应用“TM”卫星磁带编制森林分布图的研究

进行森林资源监测,及时准确的掌握森林资源的质量和数量及分布的现状,是加强森林资源管理的重要手段。应用遥感技术,使用新一代陆地卫星所提供的资源数据来编制中、小比例尺的森林资源分布图,对于解决大范围、大区域森林分布图的编制和快速更新问题,能收到满意的效果,具有实际意义。     

探索森林资源规划设计调查工艺改革

文章阐述了森林资源规划设计调查对林业建设与发展实际需求的紧密联系,深刻认识开展森林资源规划设计调查的重大意义,重点探索了森林资源规划设计调查优化内容、调查工艺改革、调查工艺流程和今后发展方向。     

森林经营方案编制的意义、内容及编制要点

在阐述森林经营方案编制意义的基础上,针对森林经营方案的内容及要求,提出了森林经营方案编制要点。     

湖南省森林植物园观赏竹专类园规划设计与景观营建

全面介绍了湖南省森林植物园观赏竹专类园的规划设计定位、原则和内容,重点从专类园的主题风格、规划布局、空间设计和植物配置等角度,总结专类园建设与景观营建的做法与经验,以期为观赏竹专类园的建设与城市观赏竹景观的营造提供借鉴。     

谈“天保工程”及森林管护经营的实施意义

论述了“天保工程”和森林资源管护经营的意义和作用，提出在此基础上的森林资源经营措施。     

工程化编制“森林经营方案”的探讨

根据“森林经营方案”在编制及实施过程中所面临的问题，提出将“软件工程学”的科学思想及关键技术应用于林业设计中，使林业设计向工程化的方向发展。同时，引入“森林经营方案”动态结构的概念，从宏观上给出了一个“森林经营方案”的框架结构，对“森林经营方案”的各纱进行了分类和初步分析，最后，提出了一些设想和展望。     

遂昌县“十五”森林采伐限额的编制

根据遂昌县1999年森林资源一类调查成果，利用“国家模拟计算法”软件测算年采伐量为36．82万m^3。为林业可持续发展，确认编制“十五”年采伐限额36．00万m^3，其中：主伐为25．00万m^3，低产林改造1．6万m^3，抚育间伐9．4万m^3；商品材采伐限额33．30万m^3，自用材0．90万m^3，生活烧材1.80万m^3，毛竹200．00万支。     

厦门城市森林经营方案编制几个问题的探讨

就厦门市城市森林经营方案的目标与任务、城市森林经营类型的划分、规划与布局、城市森林的培育、保护利用措施等若干问题展开探讨,旨在提高城市森林经营方案编制水平,为全省林业建设服务。     

“十二五”期间年森林采伐限额编制

从编限指导思想、编限原则、编限基本情况、限额分析、编限主要特点等方面介绍了"十二五"期间年森林采伐限额编制工作。     

浅谈二类经理调查及森林经营方案的编制与“天保”工程

介绍了二类调查及编制森林经营方案与“天保”工程的关系，提出编制经营方案要结合“天保”工程的具体措施。     

园林绿化和工业用材的优良树种--美国梧桐

美国梧桐广泛分布于北美，适应性广，尤其耐水湿。其树形优美，是良好的庭园绿化树种；生长迅速，也是重要的短周期工业用材树种。     

Structural health assessment of in situ timber: An interface between service life planning and timber engineering

Abstract

The in situ assessment of timber structures has gained considerable attention in recent years due to some unexpected failures of public buildings. The assessment of timber, however, has been used in the evaluation of historic structures for a number of years, and the methods employed have evolved from visual observation (which is still one of the most effective ways of evaluating in situ timber) to more sophisticated methods that use various physical phenomena such as stress-wave or X-ray energy attenuation. In the health assessment of timber, effects of biotic elements such as insects and fungi are of interest, which, of course, is always connected with the presence of water in wood. The structural assessment encompasses questions related to the structural integrity of in situ members and the performance of components and the system. The structural health assessment not only focuses on biotic elements but also attempts to quantify engineering properties of the material such as strength degradation, modulus of elasticity, loss of cross-section, extent of checks, and other quantitative parameters needed for subsequent evaluation of the structural system, frequently expressed as load-bearing capacity. Service life planning of a structure is a complex issue that is related not only to the materials but also the environment and the use of the structure. Assessment of the health and properties of existing timber elements yields a piece of information that is necessary but not sufficient for the service life estimate. In the evaluation of structural timber, a mere use of various assessment techniques is not sufficient and usually an involvement of disciplines such as wood anatomy, wood physics, and statistics is needed. A reliable estimate of the parameters of in situ timber requires careful planning of measurements (experiments) since the material is highly variable and any statement about the properties of an element or even the entire system must reflect the random character of the wood properties. This paper will summarize the state-of-the art methods used in the assessment of in situ timber and analyze the strengths and the weaknesses of selected methods. An attempt will be made to outline future directions in the development of in situ assessment methods.     

