不同计算方法杉立木材积差异及其相互关系分析

通过对兰溪市采伐杉立木2m区分段材积（作为立木真实材积）、实验形数材积、根径一元材积、胸径一元材积、原条折算材积、木材重量折算材积的比较分析，得到实验形数材积与2m区分材积之间无显著差异，在实际应用中可作为立木真实材积；其它计算方法材积与2m区分材积之间差异显著，但存在显著回归关系；原条出材率明显大于省定综合出材率，应根据情况加以材积转换。     

木材材积计算方法探讨

指出了树木材积是伐根以上树干的材积,木材材积是原木生产和销售的重要数据,主要通过分析现用木材材积的计算方法,探讨了材积计算方法的科学性和实用性,以提高木材材积计算的精准度,对现实具有指导性意义。     

东北阔叶红松林主要树种心腐相关式

一、调查地区的地理位置及工作方法调查地区选在小兴安岭的新青林业局,完达山的穆棱林业局和长白山的松江河林业局。调查林分均属灌木阔叶红松林。调查树种有红松、云杉、臭松、椴树、枫桦和色木。调查内容有心腐率和心腐材积。心腐率是指心腐株数占调查株数的百分比,而心腐材积是指病腐木心腐部分材积。心腐率通过新采伐迹地的伐根调查取得。心腐材积则通过伐区伐倒木调查及贮木场造材获取。在调查中量测了心腐木的心腐长度、心腐直径及胸径。所谓木材心腐是指木材颜色有了明显改变,其材质发生变化的部分。     

如何简化设计和考核森林采伐量的主要指标

在控制、设计和考核森林采伐时,采用活立木蓄积和木材材积双重指标,有着重复、设计繁琐复杂、工作量大、实施困难和在考核时活立木蓄积标准与木材材积标准不能统一等不足。活立木蓄积是木材材积的母体,蓄积的多少控制着木材材积的多少,而利用木材材积计算森林采伐的收入和支出,可以利用树高、胸径、蓄积和木材价格的关系进行计算,这样只利用活立木蓄积作为控制、设计和考核森林采伐的主要指标,可以简化设计技术环节,降低工作量,设计考核更加准确,更加符合实际。     

采伐方式对速生桉木材变形与开裂的影响

桉树木材易变形、开裂,对其加工和利用影响较大。通过采用3种不同的采伐方式,即环割后伐倒造材,伐倒后留冠放置再造材,按传统的采伐方式采伐后直接造材,探讨了采伐方式对速生桉木材变形与开裂的影响。结果表明:在3种不同的采伐方式中,伐倒留冠处理的开裂及翘曲程度最轻,环割处理的开裂情况最严重。伐倒留冠9 d后造材的裂纹比值比采伐后直接造材的下降了76.48%;伐倒留冠29 d后造材的锯材翘曲度比采伐后直接造材的下降了45.24%。说明伐倒留冠的采伐方式能有效减轻速生桉树木材的开裂和变形。     

木材增产新途径

过去我局生产木材多采用斧头砍伐,由于伐口过大,伐桩偏高,使许多木材变为废渣废料,白白损失掉,降低了木材利用率。1987年宽滩林场结合经营采伐生产,对传统的采伐作业方式作了改进,即采取斧劈树根降低伐桩后,用弯把锯贴地伐木。此法与斧头砍伐相比,不仅降低了伐桩高度,而且伐口亦大大缩小,从而使过去伐口处变为废渣和干基部变为伐桩的木材都变废为宝,增加了干材长度,出材量平均提高达8％。该场去年仅经营采伐100亩即多生产木材121.51立方米,增收29 968元。采伐方式的这一改进,为次生林经营开辟了一条增加木材产量     

应用电子计算机确定立木材种材积

立木材种材积是林业企业工业活动的决定因子,因此,在调查资料的基础上,借助电子计算机精确地确定立木材种材积是森林资源清查工作的主要任务之一。现在,我们在树干模型的基础上考察这个问题。在林业科学和木材采伐实践中已被确认的树干数学模型有:     

这起超伐林木案应如何处理

甲某向林业主管部门提交了申领林木采伐许可证的申请书。采伐方式为皆伐,采伐指标约为150立方米。林业主管部门对申请审查后,同意皆伐,及时安排林调队进行了规划设计,经测算材积为190立方米。     

长白落叶松人工林经营采伐和迹地更新的研究

运用林木工艺成熟和经济成熟的观点,有效地利用长白落叶松人工林材积生长最佳期,生产中小径材,缩短培育周期,缓解木材供需矛盾。对森林后备资源雄厚、中龄林比重大、无主伐任务的国营林场切实可行。经5年试验研究表明,林龄25～30年为采伐的最佳期,经营采伐86.43 ha,平均获利润15 678元/ha。为林业扩大再生产提供了资金,达到了合理调整树种结构和轮伐期及发展多种经营的目的。为落叶松经营采伐、更新提供了科学依据。     

