Anatomical characteristics of thermally modified Eucalyptus nitens wood in an open and closed reactor system

ABSTRACT

Eucalyptus nitens specimens were thermally modified under open and closed systems. The anatomical characteristics from selected modifications that presented similar mass losses were investigated by analyzing images taken from scanning electron microscopy, transmission light microscopy, and X-ray micro-computed tomography. Wood cell wall thickness, fiber, and lumen area were measured and compared to unmodified specimens, and the crack formation after modification was also analyzed. There was only a slight decrease in the measured characteristics when compared to unmodified specimens. The wood cell wall thickness was less affected than the fiber and lumen areas, and both modifications presented similar crack formations. Overall, there were no significant differences between open and closed system modifications in the anatomical structure.     

The effect of compression and incision on wood veneer and plywood physical and mechanical properties

ABSTRACT

Drying takes the largest share of energy in plywood production, and varying moisture content of veneers necessitates re-drying that often leads to over-dry veneers with deactivated surfaces, which may promote imperfect bonding. In order to decrease the drying time, reduce the need for re-drying of veneers, and improve the quality of plywood, birch and spruce veneers were subjected to pre-treatment by cold compression, incision, or a combination of the two. The effects of pre-treatment on the veneer and plywood quality were assessed by standard tests. Compression had a beneficial effect on water removal of the wettest veneers (spruce sapwood (SW) and birch), but some thickness reduction was observed in the veneers as well as the finished birch plywood. Compression led to thickness reduction of spruce veneers, but had no effect on SW plywood thickness likely due to higher viscoelasticity. Both compression and the combination of incising and compression levelled the moisture variation within the compressed stacks. Incision improved the modulus of elasticity of birch plywood, shear strength of SW plywood, and both bending and shear strengths of heartwood plywood. Higher surface pressure decreased the drying time of spruce SW in both plain compression and combined incision and compression pre-treatment.     

Genetic characterisation of a Eucalyptus nitens base breeding population in South Africa

The measurement and statistical analysis of data from eight Eucalyptus nitens trials, established in the summer rainfall forestry region of South Africa during the 1980s and 1990s, have enabled the characterisation of the Institute for Commercial Forestry Research's breeding population. Provenance testing showed that the more northerly New South Wales (Australia) Eucalyptus nitens provenances of Barren Mountain and Barrington Tops are distinctly better suited to the summer rainfall areas of South Africa than the southern New South Wales provenances and the Victorian provenance, Penny Saddle. Generally, the species was not badly affected by Coniothyrium canker. High type B genetic correlations for all site pairs, except one comparison, ranged from 0.75 to 0.99 for diameter at breast height (dbh), indicating very little or no genotype × environment interaction for dbh for the genotypes tested in this study. Narrow-sense heritability coefficients ranged from 0.01 to 0.34, indicating that the species generally exhibited sufficient breeding opportunity for improvement of diameter growth. High genetic correlations of greater than 0.90 between diameter measurements at 52 to 62 months after establishment and diameter measurements at 94 or 113 months were found, indicating that selections can be reliably made at five or six years. Predicted genetic gains were highest in the trials at Goedehoop and Arthur's Seat, with increases in dbh of 3.07 cm (17.1%) and 3.17 cm (20.7%), respectively, at full rotation.     

Endothia gyrosa associated with severe stem cankers on plantation grown Eucalyptus nitens in Tasmania,Australia

Severe stem cankers in Eucalyptus nitens, from a 14-year-old mixed provenance plantation, were associated with infection by Endothia gyrosa, present in its teleomorph state. Surveys of incidence among canker severity classes were carried out in a thinned and pruned stand and an adjacent unthinned and unpruned stand within the affected plantation. No differences in incidence among the canker severity classes were found between the thinned/pruned and unthinned/unpruned stands or between different crown dominance classes within the unthinned/unpruned stand. However, the incidence among canker severity classes was strongly associated with bark roughness with 97% of rough-barked trees developing either annual cankers or cankers causing cambial damage. Stem cankers were found on only 11% of trees with smooth bark. Bark roughness in E. nitens was shown to differ significantly between provenances. Deployment of provenances prone to rough bark in routine plantation establishment may pose a risk of damaging stem canker outbreaks.     

桉树胶合板材林栽培与无性系早期选择

对GR518等10个桉树无性系胶合板材测定林1.5年生生长及栽培模式进行选择和评估研究,结果表明：早期生长中修枝对生长影响较小,各修枝水平间生长差异不显著,而随着林分密度的增加,无性系生长性状有增加的趋势;不同无性系树高、胸径、单株材积及单位面积蓄积生长水平均存在极显著差异,而生长性状除树高外,另外3个指标在无性系与区组的交互效应上也存在显著差异;经单位面积蓄积的多重比较,KC29、GR518和DH32-28在10个无性系中生长最优、保存率高,是今后胶合板材优化培育模式研究中值得重视的无性系;不同性状无性系重复力较高,说明选择在该地进行示范的所有参试无性系能较好地保持亲本优势且稳定遗传,符合进行示范的选择要求,在30%入选率下,性状遗传增益在11.29%~51.80%之间。     

