Effect of growing site,sampling date,wood location in trunk and drying method on concentration of soluble proanthocyanidins in Betula pendula wood,with special reference to wood colour

Proanthocyanidins (PAs), which are common phenolic compounds in plants, are considered to be mainly defensive compounds against different kinds of stress, e.g. herbivory. In addition to increasing after stress, they may condense and/or oxidize to form coloured compounds when cells die, which may affect both the resistance of xylem to rot and its colour. This is important in the mechanical wood industry. The effects of some biological factors (growing site, sampling date, wood location in the trunk) on the concentration of soluble PAs (sPAs) were studied in fresh and dried birch wood. Those factors that affected sPA concentration most were sampling date and radial location. Drying method also had a great effect on the sPA concentration, which in turn correlated with the colour of the wood.     

Shape stability of modified engineering wood product subjected to moisture variation

Abstract

A modified softwood product would enable the utilization of softwood in new areas. Densification is an old modification method to improve wood properties such as hardness and resistance to abrasion. A major problem with densified wood is, however, its ability to retain its original dimensions under the influence of moisture. Therefore, this study investigated the influence of surface to bottom layer thickness ratio on the shape stability of a modified and three-layered cross-laminated engineering wood product (EWP) subjected to moisture variations. The study describes a simple solid wood densification technique based on compressing a clear solid piece of softwood with vertical annual rings in the radial direction by restraining the tangential expansion. Three-layered cross-laminated EWP was manufactured with the densified wood as a surface layer. The recovery of the densified wood in the surface layer was then reduced to movements in the same level as the other two layers of unmodified wood. The EWP was subjected to climatic variations in order to investigate its shape stability. The results disclosed that an appreciable degree of shape stability was obtained by an increase in the surface to bottom layer thickness ratio of the EWP.     

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.     

木醋液对猴樟幼苗土壤养分有效性的影响

以1年生盆栽猴樟幼苗为材料,分别用体积比0%、1%、2%、5%的木醋液进行处理,每7天检测其土壤pH值、电导率值、有机质含量、有效钾含量、有效铁含量,NH₄⁺-N含量、NO₃⁻-N含量和有效磷含量,分析木醋液对猴樟幼苗盆栽土壤养分有效性的影响。结果表明：木醋液处理能影响猴樟幼苗土壤养分有效性,第21天时,各土壤养分含量处于迅速下降或稳定趋势,1%浓度处理的土壤pH值、EC值、NH₄⁺-N含量、有效钾含量、NO₃⁻-N含量和有效磷含量显著低于对照,土壤有机质含量和有效铁含量显著高于对照;2%浓度处理的土壤有机质含量、NH₄⁺-N含量、有效铁含量显著高于对照,而EC值显著低于对照,土壤pH值、NO₃⁻-N含量、有效钾含量和有效磷含量与对照差异不显著;5%浓度处理的土壤有机质含量、NH₄⁺-N含量和有效磷含量显著高于对照,而NO₃⁻-N含量、有效铁含量、有效钾含量显著低于对照,土壤pH值、EC值与对照差异不显著。因此,2%浓度处理对改良猴樟幼苗土壤养分状况效果最好,宜每21天施用1次。     

施用木醋液甜瓜根系生长及根际土壤生物学性状与细菌多样性变化

以盆栽甜瓜为研究对象,基于传统与现代分析技术,探究木醋液对于甜瓜根系生长、根际土壤生物学性状和细菌群落结构的影响,旨在开发木醋液作为液态肥料及土壤改良剂的可行性。结果表明,稀释600倍木醋液处理不仅显著促进甜瓜根系生长、显著提高甜瓜根际土壤中可培养微生物数量以及微生物生物量碳、氮、磷和涉及土壤碳、氮、磷循环相关酶的活性,而且有效地提高了甜瓜根际土壤细菌丰富度Chao 1指数和多样性Shannon指数;另一方面,门或属分类水平上,无论施用何种浓度的木醋液,其优势菌门与对照之间无显著差异,均为变形菌门（Proteobacteria）、放线菌门（Actinobacteria）、酸杆菌门（Acidobacteria）、疣微菌门（Verrucomicrobia）、绿弯菌门（Chloroflexi）;优势菌属均为Subgroup 6_no rank、Saccharibacteria、Gemmatimonadaceae（芽单胞菌属）、Sphingomonas（鞘脂单胞菌属）、Soil Crenarchaeotic Group、Bacillus（芽孢杆菌属）、Rhodospirillaceae（红螺菌属）、Roseiflexus（玫瑰弯菌属）、Lactococcus（乳球菌属）和Acidimicrobiales。施用木醋液没有改变甜瓜根际土壤中细菌优势菌门或菌属的组成,但稀释300倍或600倍木醋液更有利于甜瓜根际土壤形成细菌群落结构更为多样的微环境。综合甜瓜根系生长及指示根际土壤肥力指标的生物学性状,施用稀释600倍木醋液更有助于促进甜瓜生长、提高甜瓜根际微环境的土壤肥力和抵御土传病害的能力。     

