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1.
Ze-Hui Jiang Xiao-Qing Wang Ben-Hua Fei Hai-Qing Ren Xing-E. Liu 《Annals of Forest Science》2007,64(8):807-814
The effect of stand density (1000 stems/ha, 500 stems/ha and 250 stems/ha) on tree growth and wood quality characteristics was studied in a 27-year-old plantation species of Populus xiaohei in China. Results indicated that stand density had significant effects on tree radial growth and crown size, and the lowest stand density produced trees with the largest stem taper. In terms of wood quality characteristics, there was no significant effect of stand density on either wood basic density or fiber length. However, significant differences were found between different stand densities for wood mechanical properties. A positive relationship between modulus of elasticity, compression strength and stand density was observed, while the highest modulus of rupture was recorded at a moderate density of 500 stems/ha. Stand density was responsible for highly significant effects on both juvenile wood and wet heartwood basal areas in individual trees, and there was an obvious tendency towards increasing juvenile wood and wet heartwood basal areas with decreasing stand density. In addition, the relationships between wood quality characteristics and tree and stand characteristics were also examined. Some wood quality characteristics, namely mechanical properties and juvenile wood and wet heartwood basal areas, were quantified successfully in relation to selected tree characteristics using a regression approach with various degrees of goodness of fit. Based on comprehensive consideration of various factors, such as wood quality, tree growth, and establishment cost, results from this study suggest that a density of 500 stems/ha is optimum for wood production. 相似文献
2.
S. C. Chafe 《Wood Science and Technology》1987,21(2):131-138
Summary The derivation of a value termed the R-ratio (the change in external wood volume during shrinkage or swelling per change in the weight of the associated volume of water) and its possible use as an indicator of dimensional stability (Chafe 1986, 1987), has led to its consideration as a potential wood quality index for the eucalypts. An analysis of R with respect to mechanical strength, durability, volumetric shrinkage, collapse and density in 38 species of eucalypts has shown a high degree of correlation and suggests that R could provide a single overall indication of timber quality.While density was more highly correlated with strength and durability than R, the R-ratio was more highly correlated with shrinkage. Also, when predictor criteria (strength, durability, shrinkage, density) were mutually adjusted in multiple regression analysis, R remained significantly correlated with each. When density was similarly regressed against shrinkage, durability and strength, the relationship was not significant for shrinkage.The observed high correlation between durability and density suggests that mass of wood substance is an important criterion in defining resistance to wood decay.The author wishes to thank Dr. W. E. Hillis, Mr. W. G. Keating, Mr. J. Ilic and Mr. E. P. Lhuede for kindly assigning wood quality rankings to the 38 species of Eucalyptus discussed herein 相似文献
3.
以9年生黑杨派无性系试验林为试材,分析了多个性状间的相关关系,结果表明,生长、干形、冠形及木材性状间均存在显著的相关关系。首次发现树高与边材宽度存在极显著的遗传正相关,表明选育树高生长快的无性系,其边材宽度将得到提高,木材性状相应得到改良;生长性状与气干密度的相关性不显著,故对生长性状的改良并不影响木材性状的表现;气干密度与其它力学性状呈显著或极显著遗传正相关,与干缩率相关不显著,这表明选择气干密度大的无性系,其力学性状会得到显著提高,而对干缩率影响不显著。这些结论对于优良无性系选择具有重要的指导意义。 相似文献
4.
材性改良研究：Ⅰ.X射线木材密度测定 总被引：6，自引：2，他引：6
利用Ｘ射线衍射（Ｄ－ｍａｘ３Ｂ型）改装成直接扫描式Ｘ射线木材密度计，可快速、高效测定木材密度组成，即木材平均密度，平均早材密度，平均晚材密度，最大木材密度，最小木材密度，木材密度梯度和木材密度的变异幅度，为材性改良提供了新手段，本文用Ｘ射线木材密度计测定１７个树种木材密度。 相似文献
5.