阔叶树重量估测法

一、前言树木有材积与重量两个计测单位。在把树木作为结构用材时,材积是较理想的计测单位。因为重量会随着树木干燥程度的不同而发生很大差异,而材积几乎不存在这种差异,显然,使用材积更简单方便。但从目前将树木作为可再生产能源来考虑的情况下,重量无疑比材积更理想。为此,本文拟就估测一棵刚伐倒的阔叶树湿材重量的最有效方法     

现代电子称重技术发展对森林收获计测的影响

回顾森林收获计测技术的发展历史,分析现代电子称量技术的发展应用前景,指出木材及木制品以体积计量计价的局限性和以重量计量计价的优势,认为当前一些木材市场上出现的买卖双方以重量而不是以材积计量计价现象有其历史必然性。基于以重量计量计价更为客观、准确、快捷、高效,并大幅降低成本的优势,其在纸浆等工业原料林经营、林业碳汇贸易等方面具有广泛应用潜力。     

Biomass conversion factors (density and carbon concentration) by decay classes for dead wood of Pinus sylvestris, Picea abies and Betula spp. in boreal forests of Sweden

For estimating the amount of carbon (C) in dead wood, conversion factors from raw volume per decay class to dry weight were developed using three different classification systems for the species Norway spruce (Picea abies L. Karst), Scots pine (Pinus sylvestris L.) and birch (Betula pendula Roth and B. pubescens Ehrh) in Sweden. Also the C concentration in dead wood (dry weight) was studied. About 2500 discs were collected from logs in managed forests located on 289 temporary National Forest Inventory (NFI) sample plots and in 11 strips located in preserved forests. The conversion factors were based on an extensive data compilation with a wide representation of different site-, stand-, species- and dead wood properties and were assumed to represent the population of fallen dead wood in Sweden. The density decreased significantly by decay class and the range in density for decay classes was widest for the NFI decay classification system, suggesting this to be the most suitable. The C concentration in dead wood biomass increased with increasing decay class and in average Norway spruce (P. abies) showed a lower C concentration than Scots pine (P. sylvestris). The average dead wood C store of Swedish forests was estimated to 0.85 Mg C/ha.     

Potential Measures for Use in Developing Selection Procedures for High Timber Density in Juvenile Wood of Picea sitchensis

Four clones of Picea sitchensis, each growing on two sites with contrasting growth rates, were examined for the rate at which wood density decreased as growth rate increased during successive years of juvenile wood formation. The clones with the greatest and least rates of change were consistent between contrasting sites. It was determined that the most effective measure of change in wood density was the relative rates of increase in wood volume and wood weight increment in successive annual increments. Wood volume increased more rapidly than wood weight for all clones but there were differences between them. The rankings for these relative rates of change were not (he same as those for mean density nor density of the last annual wood increment. Within a single annually produced sheath of wood, wood density was found to decrease with increasing distance down the main stem. In the outermost sheath, volume increment was at a maximum at least two and more usually three interwhorl positions. Dierences between clones in the patterns of weight and volume increment along the main stem are related to differences in crown structure. It is suggested that small height increments along the main stem lead to inadequate surface area for cambial development relative to the available resources for growth.     

Dead wood volume to dead wood carbon: the issue of conversion factors

Requirements for emission reporting under the Kyoto protocol demand an estimate of the dead wood carbon pool in forests. The volume of dead wood consists of coarse woody debris, smaller woody debris and dead roots. The measurement of dead wood volume was included in the most recent National Forest Inventory in Switzerland. To convert dead wood volume into carbon two conversion factors are required: (a) carbon (C) concentration and (b) wood density. So far internationally accepted default values for C concentration (50%) and for wood density (density of alive trees) were used as default values to estimate dead wood carbon, since local measurements were lacking. However, in a field study at 34 sites in Switzerland, the C concentration and density of CWD from Picea abies and Fagus sylvatica of four decay classes were measured recently. The results showed that C concentration in CWD differed significantly between species but did not change due to decay class. The density of CWD decreased significantly with an increase in decay class and it also differed between species. The decrease in CWD density was more pronounced for F. sylvatica than for P. abies. We assessed correlations between climate attributes and CWD density using regression analysis. The modeled densities and measured C concentrations were then expanded with the help of CWD volume data from the NFI3. Spruce CWD and thus spruce CWD carbon is much more abundant in Swiss forests than beech CWD carbon. The majority of spruce CWD is located in the Alps and Pre-Alps. The CWD volume from P. abies was 10 times higher than that from F. sylvatica. Thus, changes in conversion factors for P. abies CWD affected the overall estimate of dead wood carbon in Swiss forests much more than changes in conversion factors for F. sylvatica CWD. Current improvements in CWD conversion factors decreased the estimated amount of spruce CWD carbon by 23.1% and that of beech by 47.6%. The estimated amount of CWD carbon in Swiss forests is decreased by 31%. Since improved estimation methods are currently not applied to smaller woody debris and dead root material, the estimated amount of dead wood carbon is only reduced by 15%. Improving conversion factors for all dead wood fractions would presumably decrease the amount of dead wood carbon by additional 16%.     

