基于X-ray μCT技术的玉米籽粒结构特征的粒位效应分析

玉米籽粒因其在果穗上着生位置不同存在较大差异,明确籽粒结构特征的粒位效应为玉米的消费、加工和播种质量等玉米产量和品质性状的评价提供参考。该研究以3个不同籽粒类型的玉米品种登海618（DH618）、KX3564和先玉335（XY335）为材料,利用X射线计算机断层（X-ray micro-computed tomography,X-ray μCT）技术扫描测试样本,通过图像滤波、阈值分割等图像分析方法重建籽粒3维结构,获取玉米果穗不同粒位籽粒的胚、胚乳、皮下空腔、胚空腔、硬质胚乳、粉质胚乳、胚乳空腔等结构参数。数据分析表明,籽粒不同结构指标在果穗上呈现不同的变化规律,从基部到顶部（不考虑果穗两端的极端籽粒）,胚、胚乳及硬质胚乳体积线性下降,各指标在果穗上的变化范围分别为15.82～33.36、180.15～296.50及87.13～166.00 mm3;胚乳空腔>皮下空腔>胚空腔,果穗中部籽粒的空腔较小且稳定,3个品种表现一致;胚与胚乳的比值在粒位间基本稳定,粉质胚乳体积、硬质胚乳与粉质胚乳的比值从基部至顶部逐渐减小,但不同指标的变化斜率存在差异。3个供试品种的籽粒结构参数不同：DH618果穗不同部位籽粒胚与胚乳的比值大于KX3564和XY335,XY335籽粒硬质胚乳与粉质胚乳的比值大于DH618和KX3564。在籽粒空腔方面,KX3564皮下空腔的比例较高,而XY335胚乳空腔的比例较高。3个品种胚、胚乳、皮下空腔体积在玉米籽粒中的比例平均分别为9.27%、89.87%、0.86%。X-ray μCT扫描技术为玉米籽粒性状的研究提供新的方法与思路,明确果穗籽粒结构的粒位效应有利于全面地掌握玉米果穗上籽粒的性状特征,为玉米的生产、加工及品种改良等提供借鉴。     

泾阳南塬黄土滑坡的运动规律与液化效应

[目的]查明滑坡的运动特征及其影响因素,探讨滑坡的运动规律与内在机制,为区域防灾减灾工作提供理论借鉴。[方法]以泾阳南塬黄土滑坡为例,通过现场调查及槽探查明了滑坡的运动特征,采用统计学方法分析了滑坡的运动规律,在此基础上,探讨引起滑坡运动特征分异的"液化效应"。[结果]按照运动特征将泾阳南塬黄土滑坡划分为流滑型和滑动型两类,流滑型滑坡的滑距一般为坡高的4倍,滑动型滑坡的滑距约为坡高的2倍。1.50×10~5 m~3可近似的认为是研究区内"足以形成最大液化程度的最小滑体体积"。[结论]滑体体积及边界条件对滑坡运动液化影响显著,一般情况下滑坡体积越大、滑动边界越简单,运动液化程度就越高,运动距离也就越远;而体积越小、滑动边界越复杂,运动液化程度就越低,运动距离也就越近。     

土壤裂隙研究的回顾与展望

土壤裂隙的发育是土壤自身内在属性在外界条件变化时综合作用的结果,与土壤物理、化学及生物性质息息相关,对农田水肥蓄积、坡体稳定、地下水污染等的危害很大。本文首先阐释了土壤裂隙的内涵及其与孔隙之间的区别与联系,而后从形成机制的角度对土壤裂隙进行了分类,并归纳总结了水平裂隙和垂直裂隙的描述方式及裂隙的评价指标体系,接着对干缩裂隙发育的外因及内因做了较深入的讨论,最后对土壤裂隙日后研究工作的重点提出了建议,旨在为土壤裂隙研究提供有益借鉴。     

土壤中裂隙与其它类型孔隙结构差异的图像比较

裂隙是孔隙的一类。文章利用土壤切片的数字图像，采用目视分离的方法，比较研究了裂隙与其它类型的孔隙在结构上的差异。选择的土样研究结果表明，目视分离裂隙的方法是可行的，土体中的裂隙直径分布曲线是不规则的，而其它类型的孔隙直径分布曲线则类似对数正态分布；土壤总孔隙中直径较大的部分主要由裂隙构成，直径较小的部分则由其它类型孔隙和裂隙共同构成；土壤表面裂隙与土体内部裂隙在结构上可能具有一定差异。     

