山区列发中经济林持续发展的思考

在山区林业综合开发中，各地把发展经济林作为振兴山区经济，引导农民致富的“突破口”，但是如何使经济林得到持续发展，需要思考两个问题，一是建造人工防护体系，以促进和保障经济林基地的发展；二是转变经济增长方式，以适应市场经济条件下经济林产品的营销。     

生态经济林与可持续发展

通过实地调查与资料收集，对生态经济树种及生态经济林进行了定义，分析了我国经济林的生产现状及发展生态经济林的意义。介绍了浙江省杨梅、山核桃、山茱萸、香榧等主要生态经济树种的经济效益与生态效益，并探讨了生态经济林纯林、混交林、立体经营及散生庭院式的栽培模式及规范化栽培，指出山地或坡地发展生态经济林应以混交林和立体经营为主，减少纯林栽培，提倡四旁、宅院种植经济林以增加收入、美化环境。同时指出生态经济林也是经济林生存和持续发展的根本问题。     

新绛县达到人均四分经济林

新绛县达到人均四分经济林山西省新绛县结合本县实际，积极推广、普及经济林。截止目前，全县已发展经济林１０多万亩，全县农民达到人均四分经济林。新绛县地势平坦，是晋南盆地平原，以种植粮棉为主，是个典型的纯农业县份。从去年开始，县委、县政府把发展经济林作为全...     

彰武县经济林建设现状及发展对策

为促进彰武县果品经济林建设上规模、提水平、增效益,加快"果品经济林示范带"建设的步伐,提出果品经济林发展要以市场为导向,以科技创新为动力,以"三效合一"为中心,按照发展县域经济、特色果品经济和建设果品经济林精品工程的要求,优化布局、适地适树,加快现代农业产业化步伐。对彰武县经济林发展现状进行了调查,分析了经济林发展现状、特点和存在问题,提出了彰武县经济林发展对策。     

建设绿色产业 振兴农村经济——西峰市发展林果业的调查

建设绿色产业振兴农村经济——西峰市发展林果业的调查本刊特约记者尉祖庚西峰市委、市政府以增加农民收入、培植财源、保证经济持续、稳定、健康发展为目标，立足自然优势，把以苹果为主的经济林开发建设作为支柱产业，倾斜扶持，大力发展。经济林开发建设已成为西峰市农...     

关于我区低产经济林改造的问题

近几年来，在社会主义市场经济的驱动下，我区农村以林果致富的势头有增无减，经济林发展迅速。预计今后数年内仍呈继续增长的势头，到1995年面积已达310万亩左右。适宜农民经营的经济林，带动了农村地方经济的全面发展，产生了明显的经济及社会效益。但不容忽视的是，由于生产技术落后，管理工作粗放，信息不灵，品种更新换代慢，规划布局不当，管理体制不顺，加之必要的投入资金不足，低产经济林比重大，如不尽快采取措施加以解决，必将严重阻碍经济林的健康发展，给农村奔小康带来不利影响。下面，笔者就南疆21个县市经济林的情况调查，…     

安徽省经济林产业现状及发展对策

多效的经济林建设适合安徽省省情，并已成为发展安徽省农村经济的重要支柱产业之一。安徽省经济林建设应以生产基地为主要形式，以加工企业为行业龙头，实现标准化生产，品牌推动战略，走产业化发展的道路。     

浅析经济林标准化促进产业化发展

经济林及其产业概述经济林是以生产果品、食用油类、饮料、调料、工业原料和药材等非木材为主要目的的林木。经济林以其产品众多、用途广泛,并可增收创汇而被人们认为是我国经济效益、生态效益、社会效益统一得较好的重要林种。实践证明,发展山区经济潜力在山,希望在林,突破口在经济林,也可以说,经济林是山区发展经济的重要林种,经济林自身也是林业生态建设的部分。在西部大开发中,发展经济林对改善生态环境和农民致富都具有重要意义。经济林发展的总趋势是产业化,基地化和现代化。经济林产业化就是以市场为导向,以经济效益为中心,以主导产…     

经济林产品国内外市场需求预测（1996－2010年）

随着世界经济的持续发展和对外贸易的日益扩大，经济林产品已经成为世界各国发展经济和扩大对外出口的主要产品。通过对影响经济林产品市场需求的要素分析和对经济林产品市场供求状况的回顾，对来来１５年（１９９６－２０１０年）国内外经济林产品市场需求进行了预测，并对当前经济林发展存在的问题提出调整设想。     

黑龙江省发展生态经济林探讨

从生态经济林概念提出、发展阶段入手，结合生态文明建设理念和黑龙江省林业资源条件，特别是结合林下经济对黑龙江省经济发展和林草事业发展的重要作用，尝试对生态经济林的概念进行了扩展与讨论。提出黑龙江省发展生态经济林的原则、基础性工作，并对林业科研支持生态经济林建设的研究方向进行了分析。在此基础上，提出了黑龙江省生态经济林发展建议。     

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.     

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。     

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.     

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.     

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.