Initial Moisture Content and Density and Drying Rate of Three Pine Species Growing in the Natal Midlands

In this the first of a two-part report, results are given of investigations into the vertical distribution of the moisture content and density of wood and bark, as well as into bark thickness, bark mass and bark volume of two age groups of Pinus elliottii and P. patula trees and one of P. taeda. Variation in wood and bark properties was affected more by position in the stem than by species and age. This precludes the determination of reliable mass/volume conversion figures if stem position is not taken into consideration. The mass loss of logs of the above species after various periods of drying and the development of mass/volume conversion figures will form part of a further report.     

世界制材工业现状及发展趋势

本文概述了世界制材工业现状，从林木资源利用、提高锯材质量、完善加工工艺、开展小径木加工，采用高新技术等方面，介绍和论述了世界制材工业的发展趋势。针对我国制材工业的现状和存在的问题提出了解决对策。     

Reversible volumetric changes of acetylated wood with after-treatments

Dimensional changes of acetylated wood were measured during wet–dry cycling and heating to clarify the reversible and irreversible effects of those after-treatments. During wet–dry cycling, the acetylated wood showed slight swelling in its completely dry condition, while its weight decreased slightly. Similar swelling was recognized when the acetylated wood was heated dry above 140°C. On the other hand, the anomalous effects of wet–dry cycling and heating disappeared after soaking in acetone. It was considered that the rearrangement of hydrophobic wood polymers during wet–dry cycling and heating induced the expansion of voids, whereas the wood polymers recovered their initial conformation after soaking in organic liquids. The wet volume of acetylated wood also exhibited reversible changes during wet–dry cycling. Just after the acetylation, the wood was highly swollen in acetic anhydride. The swollen volume of acetylated wood was reduced by leaching in water, and additional decrease in the wet volume resulted from the following drying or boiling. However, the reduced wet volume was recovered almost completely after acetone-soaking. These results suggested that the water molecules remaining in the hydrophobic region expanded the wet volume of acetylated wood, while such weakly bound water was easily removable by drying or boiling.     

Compressive deformation of phenol formaldehyde (PF) resin-impregnated wood related to the molecular weight of resin

The effects of molecular weight of PF resin on the deformation behaviour of NaClO₂ treated resin-impregnated wood during compression were investigated. Blocks of Japanese cedar were subjected to 2% NaClO₂ aqueous solution. This was repeated up to four times resulting in a weight loss of 28%. Treated and untreated samples were impregnated with PF resin having different molecular weight. With increasing molecular weight, weight gain and volume gain decreased for untreated PF resin-impregnated wood, while NaClO₂ treated wood impregnated with high molecular weight PF resin showed almost double the weight gain compared to untreated condition. NaClO₂ treatment has shown considerable potential for high compression of PF resin-impregnated wood at lower pressing pressure regardless of the molecular weight of the resin. Low to high molecular weight resin was shown to penetrate into NaClO₂ treated wood as estimated by weight gain contributing to the plasticization of cell wall considerably and thus resulting in cell wall collapse at low pressing pressure. The density of NaClO₂ treated wood impregnated with high molecular weight resin attained a value of over 0.8 g/cm³ which is close to the density of untreated wood impregnated with low molecular weight resin. Such compressed wood exhibited high dimensional stability after boiling for 3 h. Thus, the penetration of resin into wood contributes to highly compressed dimensional stable resin-impregnated wood at low pressing pressure.     

高压放电法、传导法及二者结合法干燥木材比较实验研究

采用高电压放电法干燥木材能实现木材整体加热,木材整体温度及湿度的均匀分布,在短时间内获得高质量的干燥木材.但高电压干燥法消耗的电能昂贵.热传导法干燥利用木材燃烧废料产生热能,能节约干燥成本.由于这两种方法的压力梯度与温度梯度方向相反,能实现相互抵消补偿,可达到降低沿截面压力梯度的目的,从而获得高质量的干燥木材,因此笔者分别利用高电压放电法、传导法及二者结合法进行了干燥木材比较实验研究.研究表明,利用高电压放电法结合传导加热法干燥木材,能以较少的消耗干燥成本及较短的干燥时间获得高质量的木材.     

广东省马尾松优良亲本的无性系选择研究

对广东省19个马尾松主产区的508个优良马尾松单株，进行了多地点、多重复的选择研究。共选择出马尾松优良亲本和无性系59个。其中，根据子代生长量、花期、种子品质和木材比重四个综合指标评选出23个马尾松最优无性系。入选的最优无性系与CK相比，树高>7.6-20.2％，胸径>15.3-30.9％，材积>42-102％，千粒重>12.26％，发芽率>82.42％，木材比重>12.5％。