人工林杨木旋切单板背面裂隙率的研究

利用人工林杨木生产人造板,可以缓解我国天然林木材资源短缺的问题。实验表明：杨木生材旋切出的单板表面光洁,背面裂隙率较低,能够满足生产要求。     

中国桉树人工森发展现状和实木加工利用前景

概述了桉树人工林发展与加工利用的现状。全面分析了桉树人工林作为实木用材存在的问题与发展的潜力,指出桉树人工林实木利用具有很好的发展前景。建议将桉树人工林培育与木材性质及加工利用结合起来进行研究,实现按树人工林作为实木用材树种的定向培育、合理、高效利用。     

广东桉树林土壤物理性质及其影响因子分析

研究了广东省桉树人工林土壤体积质量、孔隙度、水分含量现状、各指标之间的相关关系以及海拔、坡度和土壤有机质对上述物理性质的影响。结果表明:广东省桉树人工林土壤A层总孔隙度、毛管持水量、全容水量、吸湿水含量显著高于B层,A层体积质量显著小于B层;不同区域土壤A层体积质量、总孔隙度、非毛管孔隙度和全容水量存在显著差异;除了非毛管孔隙度仅与全容水量(A层)、毛管持水量和毛管孔隙度(B层)显著相关外,土壤其他物理性质之间均呈显著或极显著相关性;土壤体积质量与毛管孔隙度、毛管持水量、全容水量的最佳回归方程分别为对数方程、一元二次方程和指数方程;海拔和坡度显著影响表层土壤的物理性质,对B层影响不显著;有机质对土壤A、B层物理性质均有显著影响。     

邓恩桉木材性质研究进展

邓恩桉（Eucalyptus dunnii）具有耐寒、生长速度快、材性好的特点,已引起越来越高的重视。从邓恩桉木材纤维、物理性质、化学性质等方面介绍了国内外的研究现状。认为木材力学性质和加工利用方面的研究有待全面深入,应与良种选育结合,采用先进仪器设备和分子辅助标记技术提高研究效率。     

桉树第二代萌芽林黄化原因调查及防治对策

通过林地调查和室内分析化验,结果表明广西楼梯坳林场桉树二代萌芽林黄化的主要原因是:林地土壤条件差,土层薄且砾石多;代换性Fe、Mn含量低,有效性差;林地未抚育,通风透气透光差。针对上述原因提出了相应的防治措施:合理施肥即以有机肥为主,添加Fe、Mn等微量元素;及时抚育增加土壤裸露和林内通风透气透光,可以防治桉树二代萌芽林黄化。     

广西桂中桉树人工林风险防控

近10年来广西桂中桉树发展迅速,所占比例为广西的桉树1/3,成为木材加工的主要原料,但仍存在不少经营风险,主要是品种单一、病虫害隐患大、抚育施肥粗放、霜冻灾害影响、生态环境安全等。本文针对所隐藏风险,提出防控规避建议,包括加强品种选育,增加造林品种;采取营林措施,病虫害采用综合防治;合理配方施肥,加强施肥除草管理;根据立地条件,做好区域树种规划;合理生产经营措施,保护生态环境等建议。     

蓝桉幼林施肥效应研究

在云南省保山市石灰岩红壤地区进行了历时4年的蓝桉幼林N、P、K不同配比的10种处理施肥试验。结果表明，施肥能明显促进蓝桉（Eucalyptusglobulus）幼林的生长；其中处理6、9、10增产效果极显著，树高增加16．31％～20．40％，胸径分别增加18．78％～19．21％，材积增加65．04％～70．19％。有机肥对蓝桉生长有促进作用，施过有机肥的处理10生长始终保持优势；磷肥是蓝桉增产的主要因素，每株施430g钙镁磷肥做底肥能使树高、胸径分别增加14．67％、15．87％，每株施215g钙镁磷肥则树高、胸径分别增加11．44％、7．83％；氮肥各水平间无差异，增产效果不明显；钾肥1、2水平间无差异，3水平可能过量，阻碍了肥效发挥。施肥能提高蓝桉生产的经济效益，较好的几个处理依次为6、9、2、10、3产出投入比值均大于对照。综合以上几个因素，N2P3K2为蓝桉幼林的最佳施肥方案。     

热带北缘地区种植桉树前后林下植被的变化

分析我国热带北缘地区炼山营造的桉树(Eucalyptus)人工林前后林下植被物种组成与生长的差异,初步探讨桉树与林下植被的关系,为我国热带地区的桉树种植提供参考。造林前的植被包括3个马尾松(Pinus massoniana)林和1个果树林,炼山后全部种植桉树。结果表明:炼山造林2 a后,林下植被得到恢复,其种类组成没有发生改变,而频度的变化则与植物类型有关,频度减小的以灌木为主,频度增大的以草本为主。果树林改造为桉树林后,林下植被出现了一些新的物种,且物种平均高度大幅增加;马尾松林改造为桉树林后,多数物种的平均高度和盖度接近原有群落的水平,而芒萁(Dicranopteris dichotoma)从林下植被层消失,割鸡芒(Hypolytrum latifolium)盖度大幅提高,表明种植桉树对林下植被的影响因物种而异。经过炼山造林,在广东省茂名地区种植桉树对少数物种影响较大,短期内没有降低林下植被的多样性,长期是否存在影响还需要进一步观察。     