处理温度对高温热改性橡胶木物理力学性能的影响

以过热蒸汽为介质常压高温热改性人工林橡胶树木材,处理温度为170、185、200和215℃,处理时间均为3 h。分析了处理温度对热改性橡胶木物理力学性能的影响,结果表明:提高热处理温度,橡胶木的平衡含水率显著降低,降幅为34.33%～62.97%;干缩率显著降低,降幅为3.1%～51.75%(弦向)和2.72%～48.57%(径向);湿胀率显著降低,降幅为37.80%～69.85%(弦向)和28.04%～68.57%(径向);吸水率轻微下降,但不显著;热改性后,橡胶木的尺寸稳定性明显提高。气干密度、全干密度仅在215℃处理时明显下降,其余处理温度变化不显著;弦面硬度先略微增加,后急剧降低,整体呈下降态势;弦、径向局部横纹抗压强度先升高后下降,整体呈增加态势;抗弯强度显著降低,降幅为9.26%～37.52%;抗弯弹性模量有增加,但不显著。     

水杉纸浆材材性变异与利用

报道了水杉木材管胞长义、长宽比、基本密度和化学组分纤维素、木素、多缩戊糖及苯醇抽出物含量的变异模式。结合材积生长最给出了水杉不同树龄木胞形态特征、基本密度和化学组分含量的具体数值。确定了水杉木材幼龄期范围，讨论了水杉作为造纸材主伐林龄的 利用上存在的问题。１２ａ树龄以上的水杉，其管胞长度范围为３．９９９－４．４２２ｍｍ、管胞长宽比８５．７－８９．１、壁腔比０．３６３－０．３５４、腔径比０．７３１－     

一种优化的橡胶树木质部石蜡切片制作方法

针对常规石蜡切片方法无法制得橡胶树木质部切片的问题,优化了橡胶树木质部切片制作方法并进行了验证评估。以3龄和30龄的橡胶树木材为材料,经FAA固定、乙醇预处理后,增加了以冰醋酸软化木质部这一步骤,用正丁醇取代二甲苯进行组织透明,其余步骤参考常规方法。结果表明,优化的石蜡切片方法可制作出完整、高质量的木质部切片,其木纤维的长度、宽度与硝酸离析所得到的木纤维一致度高,为橡胶树成龄木材的解剖学研究提供了方法。     

人工杉木林木材纤维形态变异规律的研究

应用正交试验设计设计,系统分析了不同林龄、不同立地条件和不同林分密度下人工杉木林木材纤维形态的变异规律。结果表明：影响人工杉木林木材纤维形态的主导因子是林龄,其次是立地条件,林分密度影响最小。综合考虑人工杉木林的林龄、立地条件和林分密度对木材纤维形态的影响,其作纸浆材的主伐年龄以１７ａ￣３２ａ左右较好。     

磷氮系膨胀型阻燃剂阻燃性能的热重分析

膨胀型阻燃体系因其高效低毒的特性而受到广泛的关注.研究了以二氨基双酚A、三氯氧磷和三聚氰胺为原料合成磷酰胺类磷氮系膨胀型阻燃剂的反应条件,并用热重分析和灼烧实验方法初步研究了它对杨木粉的阻燃特性.结果表明:用乙醚作分散介质,二氨基双酚A、三氯氧磷、三聚氰胺的摩尔比为1:3:8,回流时间5 h的条件下,磷氮系膨胀型阻燃剂的得率较高、产品质量好;热重分析表明,杨木粉经磷氮系膨胀型阻燃剂处理后,炭化阶段的峰温有所下降,活化能减小,速率常数变大,残余炭量由22.5%增加到36.3%,增加比例达到61.3%;灼烧实验表明,低于230 ℃时,经磷氮系膨胀型阻燃剂处理的杨木粉的灼烧失重大于对照样品,而在高于230 ℃以后,阻燃处理杨木粉的灼烧残余质量大于对照样品;经阻燃处理后350 ℃残余量由24.9%增加到38.4%,比对照样增加54.2%;600 ℃残余量由7.3%增加到22.3%,比对照样增加205%;灼烧残渣为黑色泡沫炭层,具有金属光泽.因此,该阻燃剂在受热时能有效地促使木材形成更多的木炭,并形成石墨样光泽的泡沫炭层.