Factors influencing steel tool wear when milling wood 总被引：2，自引：0，他引：2
The wear of high speed steel cutting tools after milling wood of four selected wood species was studied. For the experiments wood specimens were chosen with very different silica contamination, wood density, and high temperature corrosivity (HTC) of wood towards tool material. Analyses performed show that the silica content and wood density display poor linear correlation with the cutting tools wear, while the correlation of the HTC appeared very good. The silica contamination and the HTC effects overshadow each other. Thus, a theoretical multivariable simulation of the cutting edge wearing process, employing all experimental variables, was applied, providing a very good explanation of the analyzed problem. 相似文献
6.
利用浙江龙泉和庆元两地在较好立地上营造的21 36年生红豆树、江南油杉、伯乐树、闽楠、刨花楠和乐东拟单性木兰6种珍贵用材树种的片林,以研究其生长、干形和木材基本密度的变化规律。研究结果表明,红豆树是一个树高和胸径生长量大、径生长速生持续期长、木材基本密度中等及其径向均匀性较高的珍贵用材树种,平均年轮宽度达到0.8 1.2 cm,36年生时按宽度和面积计算心材比例分别为60.57%和37.47%。因红豆树分叉干特性明显,在栽植的第2年就应及时修枝抹芽和施肥,以培育树干通直、心材比例高的优质干材。江南油杉和闽楠等其它5种珍贵用材树种皆较少分叉干,其树干通直。闽楠以材质优良而闻名,木材密度中等,虽然其生长速度较慢,但生长势很强,年生长量稳定,加之树冠窄小,适宜长周期大径材的培育;伯乐树生长速度中等,木材密度略低,但其径向均匀性较高,宜作为优质的工艺材来培育;树冠窄小的乐东拟单性木兰生长速度中等,但其木材密度大、径向均匀性高,是优良的珍贵用材树种;江南油杉是个早期生长快而后期生长慢,木材密度中等的针叶树种,可通过加强经营管理延长速生期和提高木材密度的径向均匀性;刨花楠虽然生长速度中等,但其木材密度却较低,浸水有粘液,不宜作为珍贵用材树种培育。 相似文献
7.
Sinikka Mynttinen Kalle Karttunen Tapio Ranta 《Scandinavian Journal of Forest Research》2014,29(1):41-50
The consumption of energy wood in Finland has increased dramatically since the early 2000s, and the region of South Savo is a bellwether for its usage across the country. This increase is partly due to the national policy of sustainable energy, region's wealth of forests but is also dependent on non-industrial private forest owners (NIPF) deciding to sell energy wood. In this study, a survey with a structured questionnaire was conducted among the NIPFs in the region of South Savo to enlarge the understanding of their willingness to sell energy wood in the future and adopt new approaches to forestry that involves energy wood thinning as well as their current production of energy wood. Moreover, the factors influencing forest owner's motivations relating to energy wood thinning as well as information needs were analysed with multivariate techniques. The results show that almost half of the forest owners in the South Savo region had not sold energy wood. However, forest owners within the region generally had positive attitudes towards selling small-sized energy wood and forestry methods that involve energy wood thinning. Moreover, forest owners' willingness to sell different types of energy wood varied, depending on their background. The study suggests that the increase in supply of energy wood presumes both intensified extension services for forest owners and markets that are better organised than at the moment. The results may also prove beneficial in informing policy-makers regarding which specific target group(s) to focus on when promoting energy wood sales among NIPFs and which aspects of energy wood harvesting and sales to promote. 相似文献
8.
