杂种落叶松大径材优良家系选择

以材积生长量为主要指标,对27年生杂种落叶松进行优良家系初步选择,并初步探讨了树高、胸径、中央直径及其相互作用对材积生长量的影响,进而找出影响材积生长的主要因子。研究表明,中央直径是影响材积的主要性状,性状对材积的影响依次为中央直径〉胸径〉树高。胸径与中央直径的相关较紧密,而胸径与树高、中央直径与树高的相关不同家系表现各异。     

大径材杂种落叶松优良家系选择

为选择适宜大径材培育的杂种落叶松优良家系,以40年生全同胞子代测定林31个家系为研究对象,对其生长性状、干形性状、遗传力及遗传增益进行了测定.结果 表明:生长性状单株遗传力整体高于干形性状,树高单株遗传力平均值超过0.5,胸径平均值超过0.4,中央直径平均值超过0.3,材积的平均值超过0.5.胸径和材积的相关系数为0....     

华北落叶松人工林大径材培育综述

我国大径材原料供需形势严峻,培育华北落叶松人工林大径材可以缓解用材紧张现状。笔者在借鉴他人对桉树、杉木大径材培育研究的基础上,从优质种源、立地条件和栽培技术3方面综述了华北落叶松人工林大径材培育技术,以期为华北落叶松人工林大径材培育提供理论参考。     

落叶松人工林大径材培育森林抚育技术

按照落叶松大径材培育模式,针对孟家岗林场68林班13小班的落叶松人工林生长状况,根据林分直径分布模型算出间伐时林分的直径分布,按照下层抚育间伐的方法确定间伐强度,科学调整林分结构,促进林分健康生长。     

日本落叶松大径材培育技术的研究

通过对26年生日本落叶松大径材的培育试验研究,结果表明:以保留密度600株·hm-2和750株·hm-2的效果最佳,伐后5年大径木可增加50%左右,是对照区的3倍,小径木下降70%左右。主伐时产量预测为:600株·hm-2的林分材积416.94 m3·hm-2,产值91.96万元·hm-2;750株·hm-2的林分材积453.28 m3·hm-2,产值93.62万元·hm-2。     

长白落叶松大径材定向培育技术的研究

对长白落叶松大径材定向培育的试验表明:25 a生长白落叶松间伐后8 a的生长变化以525株.hm-26、00株.hm-2的保留密度生长量最大,胸径年生长量在0.5-0.6 cm以上,年材积平均生长量在7.6 m3.hm-2以上;培育大径材的初植密度以2 500株.hm-2或3 300株.hm-2为宜。     

长白落叶松大径材培育试验初报

通过在辽宁省新宾县陡岭林场进行的长白落叶松不同密度生长对比试验，结果表明，保留密度为５２５￣６００株／ｈｍ＾２的林分，胸径和材积生长量最大，建议在土壤肥沃、长白吕松纯林面积大、采伐周期集中的国有林场进行长白落叶松大径材培育，这对于提高单位面积木材产量、调整林龄结构、满足市场对大径材的需要是非常有效的技术措施。     

落叶松大径材兼顾林下经济植物培育模式研究

以清原满族自治县为例,简要介绍落叶松大径材与林下经济植物复层模式、营林措施及主要培育模式,以构建稳定的森林生态系统并为农村经济发展开辟新路子。     

落叶松大径材培育林分伐前更新红松关键技术

该文通过对辽宁东部落叶松大径材培育林分分析，提出了伐前更新红松的造林模式、异砧嫁接、病虫害防治和上层木采伐的技术和管理措施，以期为辽宁东部落叶松大径材培育林分的更新提供参考。     

落叶松人工林大中径材优化经营模式

以黑龙江省落叶松人工林为研究对象,利用获取的调查数据,综合林分生长模型、动态规划模型等,以净现值和内部收益率为经济评价方法确定出落叶松大、中径材优化经营模式。研究结果表明:16地位级适合培育中径材,不同初植密度林分间伐3次就可以进行主伐;18地位级以培育大径材为主,密度4 400株/hm2的林分需要间伐5次,而密度3 300株/hm2的间伐4次就可以获得目的材种;20地位级也主要培育大径材,经过间伐4⁵次后,将获得最大的经济效益。全部优化经营模式内部收益率均在15%以上。本研究为提高落叶松人工林经营水平奠定理论基础。     

