桉树真空热处理材表面性能分析

用真空热处理法对粗皮桉木材进行热处理,处理温度分别为160,180,200,220及240℃,处理时间均为4 h.采用接触角测定法,对素材及不同温度条件下热处理材的接触角及表面自由能进行分析;用傅里叶红外光谱分析法,研究木材在热处理过程中的化学(官能团)变化;用热分析仪分析不同温度条件下木材的热解质量损失率.结果表明:素材的表面自由能(50 mN·m-1)<160℃热处理材的表面自由能(46 mN·m-1)<240℃热处理材的表面自由能(32 mN·m-1).热处理后木材中极性的羰基官能团减少,当热处理温度≤180℃时,木材的质量损失率在1%左右;而热处理温度>180 ℃时,每升高20℃,木材的质量损失率约下降2倍.     

脱木质素处理对木材组分和物化性能的影响研究北大核心

脱木质素是提高木材性能、制备新型木基功能材料的重要方法之一。采用由亚氯酸钠、冰醋酸和蒸馏水混合而成的改性剂对木材进行脱木素处理,研究脱木质素对木材材性的影响,并以残留木质素含量为指标,经单因素和正交试验获取最优工艺。结果表明:当亚氯酸钠溶液浓度为4 wt%、处理温度为100℃、处理时间为6 h、处理液浴比为1∶30时,残留木质素的含量均值为0.081 g。经过脱木质素处理后的木材,其材色变亮,质量损失率增加,吸水率明显提高。其中,明度值L*从52增加到85,质量损失率增至26%,吸水率从1.39%增至3.44%。研究结论可为脱木质素木材材性的综合评价及其加工利用提供理论依据。     

高温热改性橡胶木的生物耐久性

以水蒸气作为保护气体,在170,185,200和215℃的条件下分别热处理橡胶木3h,对热改性橡胶木的生物耐久性进行研究.结果显示:高温热改性可提高橡胶木的耐腐性,其改善效果随着处理温度的升高而提高,当处理温度为185℃或更低温度时,改善效果不明显.215℃处理3h后,褐腐(密黏褶菌)质量损失率由51.6％降至21.6％,白腐(采绒革盖菌)质量损失率由27.6％降至6.8％.选用烟曲霉、哈茨木霉、产紫青霉和可可球二孢进行防霉试验,结果显示热改性橡胶木的防霉性能与对照相比没有明显的改善;经涂饰后,热改性试材的防霉性能优于未处理材.野外耐久性试验结果显示,高温热改性不能提高橡胶木的防白蚁性能.     

杉木热处理材的耐腐性研究

采用白腐茵(彩绒革盖茵)和褐腐茵(绵腐卧孔菌),对不同温度热处理前后杉木木材的耐腐性进行研究.研究结果表明:热处理材的处理温度对白腐茵腐朽性没有影响,而褐腐茵对热处理材的腐蚀性随温度的上升而下降,当温度升至220℃时,木材的质量损失率降为0,耐腐性上升为Ⅰ级强耐腐等级.     

热处理橡胶木的有机酸释放量及其对材性的影响

为了改进橡胶木热处理工艺,采用过热蒸汽作为传热介质,进行橡胶木热处理,检测处理过程中,橡胶木释放有机酸的量,并探讨有机酸对材性的影响.结果表明,提高热处理温度,延长高温阶段处理时间,试材释放有机酸量增加;随着有机酸释放量的上升,橡胶木的平衡含水率降低,质量损失率增加,颜色变深,抗弯强度下降,耐腐性改善.     

铜唑与石蜡防水剂复配处理南方松的耐褐腐性能

为了明确石蜡对铜唑(CA)浸漬木材及处理材耐褐腐性能的影响,配制了不同质量分数的CA处理液和石蜡处理液,以及不同质量分数比例的CA/石蜡复配处理液,然后分别处理南方松试材,并考察浸渍效果和抗流失性,同时基于褐腐质量损失率以及扫描电镜、傅里叶变换红外光谱和X射线衍射方法,对试材的耐褐腐性能进行分析.结果表明:石蜡不会对C...     

