探地雷达在探测土壤含水量方面的研究进展

指出了探地雷达(Ground Penetrating Radar,GPR)是一种新型的、无损的能够快速测定土壤含水量的一种方法。GPR作为一种中大尺度的土壤含水量探测方法,在探测土壤的含水量有着广泛的应用前景。对大量国内外利用探地雷达探测土壤含水量的研究方法进行了汇总分析,目前利用探地雷达探测土壤含水量的方法主要包括4种:反射波法、地面波法、地表反射系数法、钻孔雷达法,其中根据反射波法是比较常用的。通过概述国内外利用探地雷达来探测土壤含水量的不同方法及研究现状,对这4种利用探地雷达探测土壤含水量的方法原理及其优缺点进行了详细地阐述,最后通过大量相关研究的结果,说明利用探地雷达在探测土壤含水量方面的方法是可行的,为利用探地雷达探测土壤含水量提供理论基础。     

基于探地雷达的根系探测对土壤含水量的响应

在探地雷达对地下根系进行探测和识别的过程中,土壤含水量是影响根系探测效果的一个极为重要的因素.本文在2种质地土壤(砂质壤土和粘土)不同水分含量下,通过探地雷达对根进行模拟试验,测定了2种质地土壤的电磁波波速,同时测试了根的探测效果.结果表明:土壤含水量是影响电磁波波速的主要因素,电磁波波速不受天线频率的影响,但随着土壤...     

立地环境改造对古树根系分布特征的影响——以44011111322000296号朴树为例

古树健康与根系生长联系密切,改善根系生长环境是衰弱古树复壮的重要技术措施。研究以广州市白云区44011111322000296号朴树Celtis sinensis古树为研究对象,研究立地环境改造对朴树古树生长的影响,并采用探地雷达研究古树根系分布特征的变化。结果显示:与改造第1天相比,第300、600天时朴树古树叶片全N、全P、全K含量显著增加(P0.05)。随着改造时间的延长,朴树古树根系数量和密度均呈现明显增加的趋势,第130天后距离茎干5.0 m处根系数量最多,根系水平延伸范围增大;第130天时95.69%根系数量集中在深度20～41 cm之间,至第300天时93.32%的根系数量集中在深度41 cm以下,根系深层延伸趋势明显。研究表明,立地环境改造能够促进44011111322000296号朴树古树长势恢复,尤其是促进根系生长和叶片养分积累。     

面向探地雷达应用的活立木木材介电常数受主要应用条件的影响

[目的]目前,探地雷达常被应用于活立木缺陷、健康水平以及根系分布等的检测,检测系统中通常默认介电常数为固定值,但经初步研究发现,活立木的介电常数受环境及自身性质等的影响并不是一成不变的,在检测中使用默认的介电常数值会降低检测的准确性.因此,探究在不同应用条件下的活立木木材介电常数变化,建立各因素与介电常数值相关模型可为...     

植物根系生物学研究进展

根系生物学是近十几年来兴起的一门专门研究植物根系的前沿学科,研究领域涉及形态学、生理学、发育生物学、分子生物学、遗传学等多个学科。根系生物学是重要的生态和农业指标,对于保护和利用植物资源、改良植物遗传品质和提高植物生产力具有重要的指导作用。文中从根系构型、根系生长发育与环境、根际、根系解剖结构以及根系遗传改良等方面总结归纳植物根系生物学的研究进展,阐明根系生物学的研究意义,在探讨当前根系生物学研究存在问题的基础上提出今后研究建议。     

植物根系分布与根际微生态研究方法概述

根系是植物在地下所有根的总合,也是植物吸收、运输和储藏营养物质的重要器官;根际微生态是指受植物根系、土壤微生物以及根系周围各个因子相互作用的土壤区域.根系的分布和走向会对根际微生态产生不可忽视的影响,同样根际微生态也会影响植物根系分布.本文主要对植物根系分布与根际微生态的研究方法进行介绍,解决植物根系分布与根际微生态方...     