黄土高原旱地苹果园油菜间作对土壤大孔隙结构的影响

采用X-ray computed tomography(CT)技术研究了果树行间不同油菜间作密度(CK:清耕;L:低密度间作;M:中密度间作;H:高密度间作)对土壤大孔隙特征参数的影响。结果表明:油菜间作改善了果树行间(0—60 cm)土壤大孔隙特征,各土层的土壤大孔隙数量、大孔隙面积、大孔隙度等参数分别较清耕显著提高(P<0.05);不同间作密度对土壤大孔隙的作用不同,除10—20 cm外,中密度间作对土壤大孔隙度的改善效果均显著好于其他处理;中密度处理下大孔隙(d>1 mm)在各土层间的数目多、差异小,并且在0—30 cm土壤剖面上的成圆率最高。中、高密度油菜间作的土壤大孔隙特征参数均优于清耕及低密度间作,而中密度间作的土壤大孔隙分布更均匀、形状更规则,是黄土高原旱地苹果园改善土壤结构的适宜间作密度。     

基于CT的青海湖流域芨芨草草地土壤大孔隙特征分析

为探究青海湖流域芨芨草草地的土壤大孔隙特征,以青海湖流域芨芨草草地为研究对象,在研究区芨芨草斑块处和芨芨草斑块间分别采集原状土柱,每块样地选取3个重复样品,通过对样品进行CT扫描并利用Fiji软件解译的方法分析土壤孔隙的结构特征差异。结果表明:芨芨草斑块土壤平均大孔隙数量、不同深度大孔隙数量、平均大孔隙度以及不同深度大孔隙度均大于芨芨草斑块间土壤。芨芨草斑块土壤大孔隙平均数量是芨芨草斑块之间的2.8倍,平均大孔隙度是芨芨草斑块间的12.1倍,芨芨草斑块的土壤大孔隙度随土壤深度增加呈先增加后减少的趋势,斑块间的大孔隙度呈递减趋势。     

黄土与古土壤性质对坡面土生扭口藓分布的影响

在杨凌营盘的黄土-古土壤坡面上,出露黄土的层位生长有较好的土生扭口藓,而出露古土壤的层位少有土生扭口藓分布,采样分析黄土与古土壤的物理性质和营养元素的含量,并进行室内培养实验。结果表明：古土壤的细颗粒（≤0.02 mm）含量高于黄土的;古土壤的速效K、速效Mn、速效Fe和有机质的含量高于黄土的;古土壤的CaCO3含量和速效P含量低于黄土的。在2个月的培养实验中,并未发现4个样品的生长状况出现显著差异。因此,黄土与古土壤营养元素的差异不是导致土生扭口藓空间分异的直接原因。由于古土壤粘粒含量较高,其表层更容易形成结皮,而且古土壤团聚体之间的粘合力较弱,在坡度约65°的坡面上,结皮在重力作用下脱落,而少有土生扭口藓分布。CaCO3含量与土生扭口藓分布的关联性还有待进一步研究。     

重要环境与气候变化事件:深时古土壤的记录与响应

古土壤蕴含着其形成时期的表生环境特征,是研究过去环境变化的重要地质记录。受长期埋藏与成岩作用影响,深时古土壤形态特征与现代土壤存在差别,但仍保留明显区别于相邻岩层的土壤发生学特征。土壤发生层、根系痕迹、新生体、微形态等特征有助于辨识古土壤,而古土壤元素地球化学、成壤碳酸盐C、O同位素等是判断古土壤发育强度和重建古环境与古气候的重要方法。深时古土壤记录了前寒武纪大气组成与生物演变、泥盆纪乔木出现、二叠纪末的气候突变、白垩纪大气CO2波动、早始新世的高热气候及晚新生代高原隆升等重要环境与气候变化事件,在地球表层系统的"深时研究计划"中发挥着重要作用。目前古土壤学在埋藏与成岩作用影响、环境替代指标、古环境重建模型、时间分辨率等方面有待深入研究。     

基于CT图像的土壤孔隙结构三维重建及水力学性质预测

为了更好地了解土壤孔隙结构对水分运动过程的影响机制,该文利用黄淮海平原原状潮土CT扫描图像,通过数字图像分析和计算机重建技术对孔隙结构进行三维重建,根据图像分析获得的孔隙大小分布和连通性等形态学参数建立了用于描述孔隙尺度结构特征对水分运动影响机制的网络模型,据此预测了样本尺度（样本体积为385.84 cm3）的土壤水力学性质。结果表明,模型预测的水力学性质和实测值基本吻合,变化趋势基本一致,二者的决定系数达0.94以上。结果表明相关网络模型可以较好地模拟孔隙尺度的水分运动过程,可用于预测土壤的非饱和水力学性质。     

