速生杨小径材的优化开发利用

本文概括列举了速生杨在人造板方面的综合利用简况。简单介绍了速生杨的材性以及利用速生杨制造重组木、胶合板、定向结构拆、中密度纤维板、刨花板、单极层积材、人造薄木等木质人遗产品的工艺和部分产品的性能。利用速生杨制造此类木质产品具有良好经济效益和社会效益。     

防潮型中密度纤维板的研制

研究了以脲醛胶为主，三聚氰胺胶为辅制造防潮型中密度纤维板的工艺条件，讨论了热压时间、热压压力、热压温度、施胶量、配胶比例对中密度纤维板物理力学性能的影响。结果表明：配胶比例是重要的影响因子。采用试验所得的优选工艺制得的产品各项指标均达到或优于防潮型中密度纤维板国家标准。     

热压工艺参数对中密度纤维板弹性模量的影响

通过正交实验分析表明,对7 mm中密度纤维板弹性模量最为显著的影响因素为热压温度、热压时间、热压压力、纤维初含水率、闭合速度。再通过单因素实验,最后得出热压工艺的最佳参数为:热压温度170℃,热压时间238 s,热压压力8 MPa,纤维初含水率8%,压板闭合速度9.67 mm/s。研究表明,按照正交实验得出的最佳工艺参数生产中密度纤维板,可适度提高其弹性模量,从而制造出质量更加优异的中密度纤维板。     

中国林业产业(人造板业)创新获奖项目案例(Ⅳ)

1 项目简介该项目是在多年喷蒸-真空热压技术研究的基础上和实施国家林业局科技成果推广项目"厚型中密度纤维板制造技术"中形成的,由南京林业大学和福建龙岩紫金集团永定紫金木业有限公司共同完成.项目针对目前国内缺少厚型中密度纤维板产品及制造技术,重点研究喷蒸-真空热压工艺、蒸汽喷射及真空抽吸系统以及厚型中密度纤维板后期加工技术三个核心问题,研究制造厚型中密度纤维板的最佳工艺参数,通过实验室试验和工业化生产试验,获得自主知识产权,形成了有自己特色的厚型中密度纤维板成套技术(包括工艺和设备),并在工业化生产中推广应用.该项技术可大幅度缩短生产时间,节省能耗,降低成本;产品及制造技术填补国内空白.     

沙柳材中密度纤维板制备工艺及性能研究

本研究使用改性脲醛树脂胶黏剂制备沙柳材中密度纤维板.在预备试验基础上,采用正交试验及单因素试验方法对沙柳材中密度纤维板制备工艺进行了研究.结果表明:在热压温度180℃,热压时间0.6min/mm,施胶量12％,固化剂氯化铵加入量1％或硫酸铵加入量2％的条件下,沙柳材中密度纤维板各项性能较好,但与潮湿状态下使用的纤维板防水性能要求还有一定差距.     

棉秆中密度纤维板工艺技术的研究

探讨以棉秆为原料生产中密度纤维板的主要生产工艺参数.试验结果表明,在板材密度0.7 g/cm3、施胶量12%、防水剂1.5%、热压温度180℃、热压时间15 s/mm的最佳工艺条件下,棉秆中密度纤维板的各项力学性能均超过国家标准要求,但24 h吸水厚度膨胀率未达标,可能与棉秆原料自身特点有关.     

双组份豆粕基中密度纤维板的制备及性能研究

为解决传统中密度纤维板甲醛释放的问题,实验以豆粕粉为原料,研制出双组份生物质基环保型胶黏剂,并用其制备了中密度纤维板。通过单因素法研究了胶液、豆粕粉用量,木纤维含水率及热压时间对豆粕基中密度纤维板物理力学性能的影响。结果表明:1)在热压温度180℃条件下,胶液用量100 kg/m~3,豆粕粉用量60 kg/m~3,热压时间27 s/mm,木质纤维含水率(12±1)%为较优的制备工艺;2)较优条件下制备的中密度纤维板密度(ρ)为760 kg/m~3,内结合强度(IB为0.71 MPa,24 h吸水厚度膨胀率(24 h-TS)为9.3%,静曲强度(MOR)为33.2 NPa,弹性模量(MOE)为3 319 MPa,各项指标均符合国家标准;3)穿孔萃取法测试甲醛释放量为0.2 mg/100 g,优于国家E_0级纤维板标准;4)总挥发性有机化合物(TVOC)的释放率合格,挥发率达到A~+级。     