Soichi Tanaka Keiichiro Shiraga Yuichi Ogawa Yoshihisa Fujii Shogo Okumura 《Journal of Wood Science》2014,60(2):111-116
The use of an effective medium theory is important when accurately measuring wood density using millimeter and terahertz wave techniques. To confirm the applicability of this theory to the evaluation of wood density, the relative permittivity and dielectric loss of oven-dry flat-sawn specimens of 11 different wood species were measured in a frequency range of 0.15–1.2 THz using a transmission measurement system for terahertz time-domain spectroscopy. A mixture model based on the effective medium theory well explained the density dependence of relative permittivity over the entire frequency range, while it did not fully explain that of dielectric loss, especially for higher frequencies. This indicates that wood scatters the terahertz wave with a wavelength close to the transverse sectional dimensions of the pores in wood in the same way as Mie scattering. It was found from the dielectric loss spectrum of wood substance that the frequency around 0.23 THz was preferable for the nondestructive evaluation of wood. 相似文献
9.
Falcataria moluccana or sengon is one of the fast-growing wood species widely grown in Indonesia.However,its wood is low quality with low density,and poor strength,durability,and dimensional stability.This study determined the effects of impregnation with monoethylene glycol(MEG)and nano-SiO2 on the characteristics of sengon wood,including its dimensional stability and density.Impregnation with MEG and nano-SiO2 had a significant effects on dimensional stability in terms of the weight percent gain,anti-swelling efficiency,water uptake,bulking effect,and density.The impregnated wood was examined by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray diffraction.The results show that MEG and nano-SiO2 were distributed homogeneously into cell walls of wood treated with 0.5%MEGSiO2. 相似文献
10.
《Scandinavian Journal of Forest Research》2012,27(3):241-249
The Brinell hardness and equilibrium moisture content (EMC) were measured from thinning-aged silver birch wood. Wood material both from the trees harvested in the first commercial thinning and from trees remaining on site after the thinning was included. The average Brinell hardness was 19.40 MPa. It correlated significantly with the basic density of wood. With respect to the distance from the pith, the Brinell hardness of air-dried wood was higher than that of artificially dried wood. The average EMC of the conditioned (20°C, 65% relative humidity) wood was 12.0%. The EMC of the wood also varied, with the EMC being higher for air-dried wood than for kiln-dried wood. EMC was the highest at a distance of 30–40 mm from the pith, decreasing towards both pith and log surface. Seasonal variation in both the Brinell hardness and the EMC of the wood was found. It was presumed to be a consequence of season-dependent physiological changes in trees. 相似文献
11.
造林密度对马尾松木材主要性质影响的研究 总被引：1，自引：0，他引：1
本文对贵州省龙里林场马尾松密度试验林 ,5种造林密度 ,15年生马尾松木材基本密度、生长轮宽度、晚材率和解剖特性进行研究。结果表明 :造林密度对马尾松生长轮宽度、晚材率和管胞列数影响较大 ,方差分析达到显著水平。造林密度大 ,则生长轮变窄 ,管胞列数减少 ,晚材率增加。造林密度对马尾松木材基本密度的影响不显著 ,但具明显的规律性 ,即随着造林密度加大木材基本密度增加 ,造林密度过大反而下降。造林密度对管胞形态的影响表现出因树龄而异 ,不同造林密度马尾松管胞形态总平均值变化不大 ,但管胞长度随树龄的增大而增加的趋势受到造林密度影响。较低的造林密度各生长轮管胞长度差异不显著。组织比量不受造林密度影响。 相似文献
12.
13.
选用广西马尾松龄施肥材料（连续观测13年），根据国际《木材物理力学试验方法》，研究了施肥对木材密度和干缩率的影响，结果表明：N、P、K三要素中，以N、P肥对木材密度和干缩率的影响较大。⑴总的来说P增加木材密度和干缩率，N肥降低木材密度木材干缩率。N、P肥降低木材差异干缩。施K肥对木材密度和干缩率的影响规律性不明显。⑵N、P、K施肥对木材密度和干缩率的影响及其变化程度，与肥种、施肥量、树干部位、木纹方向、气干或全干状态有关。施P肥木材密度具有增加的趋势，而且树干下部基本密度方差分析各处理间差异显著。N、K肥对木材密度的影响，规律性不明显。P肥使木材干缩率增加，P肥主要增加的是全干干缩率和径向气干干缩率，特别是树干下部径向气干干缩率各处理间差异显著。K肥对干缩率的影响规律性不明显，有待进一步研究。⑶为了保证木材质量，对于纤维用材林，主要施P肥；对于结构用材林，可施P肥，适当考虑N肥、K肥施用应慎重。 相似文献
14.