杨树根系对氮磷养分的吸收动力学研究

根系养分离子吸收动力学研究在植物的矿质营养中占有重要地位。根系养分吸收动力学的研究为阐明养分吸收特性、鉴定和筛选养分吸收高效的基因型提供了有利的手段。许多研究结果表明根系吸收动力学特性是植物效率差异的一个重要因素，不同基因型植物根系对营养离子的吸收特性具有较大的差异。植物根系吸收营养离子的动力学特性的特征主要是通过吸收动力学参数来描述的。     

深根植物对埋地天然气输气管沥青涂层的影响

本文通过对四川、重庆两地所管辖区域的天燃气输气管线上24个树种及其根系的调查,并对其109个不同深度的探坑数据的统计分析认为:输气管的埋地深度大于100cm,植物根系对其影响较小;深度在100cm内时,影响较大。植物距管线越近,其影响危害越大。不同土壤的埋地深度的影响为沙土>壤土>粘土。     

提高植物磷高效利用能力方法的研究进展

磷是植物生长所必需的营养元素之一。但大多数土壤具有全磷含量高,有效磷含量较低的特点,难以满足植物生长的需要。而提高植物对土壤中磷素的吸收利用能力是解决土壤有效磷供应不足的有效途径。根系是植物吸收矿质养分的主要器官,其特性决定着植物对土壤磷的吸收和利用效率,因此分析根系及根际分泌物对土壤磷素的响应机制是提高作物磷效率的基础。同时通过外源添加土壤磷活化剂以提高我国磷肥利用率,也是促进植物磷高效利用的有效方法。但目前有关提高植物对磷的高效利用的研究主要集中于外源添加磷活化剂,根系形态结构的变化、根系与根际微生物互作方面,而在土壤系统中各个要素的相互作用关系极为复杂,因此,提出了在未来的研究中也不应局限于单一因素的研究发展,磷高效利用机理及方法还需进一步研究完善。     

关于植物根系形态分布研究进展与新方法探讨

根系是影响植物生长的重要组成部分,同时根系对浅层边坡加固具有重要作用。根系结构是一个具有自相似特征的非规整复杂形体,欧氏几何中难以定量测量,将分形理论应用于根系结构中,能很好的定量描述根系结构形态。本文分析植物根系护坡和分形理论在植物根系中应用这两个领域国内外研究成果。在此基础上提出,基于L-系统理论构建植物根系形态模型,利用有限元软件数值模拟根系模型与土共同作用对边坡稳定性影响的思路。     

基于雷达遥感技术的土栖白蚁探测

应用一种非破坏性的地球物理探测技术——雷达遥感技术,探测土栖白蚁巢穴.通过对金属管和蚁巢的掩埋模拟探测试验,测定地下目标影像尺寸,建立目标-影像尺寸线性关系模型,构建土栖白蚁蚁巢的二维和三维影像图;通过林地实地探测,获取不同目标反射的影像数据,有代表性地开挖验证,初步获得金属、树根、空洞和蚁巢4类地下主要目标影像特征;蚁巢尺寸的雷达遥感测量数据综合误差率为1.93％.雷达地下遥感探测技术是土栖白蚁监测和防灾减灾的有效辅助工具.     

Root imaging from ground penetrating radar data by CPSO-OMP compressed sensing

As the amount of data produced by ground penetrating radar (GPR) for roots is large, the transmission and the storage of data consumes great resources. To alleviate this problem, we propose here a root imaging algorithm using chaotic particle swarm optimal (CPSO) compressed sensing based on GPR data according to the sparsity of root space. Radar data are decomposed, observed, measured and represented in sparse manner, so roots image can be reconstructed with limited data. Firstly, radar signal measurement and sparse representation are implemented, and the solution space is established by wavelet basis and Gauss random matrix; secondly, the matching function is considered as the fitness function, and the best fitness value is found by a PSO algorithm; then, a chaotic search was used to obtain the global optimal operator; finally, the root image is reconstructed by the optimal operators. A-scan data, B-scan data, and complex data from American GSSI GPR is used, respectively, in the experimental test. For B-scan data, the computation time was reduced 60 % and PSNR was improved 5.539 dB; for actual root data imaging, the reconstruction PSNR was 26.300 dB, and total computation time was only 67.210 s. The CPSO-OMP algorithm overcomes the problem of local optimum trapping and comprehensively enhances the precision during reconstruction.     