桉木单板层积材家具角部“L型构件”接合强度研究

以速生桉木单板层积材为基材,榫接合连接、螺钉连接的L型构件为研究对象,通过对桉木层积材家具接合构件进行抗拉和抗弯力学性能试验,观察、分析8种不同榫接合方式对"L型构件"接合强度的影响。研究结果表明,榫接合强度与接合面积有关,接合面积大则接合强度高;桉木单板层积材本身强度对榫接合无影响;采用偏心连接件、倒刺螺母螺杆连接件的接合强度较低,接合部位不够牢固,在家具的使用过程中容易产生松动。     

The Brazil Eucalyptus Potential Productivity Project: Influence of water,nutrients and stand uniformity on wood production

We examined the potential growth of clonal Eucalyptus plantations at eight locations across a 1000+ km gradient in Brazil by manipulating the supplies of nutrients and water, and altering the uniformity of tree sizes within plots. With no fertilization or irrigation, mean annual increments of stem wood were about 28% lower (16.2 Mg ha⁻¹ yr⁻¹, about 33 m³ ha⁻¹ yr⁻¹) than yields achieved with current operational rates of fertilization (22.6 Mg ha⁻¹ yr⁻¹, about 46 m³ ha⁻¹ yr⁻¹). Fertilization beyond current operational rates did not increase growth, whereas irrigation raised growth by about 30% (to 30.6 Mg ha⁻¹ yr⁻¹, about 62 m³ ha⁻¹ yr⁻¹). The potential biological productivity (current annual increment) of the plantations was about one-third greater than these values, if based only on the period after achieving full canopies. The biological potential productivity was even greater if based only on the full-canopy period during the wet season, indicating that the maximum biological productivity across the sites (with irrigation, during the wet season) would be about 42 Mg ha⁻¹ yr⁻¹ (83 m³ ha⁻¹ yr⁻¹). Stands with uniform structure (trees in plots planted in a single day) showed 13% greater growth than stands with higher heterogeneity of tree sizes (owing to a staggered planting time of up to 80 days). Higher water supply increased growth and also delayed by about 1 year the point where current annual increment and mean annual increment intersected, indicating opportunities for lengthening rotations for more productive treatments as well as the influence of year-to-year climate variations on optimal rotations periods. The growth response to treatments after canopy closure (mid-rotation) related well with full-rotation responses, offering an early opportunity for estimating whole-rotation yields. These results underscore the importance of resource supply, the efficiency of resource use, and stand uniformity in setting the bounds for productivity, and provide a baseline for evaluating the productivity achieved in operational plantations. The BEPP Project showed that water supply is the key resource determining levels of plantation productivity in Brazil. Future collaboration between scientists working on silviculture and genetics should lead to new insights on the mechanisms connecting water and growth, leading to improved matching of sites, clones, and silviculture.     

我国桉树人工林资源和木材利用现状

本文概述了我国桉树人工林资源状况,分析了桉树人工林木材性质的研究及加工利用现状，指出桉树人工林木材利用的巨大潜力，并对我国桉树人工林的可持续发展提出建议。     

澳大利亚塔斯马尼亚林业公司人工桉树林经营模式及启示

考察了澳大利亚塔斯马尼亚林业公司的桉树经营管理模式。土地平整、人口稀少、土壤肥力较低,是该林业公司机械化作业、集约化经营、主伐年龄较大的缘由。他们采取的经营模式对于我国速生丰产林建设有一定的启示意义。     

重视桉树人工林生态环境管理，提高科学经营水平

本文在我国桉树人工林稳定发展的新的历史时期,提出从5个方面加强桉树人工林的生态环境管理：加强植被管理,增加林地生物多样性;采取合理的营林措施,既增加桉树生长量,又保护周边环境;做好桉树肥料的施放管理和重金属的检测;及时做好病虫害的预测预报,用生物和物理等防治办法控制病虫害发生;加强伐区管理和林区建设,及时进行迹地更新。从而充分发挥桉树人工林的正面效应,维护人工林的自然生态环境,提高科学经营水平,促进可持续发展。     

海南桉树人工林直径分布模型

桉树是我国南方种植面积最大的人工林树种,研究其直径分布有助于实现可持续经营。采用Normal分布函数、Logistic分布函数、Weibull分布函数和Γ分布函数拟合和检验了海南省文昌、琼中、昌江以及乐东桉树人工林直径分布。结果表明:4个模型中,Normal分布函数和Weibull分布函数对文昌桉树人工林直径分布拟合效果较好,Weibull分布函数对琼中、昌江和乐东桉树人工林的模拟结果较可靠。     

广东省桉树人工林发展现状与可持续发展对策

文章介绍了广东省桉树人工林发展现状,阐述了发展的优势及潜力,分析了发展中存在的问题,并提出了今后桉树人工林可持续发展对策。