狼尾草中密度纤维板的研制

狼尾草是多年生禾本科草本植物,易种植、产量高,通常用作动物饲料.综合利用狼尾草原料,不仅可以提高其经济价值,而且可作为一种木材替代原料生产人造板,缓解木材资源紧张的矛盾.本文探讨了用狼尾草制造中密度纤维板的几个工艺因素与板材性能之间的关系,从而确定了较佳的工艺参数.     

制板因素对FRW阻燃中密度纤维板性能的影响

制板因素对阻燃中密度纤维板(MDF)各项性能的影响至关重要.根据前期试验,选取阻燃剂施加量和热压温度两个主要的制板影响因素,分别探讨了该因素对FRW阻燃中密度纤维板物理力学性能和阻燃性能的影响.研究结果表明:阻燃剂施加量对FRW阻燃中密度纤维板的物理力学性能影响较小,并且所有物理力学性能指标均达到并超过了中密度纤维板国家标准GB/T11718-1999的要求;而阻燃剂施加量对FRW阻燃中密度纤维板的阻燃性能影响较大,氧指数与阻燃剂施加量之间具有显著的相关性.热压温度除对FRW阻燃中密度纤维板的几个指标略有影响外,对其他的物理力学性能指标和氧指数几乎无影响.     

纤维板热压中心层温度与力学性能的关系

在不同板材目标厚度、不同板坯含水率、不同热压时间及热压温度条件下压制干法中密度纤维板,并测定板坯中心层在热压过程中的温度变化数据及产品力学性能,比较、分析各条件下中心层的温度与产品力学性能数据,得出了纤维板热压过程中中心层温度与产品力学性能的关系.     

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.     

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.     

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.     

Biogeochemical impacts of clearfelling and reforestation on blanket-peatland streams: II. major ions and dissolved organic carbon

Streams and drains in blanket-peatland forest in western Ireland were sampled weekly over 5 years, 1996–2000, using continuous, depth-proportional passive sampling. Analysis was for pH, alkalinity by Gran titration, anions by IC, metals by ICP, aluminium speciation by loaded-resin exchange, and dissolved organic carbon (DOC) by absorbance at 320 nm.

Effects of felling are identified graphically from two forest drains whose catchments (both about 1 ha) were clearfelled, and partial clearfelling of one larger catchment (somewhat over 1 km²), in summer 1999. Calcium concentrations and alkalinity were increased in the drain- and streamwater from the felled areas. The pH was increased in drains, while in the larger stream, pH range decreased while the mean increased. Phosphorus increased markedly with clearfell, in the absence of recent fertilising, and also increased with fertilising; these results are reported in an accompanying paper. Ammonium-nitrogen concentrations were increased in the two drains with felling, and temporarily decreased in the larger stream. Nitrate increased in some cases. Potassium and manganese concentrations also increased. Concentrations of DOC and organic monomeric aluminium increased gradually, subject to a continuing strong annual cycle. There were no clearfelling effects on concentrations of solphate, suspended solids or inorganic monomeric aluminium. In the two drains (fully clearfelled), concentrations of sodium, chloride and magnesium, and conductivity, were all reduced after felling. Fertilising effects other than for phosphorus were indistinct.

Effects of the combined clearfell–reforestation treatment were testable statistically, using randomised intervention analysis, between two larger streams (1 km²) as a treatment–control comparison. There were statistically significant positive responses in streamwater concentrations of nitrate, potassium, calcium, DOC and aluminium fractions. The implications for management practice depend on whether the loss of nutrients is sustainable for future crop productivity, and whether critical limits and loads of receiving ecosystems are exceeded.     