对木质材料切削中比较特殊的一类切削方式———无屑切削的切削机理及切削力进行了理论上的研究,并在单板切条试验机上进行试验验证。研究证明,楔型刀锯进行木质材料无屑切削时,其切削力受木材的树种、切削方向、锯片尺寸、角度参数及切削用量的影响较大。 相似文献
15.
Effects of radial growth rate on selected indices for juvenile and mature wood of the Japanese larch 总被引：1，自引：0，他引：1
To examine the differences between juvenile and mature wood, 12 aged sample trees from two areas of Nagano Prefecture were harvested; and the radial development of tracheid length, the ring density, and the relation of the radial growth rate (observed by ring width) with some selected indices of ring structure were investigated. The results proved that the radial variation of tracheid length with ring number can be described by a logarithmic formula, and both plantations reached the demarcation of juvenile and mature wood at age 18. With the segmented regression method, we also analyzed radial variation of mean density and found that the demarcation of juvenile and mature wood was at age 15 for sample trees from Saku and at age 21 for those from Yabuhara. By using the results of estimates from juvenile and mature wood based on ring density, we found that high growth rates resulted when producing lower-density wood during the juvenile period, but these rates did not occur during the mature period. The basic reason for this phenomenon is the variation in patterns of earlywood and latewood in juvenile and mature wood, respectively. This result advised us that when managing plantations of Japanese larch it is necessary to take different measurements at different growth periods. 相似文献
16.
WANG Xiaohuan HUANG Rongfeng ZHENG Hongkui LI Hua LIU Xiuying . Research Institute of Wood Industry Chinese Academy of Forestry Beijing P. R. China . Inner Mongolia Agricultural University Hohhot P. R. China 《中国林业科技(英文版)》2006,5(4):16-22
INTRODUCTION The main body of ancient architecture is wood construction in China, and the main bearing components of the buildings usually use timber, such as pillar, beam, purlin, crossbeam and rafter. Timber is a kind of biomaterial and will be damaged by fungal attack or insects after long time use, which will cause wood frames destroyed ultimately. Timber decay not only exists in its surface, but also usually begins with the inner of wood. It is therefore imperative to consider using … 相似文献
17.
应用热扩散技术测定帽儿山不同径级水曲柳样木生长季的树干液流,初步分析和对比优势木、中等木和被压木树干液流密度的特征及季节变化趋势。结果表明,水曲柳树干液流密度变化具有明显的昼夜节律性,中等木液流密度变化呈单峰曲线,被压木液流密度变化曲线近似梯形,优势木液流密度变化呈弧形曲线,水曲柳中等木液流密度明显大于被压木和优势木。不同天气条件下液流密度日变化规律大不相同,阴雨天液流密度值较小且变化曲线十分不规则,波动性较大,甚至出现多峰曲线。生长季,优势木和被压木日液流通量最大值均出现在7月初至8月耒,分剐为1032．481／（m^2·d）和l063．78I／（m^2·d）;中等木液流通量最大值出现在6月初至6月末,为2260．911／（m^2·d）;优势木和被压木日液流通量最小值出现在9月份,中等木日液流通量最小值出现在生长季未期。,随季节推移,生长季各月份液流密度均值基本逐渐减小,进入生长季末期（10月）基本处于微弱渡动状态。水曲柳优势木和被压木6月份和9月份液流密度平均值均小于中等木,7月份和8月份液流密度月平均值非常接近;中等木液流密度平均值6月份最大,优势木和被压木的液流密度最大月均值出现在7月份, 相似文献
18.