Detection of tree roots and determination of root diameters by ground penetrating radar under optimal conditions

A tree's root system accounts for between 10 and 65% of its total biomass, yet our understanding of the factors that cause this proportion to vary is limited because of the difficulty encountered when studying tree root systems. There is a need to develop new sampling and measuring techniques for tree root systems. Ground penetrating radar (GPR) offers the potential for direct nondestructive measurements of tree root biomass and root distributions to be made. We tested the ability of GPR, with 500 MHz, 800 MHz and 1 GHz antennas, to detect tree roots and determine root size by burying roots in a 32 m3 pit containing damp sand. Within this test bed, tree roots were buried in two configurations: (1) roots of various diameters (1-10 cm) were buried at a single depth (50 cm); and (2) roots of similar diameter (about 5 cm) were buried at various depths (15-155 cm). Radar antennas were drawn along transects perpendicular to the buried roots. Radar profile normalization, filtration and migration were undertaken based on standard algorithms. All antennas produced characteristic reflection hyperbolas on the radar profiles allowing visual identification of most root locations. The 800 MHz antenna resulted in the clearest radar profiles. An unsupervised, maximum-convexity migration algorithm was used to focus information contained in the hyperbolas back to a point. This resulted in a significant gain in clarity with roots appearing as discrete shapes, thereby reducing confusion due to overlapping of hyperbolas when many roots are detected. More importantly, parameters extracted from the resultant waveform through the center of a root correlated well with root diameter for the 500 MHz antenna, but not for the other two antennas. A multiple regression model based on the extracted parameters was calibrated on half of the data (R2 = 0.89) and produced good predictions when tested on the remaining data. Root diameters were predicted with a root mean squared error of 0.6 cm, allowing detection and quantification of roots as small as 1 cm in diameter. An advantage of this processing technique is that it produces results independently of signal strength. These waveform parameters represent a major advance in the processing of GPR profiles for estimating root diameters. We conclude that enhanced data analysis routines combined with improvements in GPR hardware design could make GPR a valuable tool for studying tree root systems.     

断根对滇润楠生长发育的影响

切断侧根会对滇润楠苗木地上部分的生长产生负影响而有利于促进新根的萌发,其影响与断根的强度有关.采用一次全部切断侧根并在切口喷上生根粉,40天后有新根生出,3个月每株萌发的新根平均达222条、≥5 cm侧根数平均为74.8条、侧根深度28 cm、最长侧根13.6 cm,新根已基本发出完毕,因此3个月后就可以移栽而能保证成活率.     

Mapping tree root systems with ground-penetrating radar

A ground-penetrating radar (GPR) technique was used to study the three-dimensional distribution of root systems of large (DBH = 14 to 35 cm) oak trees (Quercus petraea (Mattusch.) Liebl.) in relatively dry, luvisoil on loamy deluvium and weathered granodiorite. We used a pulse EKKO 1000 GPR system, a profile grid of 0.25 x 0.25 meters, at 0.05 m intervals, and a signal frequency of 450 MHz, to assure resolution of about 3 cm in both directions (further increases in resolution up to 1 cm are possible with the system). Coarse root density was 6.5 m m(-2) of stand area and 3.3 m m(-3) of soil volume. Maximum rooting depth of the experimental oaks was 2 m, and the root ground plan was significantly larger (about 1.5 times) than the crown ground plan. Based on earlier studies of Quercus robur L. from floodplain forests, where the extent of the root systems was much smaller (root ground plan:crown ground plan ratio of 0.6), we conclude that the high root ground plan:crown ground plan ratio indicates less favorable conditions of water supply at the experimental site than in the floodplain forest. The ground-penetrating radar system is noninvasive and allows relatively rapid and repeated measurements of the distribution of coarse root systems of trees.     