Effect of Drought on Growth and Mortality of Actively Growing Norway Spruce Container Seedlings Planted in Summer

Survival, root egress and height growth of 13-month-old actively growing Norway spruce ( Picea abies (L.) Karst.) container seedlings exposed to preplanting drying treatments (0, 4, and 8 days) and postplanting drought periods (1, 2, 3, and 4 weeks) were studied in the field between 5 July and 18 August 1999. The mortality of seedlings increased and the height growth and root egress decreased throughout the postplanting drought period. Postplanting performance was also affected by preplanting drying treatments. The results indicate that no risk of excessive mortality and growth restrictions occurs when actively growing seedlings are planted in summer, provided that seedlings are well watered before planting and the drought period does not exceed 3 weeks.     

Rehabilitation of diseased cacao fields in Peru through shade regulation and timing of biocontrol measures

The objective of this case study was to test the effectiveness of biocontrol for the rehabilitation of abandoned, diseased (moniliasis, witches' broom and black pod) cocoa and to develop testable hypotheses regarding the effect of shade and biocontrol timing. Three trial fields differed in their shade regimes. Biocontrol was administered starting either at flowering or pod filling. Disease incidence and yield were compared with cultural control alone. Biocontrol reduced moniliasis from 49% to 25%, independent of the shading regime and application time. Witches' broom was most severe without shade and unaffected by biocontrol. No significant effects on black pod were observed. Although biocontrol increased percentage healthy fruit independent of shading and timing, only the shaded plot with biocontrol from flowering onwards responded with increased yield. Our hypothesis is: 'In the rehabilitation of abandoned cacao, only fields under sustainable shade management and early onset of biocontrol can realise their production potential.' This revised version was published online in June 2006 with corrections to the Cover Date.     

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.     

Growth of Mixed Birch-Coniferous Stands in Relation to Pure Coniferous Stands at Similar Sites in South-eastern Norway

Mean age, mean and top heights and yield were studied in 20 mixed stands of birch ( Betula pubescens Ehrh. and B. pendula Roth) and Picea abies (L.) Karst. and nine mixed stands of birch and Pinus sylvestris L. in south-eastern Norway. Each mixed stand and the adjacent pure coniferous stand (control) were growing under the same site conditions and had not been commercially thinned. There were no significant differences in mean age at breast height or in top heights between birch and conifers in the mixed stands, while mean height was significantly higher for birch than for spruce. A growth index was calculated based on total volume and age at breast height. For the spruce sites the growth in young mixed stands (birch < 17 m) was superior to that of pure spruce, while the difference was insignificant in older stands. The growth index correlated positively with the ratio between generatively and vegetatively regenerated birch trees, and negatively with the age of the oldest species in the mixture and with site quality. For the pine sites there was no significant difference in the growth index between mixed birch-pine and pure pine stands. A mixture effect of birch on the volume yield of spruce or pine could not be demonstrated.     

Defoliation by the Needle-shortening Pine Gall Midge,Thecodiplosis brachyntera,on Pines in Central Sweden

An outbreak of the needle-shortening pine gall midge, Thecodiplosis brachyntera , occurred on Scots pine, Pinus sylvestris (L.) and lodgepole pine, P. contorta (Dougl.) in central Sweden during 1995-1998. The larval feeding of T. brachyntera kills current-year needles and heavy infestation causes severe defoliation. A pattern of fluctuating defoliation among years and sites was found on both pine species. Defoliation was evenly distributed in the crown of P. sylvestris during years of high as well as low infestation; apical whorls had as much defoliation as basal whorls. In P. contorta , however, there was a tendency for defoliation to be concentrated on branches in the most apical whorls. Growth ring increments on P. sylvestris with high levels of defoliation (71%) did not differ from trees with moderate levels (26%) of defoliation. Shoot lengths were significantly shorter, however, on heavily infested trees the year after defoliation.