泡桐木材流体渗透性与扩散性的研究 总被引：11，自引：1，他引：11
本文论述了泡桐木材流体渗透性,扩散性,吸着水与自由水的吸着与吸收动力学特性,密度和干缩性以及电镜观察结果;阐明了泡桐木材具有流体可渗透及可扩散路径,有着输导流体的天然机制,水、热处理难易一般;泡桐材本身并不具有隔潮耐湿性,但由于它密度低,胀缩小,变形和开裂的可能性亦小,用它干燥后制成的箱盒容器的密封性、隔潮耐湿性较好。 相似文献
19.
The influences of cambial age and ring width on density of Sitkaspruce (Picea sitchensis (Bong.) Carr) were analysed in relationto within-tree trends in tracheid diameter and cell wall thickness.Discs were sampled at breast height from a total of 24 trees,from seven stands at three contrasting sites in Wales, and atbreast height, 30 per cent and 60 per cent total tree heightfrom one of the stands. Across the juvenile wood, ring density decreased with ring numberfrom the pith while radial tracheid diameter increased. Theseoverall trends were considered to be inherent to tree growth,presumably associated with cambial ageing, since they occurredin all trees on all sites. In juvenile wood, density also variedwith site growth rate (as indicated by ring width) at similarcambial age, wider rings being associated with more rapidrateof change in tracheid diameter with ring number and with decreasein tracheid wall thickness. Consequently, on a site having treeswith high growth rate density decreased more rapidly acrossthe juvenile wood, down to a lower minimum value, than on siteswith a slower growth rate. In mature wood, the decrease in densitywith increase in ring width was associated with differencesin both tracheid diameter and wall thickness. Density was slightly(though not significantly) higher at breast height than in comparablerings at 30 per cent total height, associated with significantlythicker tracheid walls at breast height. Changes in radial tracheid diameter (with ring number, or withring width) were associated with greater differences in theearlywood than towards the latewood end of each growth ring,while variations in wall thickness with ring width were associatedwith rate of increase in wall thickness towards the latewoodend. This may account for some previously conflicting reportson influence of silvicultural management on density, for densityis likely to vary with influence of environment on the seasonalcycle of cambial activity. The extent of the juvenile wood as delimited by the inner coreof wide growth rings does not necessarily correspond to theregion of varying tracheid dimensions in Sitka spruce. 相似文献
20.
Wood density is an important variable in estimates of biomass and carbon flux in tropical regions. However, the Amazon region lacks large-scale wood-density datasets that employ a sampling methodology adequate for use in estimates of biomass and carbon emissions. Normalization of the available datasets is needed to avoid bias in estimates that combine previous studies of wood density that used wood sampling at diverse positions in the bole or with various methods of density determination. This paper examines the question of whether regressions for radial variation and for variation in wood density along the bole, both developed in dense forest in central Amazonia (CA), are suitable for the open forests in southern Amazonia (SA) that are currently the target of most of Amazonia's deforestation activity. The wood density of the heartwood and density of full disks or slices (bark, sapwood and heartwood) in each tree were measured to assess the radial variation. For variation along the length of the bole, wood densities at breast height and at the top of the bole were used. Moisture content of the bole was measured in SA and compared with values reported by studies from CA in similar dense forest. Comparing regressions that predict full-disk density from heartwood density, the pattern of radial variation differs slightly and significantly between the two forest types (ANCOVA p = 0.006); the slopes have similar values but the intercepts differ. Variation along the bole in the two forest types does not differ significantly (p = 0.144), so the CA model for predicting mean bole density from the density of a slice at breast height gives an unbiased estimate of the mean bole density when applied to SA trees. In SA the mean moisture content of the bole was 0.416 (±0.068 S.D.; n = 223 trees). Moisture content of the bole had a strong inverse relationship with basic wood density (r = −0.77), which explains the lower moisture content in the trees in CA relative to SA. A much weaker inverse relationship was found between moisture content and green wood density (r = −0.292). The relationship between wood basic density and green (‘fresh’) density presented in this study provides an alternative means of obtaining basic wood density directly in the field when oven drying of samples is not possible. 相似文献