Detecting defects in conifers with ground penetrating radar: applications and challenges

Our objective was to test ground penetrating radar (GPR) to non‐destructively estimate decay volumes in living coniferous trees. GPR is geophysical tool which uses an antenna to propagate short bursts of electromagnetic energy in solid materials and measure the two‐way travel time and amplitude of reflected signals. We compared estimates of bole decay from data collected with a SIR 3000 GPR system equipped with a 900 MHz antenna to measurements of decay from stem cross sections and increment cores for three conifer species (Pseudotsuga menziesii, Thuja plicata and Tsuga heterophylla). We found that near‐surface decay, air‐filled voids and desiccated boles had unique electromagnetic signatures, which could be separated from other defects. GPR successfully estimated the percent area of air‐filled cavities and was not significantly different than results from destructive sampling. However, separation of incipient to severe decay from benign reflectors (e.g. moisture gradient between sapwood and heartwood) in conifers was much less diagnostic than with angiosperms. A limited assessment of Acer saccharum showed that GPR has potential to detect defects in angiosperms; however, more research is needed to outline the full range of detectable defects. Based on the trees in this study, the potential for GPR to detect decay‐related defects in conifers seems limited. Despite problems detecting decay, reflections originating from the sapwood : heartwood boundary may prove useful to determine thickness of functional sapwood in conifers, but accurate quantification will require further technical development.     

木麻黄苗期最佳固氮基因型组合体研究

在野外苗圃中，对放线菌Ｆ２８７与不同基因型苗（１４个种源的普通木麻黄和１０个种源和家系的山地木麻黄）组合的研究表明，在生长和生物量指标上，参试苗木的基因型间存在着显著或极显著差异，且按种与未接种处理间也存在着显著或极显著差异；接种后形成的２４固氮基因型组合体的各指标增量平均值变化非常大；根瘤数为０．３－８．９个／株；苗高为－２．１－４０．３ｃｍ；地径为－０．０４－０．１８ｃｍ；地上生物量为－０．２     

Modification of root IAA concentrations,tree growth,and survival by application of plant growth regulating substances to container-grown conifers

Tree survival after planting ispartially a function of the tree's capacity toproduce new roots. In a field trial we assessedthe potential to modify the IAA concentrationin roots, root growth responses, and plantsurvival by root application of plant growthregulators (PGRs) such as IBA, NAA, andethylene, or alginate, a moisture retentionmaterial. Container-grown Douglas-fir,Englemann spruce, and lodgepole pine werelifted before and during prescribed liftingwindows and treated with Stim-root®, Ethrel®,Hormogel®, or alginate before or aftercold-storage, then planted in a clearcut.Lifting trees outside of the prescribed liftingwindow decreased IAA concentrations in roots ofDouglas-fir, Englemann spruce, and lodgepolepine. Treating plants with different PGRs aftercold storage increased root IAA concentrationsand root growth after planting compared totreating plants prior to cold storage. Rootgrowth and above ground plant growth andsurvival were well correlated to IAAconcentrations in roots of Douglas-fir andEnglemann spruce. IAA concentrations in rootsof lodgepole pine correlated with root growth,but did not correlate with survival. A costanalysis of treatment effects on growth andsurvival showed that certain post-cold storagePGR treatments can decrease the cost necessaryto attain target stocking and increase the sizeof the trees. Our results suggest thatapplication of PGRs or other root-promotingmaterials to tree roots before planting has thepotential to be a cost-beneficial method forincreasing root growth and tree survival.