异氰酸酯胶在刨花板中的应用

异氰酸酯胶作为刨花板胶粘剂，具有刨花含水率适应范围广（０～２５％），施胶量低、无游离甲醛释放、适合制造轻质刨花板等优点。施胶量为５％、密度为０．４５ｇ／ｃｍ３和０．６１ｇ／ｃｍ￣３的二苯基甲烷二异氰酸酯（ＭＤＩ）小黑杨刨花板的物理力学性能分别达到Ａ类刨花板二等品和优等品的指标要求。密度为０．６５ｇ／ｃｍ￣３时，只要ＭＤＩ施胶量达到３％，刨花板的物理力学性能指标能达到Ａ类刨花板的国家标准要求。试验还表明：ＭＤＩ具有较好的耐水性，但耐湿热性和长期耐水性不如酚醛胶。生产１ｍ￣３刨花板ＭＤＩ与ＰＦ和ＵＦ胶粘剂成本比为２．０５：１．７８：１．００。     

麦秸人造板胶合机理的研究

测定了麦秸表面的自由能以及异氰酸酯（ＭＤＩ）和脲醛树脂（ＵＦ）胶粘剂对麦秸表面的接触角，并用差示扫描量热法（ＤＳＣ）研究了这两种胶粘剂与麦秸之间的热反应特征。其结果表明：麦秸表面的自由能较低；ＭＤＩ与ＵＦ相比，前者对麦秸有较好的润湿性能。ＭＤＩ自身的热反应特征平稳，它可以与水发生反应。研究还表明，ＵＦ和改性ＵＦ相比，两者热反应特征明显不同，后者的吸热反应较前者提前，总吸热量减少。     

山杨二元材积模型的研究

山杨二元材积模型的研究陈东来，秦淑英（河北林学院林学系保定０７１０００）关键词山杨，二元材积模型，拟合中图分类号Ｓ７５８．５１ＡＳＴＵＤＹＯＦＳＴＡＮＤＡＲＤＶＯＬＵＭＥＭＯＤＥＬＳＦＯＲＰＯＰＬＡＲ（ＰＯＰＵＬＵＳＤＡＶＩＤＩＡＮＡ）ＣｈｅｎＤｏｎ...     

森林气候生产潜力研究

森林气候生产潜力研究李建国（中国林科院林业研究所，北京１０００９１）关键词森林，气候生产潜力，估算模型中国分类号Ｓ７１６．３ＳＴＵＤＩＥＳＯＮＰＲＯＤＵＣＴＩＯＮＰＯＴＥＮＴＩＡＬＯＦＦＯＲＥＳＴＣＬＩＭＡＴＥＬｉＪｉａｎｇｕｏ（Ｒｅｓｅａｒｃｈｌｎ...     

不同方法预估未来直径分布的精度分析

不同方法预估未来直径分布的精度分析陈东来，秦淑英（河北林学院林学系保定０７１０００）关键词预估，直径分布，精度分析分类号Ｓ７５８．５３ＳＥＮＳＩＴＩＶＩＴＹＡＮＡＬＹＳＩＳＯＦＤＩＡＭＥＴＥＲＤＩＳＴＲＩＢＵＴＩＯＮＦＯＲＤＩＦＦＥＲＥＮＴＦＯＲＣＡ...     

柿树芽接方法和时期对嫁接成活率的影响

柿树芽接方法和时期对嫁接成活率的影响朱梅玲，乔进春（河北林学院经济林系保定０７１０００）关键词柿树，芽接方法，芽接时期，嫁接成活率中图分类号Ｓ６６５．２ＥＦＦＥＣＴＳＯＦＢＵＤＧＲＡＦＴＩＮＧＭＥＴＨＯＤＡＮＤＴＩＭＩＮＧＯＮＴＨＥＳＵＲＶＩＶＡＬＲ...     

核桃冬季室内嫁接育苗技术的改进

核桃冬季室内嫁接育苗技术的改进韩德章王桂英刘水平王世玲（涞水县苗圃场,０７４１００）（涞水县林业局）关键词核桃;室内嫁接;冬季;育苗技术中图分类号Ｓ６６４．１ＴＥＣＨＮＩＱＵＥＩＭＰＲＯＶＥＭＥＮＴＯＦＷＡＬＮＵＴＳＥＥＤＬＩＮＧＰＲＯＤＵＣＴＩＯＮ...     