Modeling wood pole failure

Summary In part 1 of this series, a three-dimensional, structural analysis, finite element program has been developed to predict the stress distribution in wood poles with and without spiral grain and variable material properties. This program serves as a basis for a model to predict the strength and failure location in full-size wood poles. Fundamental to this model is the ability to quantify the effects of key material and geometric properties of the pole. This paper deals with the enhancement of the program to quantify the effect of knots and their associated cross grain on the stress distribution of wood poles. The technique is based on the theoretical behavior of laminar fluid flow around an elliptical obstruction. The flow-grain analogy was employed to develop empirical relationships between knot diameter and pertinent variables (grain deviation angle near the knot and area of influence of the knot). Prior to the development of the empirical relationships, a study was conducted to determine the size and distribution of knots in Douglas-fir and western redcedar poles.The validity of the technique to describe knot behavior is reflected in the ability of the finite element model to predict the strength and failure location of wood poles. The results suggested that the flow-grain analogy is a rational mechanism to quantify the fiber orientation near a knot. Furthermore, this technique could have meaningful implication in improving visual grading methods for wood poles.The authors would like to recognize the contributions of Engineering Data Management, Inc. of Ft. Collins, Colorado for their contribution of test materials and facilities for this study.     

Modeling wood pole failure

Summary This is the first of two papers designed to describe the most recent efforts in using contemporary technology to predict strength and failure location in wood poles. In this report, a three-dimensional finite element model is presented which was developed to provide a rational stress analysis tool for wood poles. Due to practical considerations, only critical pole segments were subjected to stress analyses. Twelve-inch (30.5 cm) segments were selected for analysis which contained knots or knot clusters deemed consequential.The linear elastic model assumes small-deflection theory, and exploits linear strain, 15-node wedge and 20-node parallelepiped, isoparametric finite elements. Element geometry was selected to reflect knot size distribution found in full-size wood poles used in North America. Boundary conditions represented both applied loading and support considerations.Model verification studies were conducted on poles with isotropic (steel) and anisotropic (wood) material properties with and without spiral grain and variable longitudinal elastic properties along the pole radius. The results showed excellent agreement between theoretical and numerically-predicted pole stresses. The effect of boundary conditions on predicted stress distribution was defined, and the element geometry was appropriately modified. The developed model proved to be a rational basis for a more enhanced version to predict the mechanical behavior of wood poles with several inherent growth characteristics.     

Isotropy at the center of a cylindrical wood pole

Summary This paper studies the title problem on the basis of the consideration of the generalized plane deformation of a cylindrically aeolotropic body.

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Zusammenfassung Die vorliegende Studie beschäftigt sich mit der Frage der Isotropie im Zentrum einer geraden zylindrischen Säule aus Holz. Zugrundegelegt ist die Annahme der grundsätzlich ebenen Verformung eines zylindrischen anisotropen Körpers.

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The authors wish to express their sincere appreciation to Dr. E. R. Mark, Department of Forestry, University of Kentucky, Lexington, Kentucky. This problem was encountered in some of his research project under the sponsorship of the McIntire-Stennis Cooperative Research Program of the U.S. Department of Agriculture.     

Scottish farmers' intentions to afforest land in the context of farm diversification

Increasing woodland area in the United Kingdom is strongly supported in policies, but there is evidence of low rates of new planting, infrequent uptake of farm forestry, and negative attitudes to woodland among farmers. Additionally, there is a wider context of increasing farm diversification, and a need for greater understanding of farmers' attitudes and behaviour related to afforestation. This paper uses a representative survey of Scottish farmers (survey year: 2013, respondents used in analysis: 1735) to compare farmers who intended to expand forestry in future and farmers with alternative combinations of intended and past behaviour in relation to forestry. Overall, we find that certain characteristics: already operating forestry, reporting types of non-farming activities, involvement in environmental schemes, having a high education level, having a relatively high number of employees, and being relatively recent entrants to holdings, were more frequently found among farmers intending to increase forestry in future than farmers described as ‘non-increasers’ who did not intend to increase forestry and also had not expanded it in the past. Farmers with these characteristics could be a useful focus in attempts to expand woodland at larger scales, and encouraging small-scale tree planting could be an effective policy approach.     