软枣猕猴桃花青素加工稳定性研究

花青素的稳定性易受加工条件的影响,为提高花青素在果蔬深加工过程中的稳定性,以软枣猕猴桃为试材,对其花青素进行提取,比较光照、pH值、温度及金属离子对花青素保存率的影响。结果表明:避光处理是软枣猕猴桃花青素加工过程保持稳定性的有效方法;pH值3.0、温度25℃时花青素稳定性始终保持在较高水平;K^+、Na^+、Ca^2+对保持花青素的稳定性显著优于Mg^2+、Cu^2+。     

模拟酸雨对盆栽广玉兰幼苗叶矿质元素含量的影响

以广玉兰为试材,采用盆栽方法,配制3种不同pH值(3.0、4.0、5.0)的模拟酸雨溶液对幼苗进行浇灌处理,分析了不同pH值的酸雨对幼苗叶中矿质元素含量的影响.结果表明:盆栽广玉兰幼苗经模拟酸雨浇灌处理后,幼苗叶中矿质元素含量受到一定程度的影响;3种酸雨处理的幼叶中P、Mg、S含量均较对照有所增加,Ca、Zn、Mn、Ni、Cd含量均下降,N、Fe、Cu、Pb变化趋势相同,即都是pH3.0处理含量增加,pH4.0和pH5.0处理下降;C、K、Al含量不随酸雨pH值改变而变化,其中C含量pH3.0、pH4.0处理增加,pH5.0处理下降;K含量pH3.0和pH5.0处理下降,pH4.0处理增加;Al含量pH3.0、pH5.0处理增加,pH4.0处理略微减少.该项研究可为南方城市绿化树种的选择提供理论依据.     

碱性亚硫酸盐法脱木素工艺参数对巴沙木性能影响的研究

脱木素处理是开发功能性木质复合材料常用的工艺方法,木质素的去除改变了处理材的物理力学性能,进而对制备的复合材料产生影响。研究考查了碱性亚硫酸盐法脱除巴沙木木质素过程中,溶液浓度和处理时间对巴沙木质量损失、接触角、色差以及比表面积的影响。通过建立工艺参数与处理材物理力学性能之间关系,为功能性木质复合材料的预处理工艺提供理论依据。结果表明:相比未处理材,脱木素处理材质量损失率随溶液浓度和处理时间的增加而增加;颜色偏向明亮黄绿色,颜色变化与工艺参数没有显著关系;处理材亲水性显著提高,与工艺参数无关;处理材的宏观比表面积与未处理材相比略有降低。     

硅溶胶/聚乙二醇/硼盐/丙烯酸酯复配药剂改性木材的性能研究

五桠果（Dillenia sp.）木材易霉变开裂,采用聚乙二醇和硼盐复配处理可提高其尺寸稳定性和抗菌性,但药剂遇水易流失。本研究以聚乙二醇为尺寸稳定化药剂,硼盐为抗菌剂,辅以硅溶胶和丙烯酸酯对五桠果木材进行改性处理。以复配药剂聚合物溶胀率和质量损失率为指标,研究复配药剂最佳配比,采用红外光谱和扫描电镜对其反应产物进行表征。在此基础上,将复配药剂浸入木材内部加热固化,分析处理材的微观形貌、尺寸稳定性和防霉性能。结果表明：硅溶胶、聚乙二醇、硼盐和丙烯酸酯质量比分别为30%、20%、2%和8%时,形成的凝胶溶胀率和质量损失率最低。扫描电镜观察复配药剂干燥产物发现,在硼盐和丙烯酸酯作用下,硅溶胶可将聚乙二醇固定其中。复配药剂改性五桠果木材在吸湿-干燥和吸水-干燥循环试验中的抗胀率最高达到46%,处理材泡水后药剂流失率较聚乙二醇处理材降低约42.5%;处理材在一个月的室内综合防霉测试中未出现霉变。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.