基于CT扫描的斜坡非饱和带土体大孔隙定量化研究和三维重建

[目的]系统开展植被发育斜坡非饱和带土体中大孔隙定量化和三维重建技术研究,为水分沿大孔隙迅速运移研究提供可靠理论依据,对于降雨型滑坡研究具有基础性意义。[方法]采用CT技术对云南省昭通市盘河乡头寨滑坡滑源区左侧斜坡区两个尺寸为25cm×25cm×50cm的大尺度土柱进行扫描,得到一系列平面和纵向CT切片图像。图像处理并计算得到了土柱中大孔隙随深度的变化情况以及3种物质(砾石、土体基质和大孔隙)的CT值范围;借助VolView 3.4体可视化交互系统实现了三维大孔隙通道系统的重组,研究其在空间内的连通性、分支性和复杂性。[结果]包括根系通道、动物通道、干缩裂缝及团聚体间的结构性孔隙广泛发育于非饱和带土体中,且大孔隙分布异质性明显,波动变异较大,随着深度的增加大孔隙呈逐渐减小的趋势。三维重组清晰可见土柱内含有较多独立分布的大孔隙通道,它们具有较好的连通性。[结论]CT扫描技术作为非破坏性获得技术在斜坡非饱和土体大孔隙定量化和三维重建研究中应用是可行的。     

Characterization of Micro-Scale Pore Structure and Permeability Simulation of Peat Soil Based on 2D/3D X-ray Computed Tomography Images

Eurasian Soil Science - Understanding peatland hydrological processes and phenomena is critical for peatland management. Peat soils have a complex pore structure that affects hydrological...     

A morphological approach to understanding preferential flow using image analysis with dye tracers and X-ray Computed Tomography

A key problem facing soil physics and hydropedology at present is some of the standard theories of water flow in soils do not fully reflect the processes at the pore scale, and thus, cannot be adequately used for prediction. As such, examination of soil structure is vital for hydropedologists. Realisation that solutes move preferentially through soil into groundwaters has meant research in this area has increased in importance. This paper describes a multi-scale approach to analyse transport mechanisms using visualisation techniques. Chloride and Brilliant Blue tracers were applied to undisturbed soil cores to examine the physical and morphological properties associated with preferential flow in a range of soil types. Following collection of serial digital images, it was possible to examine and quantify the nature of active water flow mechanisms in terms of both dye-stained pathways and spatial distribution of dye concentration, using image analysis. Preferential flow linked to water potential and soil structural discontinuity was observed in all but the coarsest textured soil which conformed to uniform flow theory. A high level of variability in flow patterns was noted between the soil types. Such information as to how a soil dynamically re-wets is key for hydropedologists involved in applications such as pollution modelling. This is especially significant when considering a wetting mechanism, such as preferential flow, that cannot be adequately described by conventional soil physics.     

陕西省泾阳南塬崩塌、滑坡地质灾害及成因分析

泾阳南塬崩塌、滑坡带是关中地区黄土台塬地质灾害的典型代表。分析了该类灾害的分布规律及形成过程,结果表明活动构造、地震、地貌、地层岩土、河流侵蚀是该区地质灾害形成的基础,人类过度扰动及灌溉是其形成的诱因。提出该类预防总体应以避让为主,局部兼以工程治理。     

昆山绰墩古土壤粒度特征及母质判别

自第四纪晚期以来,来自黄土高原的粉尘在风力作用下不断向东南扩张,在长江中下游地区形成了下蜀黄土。太湖流域的部分水稻土就是在下蜀黄土之上发育的。本文对绰墩古土壤的粒度组成特征进行了系统的研究。结果表明,绰墩古土壤<5μm粘粒、5~10μm细粉砂和10~50μm粗粉砂组分平均含量分别为22.89%、22.96%和63.52%,其中10~50μm粗粉砂组分为众数粒组。>50μm砂粒平均含量仅为5.10%。绰墩古土壤粒度组成与镇江下蜀黄土粒度组成具高度相关性(r=0.97)。根据粒度分析,我们初步认定绰墩古土壤母质为下蜀黄土。     

Assessment of the burrow system of Lumbricus terrestris, Aporrectodea giardi, and Aporrectodea caliginosa using X-ray computed tomography

Artificially packed soil columns were inoculated with individuals of different earthworm species (Lumbricus terrestris, Aporrectodea giardi or Aporrectodea caliginosa) and placed under controlled conditions in the laboratory. At the end of the incubation period, which lasted 8 months, three-dimensional reconstructions of the burrow system of each species were obtained using X-ray computed tomography. The particular features of the three burrow systems and the differences between them are discussed in terms of density, orientation and distribution of the burrows and the complexity of the network in relation to variations in soil depth and soil density. Received: 5 February 1997     

Characterization of the burrow system of the earthworms Lumbricus terrestris and Aporrectodea giardi using X-ray computed tomography and image analysis