Dynamic crushing characteristics of spruce wood under large deformations

An extensive series of large deformation crushing tests with spruce wood specimens was conducted. Material orientation, lateral constraint and loading rate were varied. Regarding material orientation, a reduction in the softening effect and the general force level was observed with a higher fiber-load angle. A comparison with characteristics gained by application of Hankinson’s formula showed discrepancies in compression strength and the beginning of the hardening effect. Lateral constraint of the specimens caused a multiaxial stress state in the specimens, which was quantified with the applied measuring method. Further, a higher force level compared to specimens without lateral constraint and significant hardening effect at large deformations resulted. Thus, the influence of a multiaxial stress state on the force level could be determined. An increase in the loading rate led to higher force levels at any displacement value and material orientation.     

人工长白落叶松优良单株母树选择技术

文章简述了长白落叶松优良母树选择的意义,优良母树选择、分级的标准、方法。     

日本落叶松全同胞子代生长性状的分析

利用20年生落叶松全同胞子代树高、胸径的观测数据,以小区平均数为据,采用Griffing配合力分析方法4的程序对生长性状的配合力分析,结果表明:树高、胸径的一般配合力均占优势,分别为79.82%、53.42%,说明日本落叶松生长性状的遗传主要受基因的加性效应所控制。采用配合力效应筛选的优良亲本为:宽10,草41,草13,永10,用其组建1.5世代种子园的改良效果为:树高、胸径、材积分别提高2.95%、9.70%、14.08%,筛选的优良杂交组合为:草13×草6、草82×永11、草82×503、永10×永8、草82×草13、草13×永11,用其建立人工控制授粉的杂交种子园的改良效果为:树高、胸径、材积分别提高8.28%、13.21%、27.60%。     

兴安落叶松汽蒸脱脂工艺

在温度为90℃和100℃条件下,对兴安落叶松厚、薄板材分别进行汽蒸脱脂处理。研究表明：处理温度为90℃,对兴安落叶松薄板材汽蒸处理1 h、3 h和5 h后,其脱脂率分别为4.64%、14.57%和15.89%,处理温度为100℃时,其脱脂率最高达到了17.88%,且汽蒸处理3 h和5 h的脱脂率差异不大;对兴安落叶松厚板材进行的脱脂处理发现其与薄板相似,但相对于薄板来说,厚板的脱脂较为困难。     

兴安落叶松中二氢槲皮素提取方法的比较

以二氢槲皮素的得率为指标,分别采用超声、微波和加热提取法（冷浸、温浸和回流等）从落叶松中提取二氢槲皮素。先后对提取溶剂的体积分数、料液比和提取次数等共性因素及提取时间和能量强度等核心因素进行考察,3类方法中微波提取得率最高,可达0.116%,回流提取的累积得率可达微波法的95.9%,而超声提取的累积得率仅能达到微波法累积得率的55.2%。规模化生产可采用体积分数60%乙醇作为提取溶剂,料液比1∶12,微波700 W提取2次,每次10 min或80℃回流提取3次,每次240 min。扫描电子显微镜观察结果表明：尽管超声对植物细胞组织破壁或变形的机械效应较强,但二氢槲皮素的得率仍较微波和回流提取法低,二氢槲皮素的溶出主要是导致热效应的贡献。     

兴安落叶松林蓄积量与海拔的关系研究

收集大兴安岭森林资源连续清查第6次复查325块样地资料,将其整理成列联表并分析,对其进行卡方检验、剩余分析、对数线性模型拟合的结果表明,兴安落叶松林分蓄积呈现低、高海拔处低,中部海拔处林分蓄积量高的特点。