土壤中钾含量的测定方法

土壤中钾含量的测定方法任丽江，康明（河北林学院基础部保定０７１０００）关键词钾素，定量测定，土壤分类号Ｓ１５８．２ＤＥＴＥＲＭＩＮＡＴＯＮＭＥＴＨＯＤＳＦＯＲＳＯＩＬＰＯＴＡＳＳＩＵＭＲｅｎＬｉｊｉａｎｇＫａｎｇＭｉｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＢａ...     

搞好“双增双节”的实践意义及其措施

搞好“双增双节”的实践意义及其措施刘达（河北林学院财务科，保定０７１０００）关键词双增双节；市场经济；经济效益中图分类号Ｇ６４７．４ＴＨＥＩＭＰＯＲＴＡＮＣＥＯＦ″ＤＯＵＢＬＥＩＮＣＲＥＡＳＥＡＮＤＤＯＵＢＬＥＲＥＴＲＥＣＨＭＥＮＴＳ″ＡＮＤＴＨＥＩ...     

浅析中纤板生产线的节能工作

节约能源、有效地利用能源，是国民经济和社会发展中一项长远的战略方针，同时也是企业降低生产成本，提高市场竞争能力的必要手段。据最近有关方面报道，我国单位产值能耗是世界平均水平的４．８倍。在我国中密度纤维板（ＭＤＦ）行业中，单位产品综合能耗一级节能企业标准为 ３６５ｋｇ标煤／ｍ３，这一数值已是历史的标准，与当今国际同行相比存在着相当大的差距。据目前国内ＭＤＦ节能先进企业年度统计结果，ＭＤＦ单位产品综合能耗已降至 １８２ｋｇ标煤／ｍ３以下，典型值为 １６３ｋｇ标煤／ｍ３，接近国际同行的先进水平。 总的看，…     

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.     

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.     

Boron in forest trees and forest ecosystems

This review critically examines the role of boron (B) in forests in view of recent findings on B nutrition and the continuing occurrence of B deficiency. Many perceptions about the role of B in plants and its uptake and mobility have been altered since the last review on B in forest trees in 1990. Now there is evidence for a fundamental role of B in the formation of the pectic structure in primary cell walls in plants, and further roles in membrane function are being explored. In plants, channel-mediated B uptake, active B uptake and B uptake by mycorrhizas have been shown, B transporters have been identified, and B retranslocation has been shown. We explore these findings and their consequences on forest trees and on ecosystems that they dominate. Particular emphasis is placed on B retranslocation and B in mycorrhizal symbiosis, given their importance in trees.     

Survival and Growth of Picea abies Regeneration after Shelterwood Removal with Single- and Double-grip Harvester Systems

Three stands in Sweden were followed for 7 yrs to study the survival and growth of Norway spruce [Picea abies (L.) Karst.] regeneration after shelterwood removal with single- and double-grip harvester systems. The height of all seedlings within circular plots was recorded before and after final cutting. The tallest seedling and one randomly selected seedling on each circular plot were permanently marked and their annual height growth was measured each year during the period 1993-1999. No significant differences between single- and double-grip harvester systems were found with respect to their effects on regeneration density, survival or annual height growth. The annual height growth of the individual seedlings after shelterwood removal was significantly correlated with seedling height before shelterwood removal. Significant differences were found in annual height growth between seedlings with high and low vitality. Logging damage did not affect the annual height growth. Several practical conclusions were drawn. First, the choice of harvester system does not affect seedling height growth or survival after shelterwood removal. Secondly, the removal of a 200 m³ shelterwood with 200 stems ha^-1 does not seem to constitute a serious problem for seedling survival and growth. Finally, estimated vitality and seedling height both seem to be fairly good predictors of postrelease survival and growth.     

Development of Pinus sylvestris Main Stems Following Three Different Precommercial Thinning Methods in a Mixed Stand

Reducing competition by point cleaning may be an attractive alternative to conventional precommercial thinning in forestry. In this study, survival and development of main stems of Scots pine (Pinus sylvestris L.) following point cleaning were examined in a mixed stand of mainly Scots pine and birch (Betula pendula Roth and Betula pubescens Ehrh.) in northern Sweden. Treatments studied were: no precommercial thinning, conventional precommercial thinning, point cleaning of all secondary stems, and point cleaning of only the secondary stems that were higher than the main stem, within a radius of 0.8 m from the main stem, respectively. A randomised complete block design with three replicates was used. Measurements taken 13 growing seasons after these treatments showed that conventional precommercial thinning was the best treatment for retaining Scots pines as main stems. However, conventional precommercial thinning resulted in the poorest timber quality of the remaining Scots pines in terms of stem taper, thickest branch diameter and relative live crown height. In conclusion, point cleaning has to be followed by a complementary cleaning operation if the objective is to retain Scots pines as main stems in such mixed stands.