm之间的土壤含水率较高,其中20～40 cm的土壤含水率增加26%,40～60 cm的土壤含水率增加28%;试验研究发现,当BGA的施加标准为150 g/株,作物根系土层含水率增加最多.BGA作为一种有机肥料,为发展节水农业提供了一种新的途径.     

花岗岩剖面土壤崩解特性与初始含水率的关系

土壤的崩解特性是南方红土区土壤侵蚀的重要指标,也是开展水土保持工作的重要依据.作者选择花岗岩发育的2个土壤剖面,分别采集淋溶层、淀积层、过渡层和母质层原状土壤样品.利用崩解仪进行崩解实验,测定剖面不同层次土壤崩解特性与初始含水率的关系.结果表明:在不同的初始含水率条件下,土壤崩解特性均表现为淋溶层和淀积层土壤崩解缓慢,过渡层和母质层崩解迅速;初始含水率的递变,对淋溶层和淀积层土壤达到崩解完全所需用时影响较大,对过渡层和母质层土壤影响较小;随着初始含水率的减小,淋溶层和淀积层的最大崩解量逐渐增加,风干状态时可趋于完全崩解;过渡层和母质层均可全部达到完全崩解,初始含水率对其影响较小.研究结果可为治理南方崩岗水土流失提供依据,也为探索崩岗的发生机制提供参考.     

黄土区刺槐和油松水土保持林合理密度的研究

 以黄土区刺槐和油松水土保持林为研究对象,在对水分循环要素进行长期监测的基础上,以水分亏缺量为依据,利用径流林业的基本原理,结合林分调查结果,提出了利用胸径计算刺槐和油松林合理密度的公式。利用该密度参考值管理刺槐和油松水土保持林,可以保证林木正常生长所需水量,不会造成林地土壤干化。同时以刺槐和油松林地的土壤水分含量、最低含水量和难效水频率为指标,提出了黄土区适宜的刺槐和油松水土保持林的管理密度。     

初始含水量和容重对黑土压缩特性的影响

东北黑土区农业机械化水平高,农机作业压实导致的土壤结构和物理性状退化问题日益严重,压缩特性是定量分析土壤压实过程的有效手段,但目前黑土压缩特性随初始含水量和初始容重的变化规律尚不明确。为了解初始含水量和初始容重对黑土压缩特性的影响程度及其变化关系,该研究以重塑黑土为对象,设0.15、0.20、0.25、0.30、0.35、0.40 g/g共6个初始含水量水平,设1.00、1.10、1.20、1.30、1.45、1.60 g/cm³共6个初始容重水平,使用固结仪进行单轴压缩试验测定土壤压缩曲线,分析初始含水量和容重对压缩特性影响。结果表明,土壤初始含水量、容重及两者交互作用均极显著影响重塑黑土压缩特性(P<0.001),据此建立了预测压缩特性的土壤传递函数。黑土的预固结压力为10.42～1 106.17 kPa,与初始含水量显著线性正相关、与初始容重显著线性负相关(P<0.05);压缩指数为0.311～0.852,与初始含水量和容重呈二元多项式方程的关系,随初始容重的增大而降低,在中等含水量时最大;回弹指数为0.007～0.321,与初始含水量正相关,与...     

不同水分条件下水稻根解剖结构的比较分析

在旱作和淹水两种培养方式下,研究了5种基因型水稻(Oryza.sativa.L.)(常规粳稻、杂交粳稻、常规籼稻、杂交籼稻和旱稻)幼苗根系解剖结构的差异。结果表明,两种水分条件下,水稻根通气组织的形成和皮层厚壁细胞的形态均存在基因型差异。5种基因型间,淹水条件下杂交粳稻根形成通气组织的时间最晚,根皮层厚壁细胞形态上的差异在常规粳稻和常规籼稻之间表现得更为明显;旱作条件下旱稻的根通气组织形成较其他基因型晚,常规粳稻根皮层厚壁细胞排列疏松,细胞壁加厚程度小。与淹水条件相比,旱作条件下杂交稻根通气组织形成较迟,常规粳稻根皮层厚壁细胞排列较疏松。     

模拟降雨条件下保水剂对沙质土壤水分的影响

为了探究保水剂对沙质土壤水分的影响,采用室内重建土柱,在人工模拟降雨条件下研究不同用量保水剂对沙质土壤(0~30 cm)含水率的影响。结果表明:土壤含水率随着保水剂用量的增加而增加,保水剂用量为0.2%时不但省时省力,而且0~10 cm、10~20 cm、20~30 cm 3个土层土壤含水率分别为45.42%、48.48%、46.16%,既能满足植物的生长需要,又能节省经济成本,可为干旱、半干旱区节水造林及保水剂的合理使用提供理论依据。     

Differences between field-monitored and laboratory-measured soil moisture characteristics

A soil water retention curve (SWRC) is usually measured in a laboratory (lab SWRC), and is used to analyze in-situ soil moisture conditions. However, it is rarely verified whether and how a lab SWRC is in agreement with its equivalent relation between matric potential (h) and volumetric water content (θ) in a natural field (in-situ SWRC). In addition, most SWRCs show moisture hysteresis through which the drying process gives a larger θ at a given h than the wetting process, while an in-situ SWRC must be produced through the cycles of drying and wetting in the field. Thus, it can be hypothesized that an in-situ SWRC shows a lower value of θ than a lab SWRC for any h that the soil layer ordinarily experiences. To give experimental proofs for this hypothesis, this study aimed at quantifying seasonal behaviors of in-situ SWRCs and at comparing them with their corresponding lab SWRCs. To obtain a series of in-situ SWRCs, the h and θ were coincidently monitored at four points with three depths each in a meadow for 2.5 years using tensiometers and a capacitance-type soil moisture sensing system. As the equivalent to the in-situ SWRCs, the lab SWRCs were also measured. The in-situ SWRCs tended to have roughly 10% smaller θ than the lab SWRCs for the series of h observed in the study site, suggesting that an in-situ SWRC can hardly be reproduced by a lab SWRC only. In addition, when the driest condition in the recent 3 years was exerted on the study site, some in-situ SWRCs shifted along the θ axis on the θ(h) charts, suggesting that the most dried condition had changed the soil moisture regime of these soil layers, resulting in the reduction of monthly or annual means of soil water content in the field. Since the shifts of the in-situ SWRCs were accompanied by the increases in both the gradients ‘dθ/dh’ and the variation of measured h, it was implied that an extraordinary drying of a soil layer promotes the development of soil pore structure or an increase in the fraction of plant available water.     

秸秆粉碎氨化还田对土壤体积质量及持水特性的影响

为尝试解决秸秆还田中秸秆分解缓慢、易诱发病虫害及与作物争氮等问题,通过室内土柱培养试验对比研究了秸秆粉碎程度及秸秆不同C/N值对自身分解速率、土壤体积质量、土壤持水特性的影响。结果表明：短期内秸秆粉碎程度对秸秆分解速率影响不大,但粉碎秸秆在试验后期分解速率明显高于长秸秆,氨化措施可显著加快秸秆的分解速率;粉碎秸秆对土壤体积质量的减小作用明显较长秸秆为好,在整个试验期,粉碎氨化秸秆处理的土壤体积质量均显著低于同时期其他处理;各处理土壤持水能力差异不大,但粉碎氨化秸秆能明显增强土壤耐旱性。该结果为探索一种能最大效益发挥秸秆改良土壤作用的秸秆还田新方式提供了一定的参照。