我国竹林生态环境利用研究

根据生态经济学原理，引用阐述竹林生态环境及竹林生态环境利用概念即竹林的地下、地上、林下、林中、林上的全方位立体生态开发利用体系；通过例举大量栽培实例论证了竹林生态环境利用的可行性、实效性及开发前景，论述了竹林生态环境利用的经济、生态、社会、观赏效益的显著与可观，提出创造建立竹、菌、茶、药、食、赏等多位一体复合立体式生态利用系统与最佳生态模式，阐明现有竹林生态环境利用对策与措施，以期逐步形成竹林生产与生态的良性循环和优化复合组合。     

利用世界银行贷款 加快竹业的发展

ImprovingbambooindustlydevelopmentbyusingWorldBankloan我国森林资源十分短缺，木材供需矛盾非常突出。竹子是森林资源的重要组成部分，又是一个极有开发利用潜力的行业。竹子全身都是宝，具有经济、生态和社会三大效益。我国有着发展竹业的良好基础和优越条件，积极争取利用世界银行贷款，改造低产竹林，建立笋材两用竹丰产林基地，进一步搞好竹材加工利用，扩大竹林资源，是一条保护生态环境和生物多样性，促进山区经济发展，使山区群众尽快摆脱贫困走向富裕的可行之路。一、我国竹林资源及生产经营现状1．资源概况中国竹类资源丰富…     

竹类资源加工及其利用前景无限

竹类资源加工的特点 中国是世界竹类资源最丰富的国家。世界有竹类植物50多属、1200多种．中国有40多属、500多种，种植资源竹十分丰富。中国竹林面积居世界第一位．竹林面积达484．26万公顷，（其中经济利用价值较高、集中成片分布的毛竹林面积337．20万公顷）：竹林面积占国土面积0．5％，占森林面积2．8％．毛竹产量7．23亿根，篙竹产量4．29亿根．竹材总产量达11．52亿根。竹类植物具有一次造林成功，科学地加以经营，即可年年择伐．永续利用而不破坏生态环境．这是所有木本植物都不具有的特点。因此开发利用好竹类资源对于促进我国山区经济的发展和维护生态环境都具有重要的意义。     

毛竹林下植被及药用植物调查研究

一,前言竹林环境是一种特殊的生态环境,当前,如何充分发挥竹林的多种效益和用途,越来越受到人们的重视。充分利用这一持殊环境,生产药用植物,开展多种经营,提高竹林经济效益,对发展山区经济具有重要意义。为此,我们对赤水县葫市楠竹场毛竹林下的植被和药用     

竹子纯林经营的林地水分管理

竹子纯林经营方式削弱了竹林水分循环作用,与乔灌木混交竹林相比,其水分循环是不完整的。竹林水分变化又影响到竹林经济效益和生态环境变化。通过对竹子纯林经营水分循环变化的研究,表明乔灌木对竹林起着“引水”和“提水”的作用,是其它各种人工方法都难以取代的,因此建议以科学发展观的态度,从森林群落生态学的角度对竹子混交林的效益、保护、营建、培育等方面开展研究,大力提倡混交林经营。     

竹林生态环境资源分析及旅游开发探讨

长期以来,竹林的旅游开发价值局限在观光游览、科普教育等方面,没有得到深层次的挖掘.森林生态环境资源是当今生态旅游发展的一个重要方向,竹林同样也具有良好的生态环境资源.文章通过理论和实证研究证明了竹林植物精气含量高、空气负离子浓度高的特点,并提出了三点竹林生态环境资源的旅游开发措施.     

农用林──笋用林经济效益分析与发展

目前，在中国南方山地丘陵区广大农民为摆脱贫困，在比较利益驱动下，充分利用房前屋后和自留山的小块分散的土地资源，以市场为导向，积极调整产品结构，发展优质、高产、高效益的笋用竹林。经营笋用竹林的经济效益远大于毛竹用材林和笋竹两用林，内部收益率高达６０％－９０％，效益成本比为２．４－３．２，农户经营笋用竹林的经济收入占农户总收入的３０％－５０％，成为农户经济收入的主要来源之一。凡经营笋用林的农户人均年收入高于当地人均年收入的３５％以上，根据笋用竹林经营特点与农户的意愿，经营形式以农户家庭经营为主，现有经营规模一般不超过０．３５ｈｍ２。提高笋用竹林经济效益的途径是增加科技投入、集约经营和发展产品加工业。因此，在中国南方山地丘陵区，利用分散的小块土地发展笋用林是农户脱贫致富的有效途径。     

试论云南山区竹类资源的合理利用

本文以云南省怒江州作为研究对象，基于充分的外业调查，地其自然社会特点和竹类资源进行了云南山区竹类资源的合理开发利用问题，在此提出并分析了正确评价竹林的地位和作用，遵循竹类资源开发利用的生态经济原则等问题。认为云南山区竹类资源开发利用的对策是：１．大力发展竹林，保护生态环境；２．选准利用方向，实现良性循环；３．多种并举，促进竹业发展。     

商品竹林植物型复合经营理论与实践及其研究进展

为维护商品竹林立地生产力持久发挥和稳定,提高竹林生态系统稳定性和多功能效益,促进竹林高效可持续经营,在分析现行竹林经营中存在的主要问题基础上,按照生态系统综合管理原则,明确了实施竹林复合经营的必要性,介绍了商品竹林复合经营的概念与目标,阐述了竹林植物型复合经营的理论基础及其实践经验,提出了超高产复合经营植物材料选育、高效栽培模式与技术、生态系统稳定性和效益发挥评价等竹林植物型复合经营的重点研究领域与方向。     

开设毛竹山机耕路竹林效益的研究

通过对福建省毛竹林面积最大的乡(镇)迪口镇竹山机耕路开设后产生的效益进行预测分析表明：全镇20．6万亩毛竹林每度竹山产值可增加1341万元。人均收入增加420元。农特产税收入增加70．8万元。林业育林金收入增加43．7万元。达到农民增收、财政增税、部门增费的目的，同时还节约运竹材成本50～100万元。从生产笋干转入直接卖鲜笋后，每度可减少4577m^3薪材资源的消耗。能有效地保护竹林内阔叶树资源。改善竹林生态环境。提高竹林质量。实现竹林可持续经营．     

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.     

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.     

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.     

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.     

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.     

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。