 The burrow systems of two earthworm species (Lumbricus terrestris and Aporrectodea giardi) were studied in artificially packed soil columns placed in controlled conditions in the laboratory. At the end of the incubation, which lasted 246 days, the burrow systems were characterized on the undisturbed columns using X-ray computed tomography. This method provided a set of digitized images corresponding to horizontal 3-mm-thick sections. The following parameters were measured using image analysis on each section: number of biopores, their volume, and their individual orientation calculated using an elliptical model of the earthworm channel. The profiles of these parameters through the columns showed that the burrow systems of L. terrestris and A. giardi, which are both anecic species, were very different in terms of total volume, number of burrows, burrow orientation and extension with soil depth. These results led us to conclude that the burrow system of L. terrestris can be considered as a permanent structure whereas that of A. giardi is closer to the burrow system of endogeic species. Received: 12 June 1998     

泾河下游南岸台塬边坡稳定性与滑坡诱因分析

泾河下游南岸台塬边坡的滑坡灾害严重，本文中分析了滑坡的特征，通过计算边坡稳定性系数对台塬边坡进行了分类，对具有突发性和短期可变性的滑坡触发因素进行了分析，提出了滑坡治理的方法。研究结果表明，泾河下游南岸台塬边坡临界平衡边坡和不稳定边坡占80．8％，分布在西段和中段。滑坡发生的概率为多水年〉平水年〉少水年；年内夏雨集中的7月和秋雨集中的9月是易于发生滑坡的月份。灌溉期间的滑坡占68．8％，冬季发生的滑坡主要与灌溉有关。台塬区地下水位上升是诱发滑坡的根本原因，当地下水位上升与古土壤层重合时极易诱发滑坡。台塬区应根据地下水量平衡额定灌排量，使地下水位逐步下降至第五古土壤层之下是治理滑坡的根本之计。     

Compaction effects on soil macropore geometry and related parameters for an arable field

Soil compaction decreases soil pores are important for root growth as well as infiltration of water and nutrients. A study was conducted to evaluate the effects of soil compaction on macropore parameters measured using X-ray computed tomography (CT). Macropore parameters included number of pores, number of macropores (> 1000 μm diam.), number of coarse mesopores (200 to 1000 μm diam.), porosity, macroporosity, coarse mesoporosity, area of largest pore, pore circularity, and fractal dimension of macroporosity. A field experiment was conducted on Mexico silt loam (fine, smectitic, mesic Vertic Epiaqualfs) with field treatments including four replicates of uniformly Compacted (C) and Non-Compacted (NC) plots arranged in a randomized complete block design. Soil cores (76.2 mm diam. by 76.2 mm long) were removed from three selected depths (0 to 10 cm, 10 to 20 cm, and 20 to 30 cm). Cores were scanned using a medical X-ray CT scanner with four scans taken in each sample at 15 mm spacing starting at 25 mm from the core surface. Images were analyzed using Image-J software. The C treatment was found to increase bulk density by 8% (1.34 to 1.45 g cm⁻³) and decrease saturated hydraulic conductivity by 69% (47.1 to 14.6 cm hr^− 1). CT-measured number of pores decreased by 71%, number of macropores by 69%, and coarse mesopores by 75% with the C treatment used in the study. Compaction was also found to significantly decrease CT-measured porosity and macroporosity by 64%. Differences between treatments for the parameters were most pronounced in the upper 10 cm; differences between treatments were not significant below 20 cm. A regression equation with CT-measured macroporosity, area of largest pore and porosity explained most of the variability in saturated hydraulic conductivity (R² = 0.79). Efforts should be made to minimize soil compaction due to its harmful effects on soil pores and subsequent challenges for plant root growth and enhanced runoff of water and nutrients.     

五陵塬边坡侵蚀地貌发育及其影响因素

基于前人研究成果和对陕西省关中平原中部五陵塬边坡侵蚀地貌大量的实地考察,应用遥感卫星图像等信息资料,对五陵塬南、北缘侵蚀沟谷和黄土滑塌的发育状况进行考察和分析。研究表明,五陵塬南缘发育的河流高阶地前坎(高差8~30m的黄土崖)为窑洞聚落带,受坡面径流作用发育侵蚀沟谷和黄土坍塌;该塬边黄土窑洞带侵蚀沟谷的发育状况表现为东段密度较小,规模较大,西段反之。北缘河流高阶地前坎(高差30~90m的黄土崖)西段主要发育"群发性"黄土滑塌。东段侵蚀沟谷数量少,长度较大。五陵塬边坡侵蚀地貌的发育,主要受地质构造、地形条件、新构造运动、黄土岩性和结构、大气降水与农田灌溉以及人类活动等因素影响,并会对五陵塬周边人类居住安全,边坡水土流失,塬面文物古迹保护和西咸新区发展建设产生负面影响效应。