刨花形态对竹材自生胶合刨花板性能的影响

利用半纤维素酶/漆酶协同处理3种不同类型的竹刨花,热压制备竹材自生胶合刨花板,研究不同刨花形态对刨花板物理力学性能的影响.结果表明:刨花形态对竹材自生胶合刨花板主要物理力学性能有显著影响,3种刨花形态中,4～16目的细刨花性能最佳,16目以上碎刨花作为填料加到大刨花中有利于提高刨花板弹性模量,减小吸水厚度膨胀率.该结论为进一步研究刨花形态与竹材自生胶合刨花板物理力学性能的关系提供了理论基础.     

漆酶/碳源系统预处理对稻草碎料板性能的影响

利用添加少量碳源与漆酶组成的体系对稻草进行预处理,以改善其压板性能,研究了漆酶预处理的最佳工艺条件、漆酶／碳源系统(LCS)与漆酶／介体系统(LMS)预处理结果比较及酶处理对稻草碎料板性能的影响。结果表明:LCS完全可以代替昂贵的LMS来降解稻草中木质素;预处理最适条件为pH值5.0,温度45℃,液比1:7,时间4-6h,酶用量20-30IU／g;当酶用量为20IU/g,时间4h条件下预处理稻草碎料板的各项力学性能均有显著改善,与粗碎料板相比,酶处理对细碎料板的性能改善效果更是明显:内结合强度(IB)增加20％,静曲强度(MOR)增加21％,弹性模量(MOE)增加31％,吸水厚度膨胀率(TS)降低35％,甲醛释放量可达到F1级标准。     

竹木混合水泥刨花板工艺初步研究

研究了热压法制造竹木混合水泥刨花板工艺并对影响板材性能的因素进行探讨。结果表明:竹刨花水煮预处理后所制备的板材性能较好;本实验范围内,竹木混合水泥刨花板较合适的工艺参数为竹木比1∶3、灰木比4∶1、热压时间1～2min/mm板厚、CaCl2用量为灰重的5%、水灰比0.4。     

漆酶活化木材产生活性氧类自由基的处理条件研究

自由基对漆酶活化木材产生胶合力起着关键性的作用。通过试验分析反应体系pH值、处理温度、酶用量、处理时间及树种等因子，对漆酶处理木粉产生的活性氧类自由基的相对浓度的影响。研究结果表明：5个因子均对活性氧类自由基相对浓度有极显著影响。当采用思茅松心材木粉、处理4h、反应体系pH值为4、酶用量为1．5u／g木粉、处理温度为60℃时，漆酶活化木材产生的活性氧类自由基的相对浓度最高。     

酸预处理对毛竹酶解糖化的影响

竹子富含纤维素和半纤维素,是生产纤维素乙醇的潜在原料来源。而预处理过程是研究的重点和难点之一。本文以毛竹为原料,研究了微波消解稀酸预处理对其化学组成及其酶水解的影响。结果表明,预处理条件为酸用量为2%(w/w干物质),固液比1∶6,温度180℃,时间30min时,能脱除97.2%的半纤维素。预处理得到的底物在酶用量为纤维素酶20FPU/g纤维素和β-葡萄糖苷酶40IU/g纤维素,水解48h,纤维素水解得到葡萄糖的收率由2.41%(未经预处理)提高到52.72%。酶水解过程中,酸不溶木质素的存在,可导致葡萄糖收率的降低。     

纤维素/半纤维素酶处理对杨木表面胶合性能的影响研究

研究了速生杨木单元经过纤维素酶和半纤维素酶处理后的表面润湿性能、化学基团和胶合强度的变化。结果表明:随着纤维素酶和半纤维素酶用量的增加,杨木的表面自由能和胶合强度逐渐上升。在试验区间内,酶处理时间越长,杨木的胶合性能改善效果越明显。     

相思木EMCC硫酸盐浆氧脱木质素前后酶处理的影响研究

研究了酶处理对相思木EMCC(延伸改良连续蒸煮)硫酸盐浆(KP浆)氧脱木质素效果的影响。结果表明,由白腐菌直接合成的漆酶/木聚糖酶体系(LXS)预处理相思木EMCC硫酸盐浆的的适宜酶用量为7 IU/g;LXS预处理后浆料氧脱木质素的适宜反应时间、最高反应温度及用碱量分别为60 min、100℃和2.5%;利用LXS进行氧脱木质素后处理的适宜反应时间及酶用量分别为2 h和5 IU/g。SEM观察到经过酶处理后纤维表面及横切面出现大量的裂隙及孔隙,其中以酶后处理最为明显,为后续漂白中化学药品的渗透和漂白降解产物的溶出创造条件。     

漆酶活化木素磺酸盐条件对胶合板强度的影响

采用漆酶活化木素或其磺酸盐制备胶黏剂用于人造板生产,可以消除游离甲醛的污染问题。以漆酶、工业木素及其磺酸盐、杨木为原料,在处理时间分别为30、45、60min,pH值分别为3．5、4．5、5．5,温度20℃条件下,分别以漆酶处理工业木素、木素磺酸钠和木素磺酸铵三种底物制备胶黏剂,然后在热压时间30min,压力4．5～5MPa,热压温度150℃条件下生产杨木胶合板。结果表明,除漆酶木素磺酸钠胶合体系外,漆酶木素和漆酶木素磺酸铵的胶合体系的胶合板胶合强度均达到并超过国家Ⅲ类胶合板的要求。     

酶处理对麦秸表面胶合性能的影响

研究麦秸单元经过纤维素酶和半纤维素酶处理后的表面润湿性能、化学基团和胶合强度的变化.结果表明:在试验区间内,随着纤维素酶和半纤维素酶用量的增加,麦秸的表面胶合强度逐渐上升,UF树脂对麦秸表面接触角逐渐减小;酶处理时间的延长,有利于麦秸表面胶合强度的提高.     

绿液预处理麦秆纤维素酶水解的研究

研究了绿液预处理对麦秆酶水解的影响.比较了不同绿液预处理条件下麦秆的浆得率、成分组成与纤维素酶解率,结果表明,预处理条件越剧烈,原料损失越大,而木质素脱除率越高,且在相同酶水解条件下,纤维素酶解率却越高,其中适宜的条件是预处理温度150℃,总碱量8％(Na2O计,对绝干原料)和硫化度40％,浆得率62.0％,葡聚糖、木聚糖和木质素质量分数50.0％、18.9％和16.2％,葡萄糖和木糖得率分别为74.2％和73.5％.考察了质量浓度和酶用量对绿液预处理麦秆酶水解的影响,优化了商品纤维素酶酶系结构和Tween-80的添加量,表明绿液预处理麦秆纤维素酶水解的适宜条件为质量浓度100 g/L,纤维素酶用量15 FPU/g(以纤维素计,下同),β-葡萄糖苷酶9 IU/g,木聚糖酶30 IU/g,Tween-800.05 g/g.在以上条件下,酶水解72 h,葡萄糖得率和木糖得率分别达到了82.5％和77.8％,是优化前的2.6和1.6倍.     

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.