The potential of high-yield plantation forestry for meeting timber needs

This study examines the performance and potential of intensively managed plantation forests as a source of industrial wood, and their environmental implications. The perspective of the study is global. Although it includes the United States and parts of Europe, much of the focus is on what are called the emerging plantation regions -- countries largely in the semitropical areas of the southern hemisphere -- which have not historically been important wood producers, but are growing in importance as a result of the productivity of their planted forests. The first section of this paper documents the growing importance of plantations as a source of industrial wood since the late 1970s. The study finds that plantations from nontraditional (new) regions have been growing rapidly in size and economic importance, and, thus, have been playing an increasing role as a source of the world industrial wood. Furthermore, experience seems to suggest that plantations are playing an environmentally beneficial role in (1) reducing pressure on greater areas of natural forests and (2) generating positive environmental effects as they replace degraded marginal agricultural lands. The second section of the paper examines the likely role of plantation forests in the future, and includes an assessment of financial, political and environmental considerations. This section pays particular attention to the concerns frequently expressed by environmentalists regarding plantations. Many of the objections directed at forest plantations on environmental grounds appear to ignore the substantial beneficial role of plantations on the environment. Plantations, which are financially very attractive in many locations, offer the potential of meeting large portions of the world industrial wood needs even while reducing substantially the disturbances on large areas of natural forests. This is possible because the very high productivity of plantation forests requires less area to produce industrial wood.     

The impact of landscape design planning on the timber production and financial outputs of a forest plantation in Ireland

Significant expansion has occurred in Ireland's forest estate since the 1950s. However, the design of the monocultural plantations established in the 1950s and 60s is now considered insensitive to local landscapes and re-design intervention and transformation is needed to improve integration into the environment. This case study was carried out in Laracus forest, Co. Donegal. The rotation of all stands in this 581-ha property has reached the final production phase, with coupes scheduled for clearfelling from 2003 to 2015. The implications of forest re-design for both the volume production in the current rotation and the financial return of the current and subsequent rotations were examined. Results indicated a volume loss due to design planning for the current rotation of 5.6% compared to the volume produced under the standard regime. In financial terms, this represents a loss of 4.6%. For the subsequent rotation, a significant financial gain of 22% in net present value was achieved as a result of redesigning the plantation. The overall financial out-turn for the property, when both the current and subsequent rotations were considered, was a 3.4% lower net present value for the design plan than for the standard regime. This result represents a lower impact of design planning in Laracus than most other forest restructuring studies have reported.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

Rotational position of curved saw logs and warp of the sawn timber

With the development of scanning technology in sawmills, it is possible to optimise log rotational position when sawing. However, choosing a different rotational position than horns down might be detrimental for the board shape after drying, especially for curved logs. Thus, there is a need to investigate at what level of log curve it is possible to freely rotate logs without causing board warp. This study was carried out through a test sawing that was conducted at a sawmill situated in the middle of Sweden. The tests were made on 177 Norway spruce logs, with varying amount of curve. Half of the logs were sawn in the horns-down position, half were sawn rotated perpendicular to horns down. Log shape and warp of the dried boards were measured. The results indicated a relationship between board spring, log curve and choice of rotational position. Furthermore, board bow was related to log curve but not rotational position. It can be concluded that for straight logs, with a bow height of less than 15 mm, an unconventional rotational position does not cause excess spring in the boards. Bow and twist are not affected by the rotational position at all.     

Theoretical and experimental deflections of glued laminated timber beams made from a tropical hardwood

Abstract

Nondestructive testing (NDT) can play an important role in improving the quality and reliability of tropical hardwood as an engineering material. By means of these methods, the stiffness of the material can be determined and the information used to improve its structural performance. Although, it is a usual approach for qualifying the material used to manufacture engineered wood products made mainly from softwoods, it is not so common for tropical hardwoods. Additionally, the lack of information regarding properties of glulam beam made from these kinds of wood is evident. In this context, the paper aimed at evaluating the theoretical and experimental deflection of glulam beams made from the Brazilian hardwood louro-vermelho (Sextonia rubra). Initially, the stiffness of each lamina was determined nondestructively using transverse vibration method (E _dtv), which has been demonstrated to be the most suitable method for this wood species. Then, ten 5-lamina glulam beams were assembled according to descending lamina E _dtv values. The experimental evaluation was performed using a four-point bending schedule. In general, the theoretical values of deflection were 2% higher than the experimental ones. The transverse vibration showed to be a suitable method to both measure lamina stiffness and predict glulam beam deflection.     

长沙市景观生态规划设计初探

根据城市景观生态规划设计的内涵、原则和方法,分析了长沙城市景观生态规划设计存在的主要问题,探讨了改善的思路和措施。     

木质颗粒连续生产工艺和设备选型

阐述了木质颗粒连续生产工艺、影响木质颗粒质量的主要因素及生产设备的选型,可为木质颗粒生产企业提供参考。     

便携式木材绞盘机新型卷筒离合器设计

在利用便携式木材绞盘机进行木材生产试验过程中,发现卷筒离合器在分离与接合过程中易出现卡阻现象,从而影响集材生产效率。在对牙嵌式离合器结构进行受力分析和卡阻原因分析的基础上,基于Solid Works的建模分析设计方法,设计了一种新型多孔旋转圆柱式卷筒离合器,该方法有效缩短了新型卷筒离合器的设计周期。新型卷筒离合器采用圆柱销与圆孔的嵌合,代替牙嵌式离合器牙嵌轴与牙嵌套的嵌合,同等试验条件下,旋转柱销式卷筒离合器平均分离时间分别比柱销式卷筒离合器节省3.71 s、比牙嵌式卷筒离合器节省8 s,改善了便携式木材绞盘机卡阻后离合器分离困难的现象,节约了离合器分离时间,从而有效提高了便携式木材绞盘机在集材作业中的生产效率。