湿地松板材脱脂技术试验研究

采用正交试验方法研究了湿地松脱脂技术。研究表明 ,影响脱脂综合指标的因素主要有 :脱脂液浓度、温度、处理时间、水与木材的体积比。当浓度为 0 5 %,温度为 80℃ ,处理时间为8h ,水与木材体积比为 4时 ,脱脂处理后综合指标最高。经脱脂处理后力学性能降低较小 ,色泽变化不大 ,也不需另外对湿地松进行脱松节油处理 ,即可作家具或装潢材料使用。     

竹材氨法木质素高效分离试验

本文研究了利用氨水作为蒸煮液对天然原料竹材中木质素的高效分离作用,并探讨了在不同氨水浓度,液固比,最高反应温度,最高反应温度下保温时间等条件对氨水分离竹材中木质素的影响,研究结果表明:当氨水浓度为25%,液固比为6:1,最高反应温度为180℃下保温3 h,氨水对竹材中木质素的分离效果最佳.并就反应得到的氨黑液的资源化利用提出自己看法.     

马尾松毛虫幼虫蛋白质的提取及产品营养和安全评价

采用缓冲液法对马尾松毛虫幼虫中的蛋白质进行提取研究.结果表明:原料粗细度、提取温度、提取时间和沉淀pH对幼虫蛋白质的提取率有显著影响(P＜0.05),而料液比、蛋白质的沉淀温度和沉淀时间对提取率无显著影响.试验确定的最佳条件为:缓冲液为Na2 HPO4-NaOH(pH为9.5);料液比为1:15(m/v);原料粗细度为40目虫粉;抽提时间为5 h,抽提温度为40℃;沉淀pH为5.0,沉淀温度为5℃,沉淀时间为1 h.在此条件下,所得蛋白产品的粗蛋白含量为(71.12±0.16)%,总氮提取率为(60.36±1.25)%.蛋白产品中氨基酸总量为69.58%,必须氨基酸占氨酸总量的45.16%.安全评价结果表明:该蛋白产品的LD50在12050 mg·kg-1以上,属实际无毒范围.     

湿地松松木板的脱脂

对汨罗市桃林林场湿地松材试样进行脱脂工艺的研究.选择适宜的化学试剂,并以反应浓度、温度、时间等工艺条件对脱脂的影响进行探讨,通过正交设计试验,综合考虑其它几方面因素,筛选出较好的工艺条件为:浓度1%、温度120℃、时间3h.其脱脂效果良好,木材表面无溢脂现象,达到脱脂要求.     

超声波辅助提取沙棘果渣中的粗多糖

研究了超声波提取时间、固液比和提取温度等因素对多糖提取量的影响,并通过正交试验得到了超声波提取沙棘果渣多糖的最佳工艺参数为:超声波提取时间20 min、固液比为1 g:50 mL、提取液温度为60℃,在此条件下沙棘多糖的提取量为88.09 mg/g.     

巨尾桉化学改性预处理工艺

为了更好地利用桉木木素进行化学改性,须有效去除桉木中的其他组分。通过单因素试验和正交试验,研究了巨尾桉改性前预处理工艺,确定桉木纤维脱脂处理溶剂为苯-乙醇(V/V,2∶1),最佳提取条件为:时间为4 h,温度66℃,固液比为1∶15。对处理前后的桉木纤维进行了性能表征,结果表明:处理后桉木纤维素酶解较处理前还原糖得率和水解率均有所提高;灰分含量降至0.09%,小分子有机化合物含量≤1%。     

水竹叶总黄酮的提取及纯化工艺研究

以水竹叶为原料,采用水浴和超声波两种提取方法,通过单因素与正交试验确定了水竹叶总黄酮提取的最佳条件,并筛选了不同树脂对总黄酮的吸附和解吸附特性.实验结果表明:水浴提取最佳条件为:温度50 ℃,提取时间2.0 h,乙醇体积分数60%,固液比1:20(g:mL,下同);总黄酮得率1.65%.影响得率的因素为:固液比＞乙醇体积分数＞提取温度＞提取时间.超声波提取最佳条件为:2.0 g水竹叶,超声波作用时间30 min,乙醇体积分数60 %,固液比1:15;总黄酮得率为1.27%.影响得率的因素为:超声波作用时间＞乙醇体积分数＞固液比.AB-8树脂对总黄酮纯化具有较好效果,体积分数为70%的乙醇是较好的解吸剂.     

竹粉的稀硫酸预处理及酶解技术研究

采用稀酸对竹粉进行预处理,结果表明竹粉酶解的最佳优化条件为:温度125℃,固液比最佳比值为1:10,硫酸浓度为4%,预处理时间为2 h,经过酶处理以后,其竹粉水解率达57.99%,半纤维素水解达70.18%.     

沉香叶中芒果苷的提取工艺

以沉香叶为原料,采用单因素试验和正交试验,探讨乙醇浓度、液固比、提取时间和提取温度对芒果苷提取率的影响,并以提取率为评价指标,优化提取工艺。试验结果表明,沉香叶中芒果苷的最佳提取工艺为:采用体积分数70%的乙醇,液固比20,提取温度90℃,回流提取2次,每次1h。在此优化工艺条件下,芒果苷得率达3.31%。     

减压内部沸腾法提取壶瓶枣多糖及其脱色工艺的研究

对减压内部沸腾法提取壶瓶枣多糖及其脱色工艺进行了研究。以蛋白质和多糖得率为指标,通过正交试验优化得到的最佳工艺条件为:体系内温度60℃,液料比为20∶1(m L∶g),时间为30 min,此时真空度为80 k Pa,外界温度为70℃,蛋白质和多糖得率分别为0.13%和2.60%。与传统热浸提相比,其得率分别提高了18.18%和23.22%。对10种脱色材料的筛选结果表明D900型大孔吸附树脂是理想脱色材料,通过正交试验优化得到的D900型大孔吸附树脂脱色优化工艺参数为D900添加量3.5%,时间20 h,p H值11.7,温度40℃,此时脱色率、脱蛋白率和多糖保留率分别为81.94%、38.19%和87.42%。     

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.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

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。     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.