关于建水县沼气后续服务体系建设的思考

指出了沼气建设是社会主义新农村建设的重要内容,也是保护农村生态环境、实现农业可持续发展的重要保障。分析了建水县农村沼气后续服务的现状与存在的问题,并提出了解决措施,为促进建水县沼气事业的健康发展提供参考。     

以沼气为纽带 建设生态家园——全区农村生态家园建设电视电话会议

全区沼气生态家园建设电视电话会于10月8日在南宁召开，自治区副主席陈章良在会上强调，以沼气为纽带，建设生态家园，是建设社会主义新农村的保障，要深入贯彻落实科学发展观，认真分析沼气建设面临的新形势、新任务、新问题，提升沼气技术，创新发展模式，加强管理服务，又好又快地推进农村沼气生态家园建设，保质保量按期完成今年全区新建20万座沼气池这件为民办的实事，向自治区成立50周年大庆献礼，为发展循环经济、推进节能减排、建设社会主义新农村作出新的贡献。     

高温太阳能集热系统在沼气池内发酵增温的应用

针对湖南地区冬季气候寒冷、沼气池不产气的问题,结合该地区太阳能资源丰富的特点,将太阳能中高温集热装置和沼气发酵装置进行了组合,设计了一套新型的太阳能加热的沼气生产增温系统.该系统可以满足业主全年对沼气以及生活热水的需要,从而改善农村人居环境和生态环境,缓解农村生活用能和工业用能之间的矛盾,实现节能减排,加快社会主义新农村建设步伐,建设和谐的社会主义新农村有重要示范推广价值和重大社会经济意义.     

崇阳县发展农村沼气存在的问题与对策

指出了随着我国社会经济的不断发展,绿色生态农业引起了越来越多人的重视,农村沼气对促进农业增效、农民增收和新农村建设有着重要的影响。分析了崇阳县沼气建设现状,针对崇阳县沼气发展中存在的问题,就如何大力发展农村沼气,提出了一些对策与建议。     

新农村建设背景下农村沼气建设可持续发展的探讨

指出了沼气建设已经成为了中国能源发展战略的重要内容,是解决能源资源短缺、环境污染严重的必由之路,在具体的建设中已取得了举世瞩目的成效,为可持续发展的道路做出了贡献。在新农村建设背景下,针对农村的沼气建设发展的现状,分析了其现存的问题,以保证农村的生活富裕、生产发展为切入点,为农村沼气建设可持续发展提出了对策建议,以期能更加适应新农村发展。     

中国农村生物质能源发展现状与展望

我国是农业大国,生物质能源作为我国农村生活用能的重要组成部分,其开发利用对保障国家能源安全和社会主义新农村建设具有重要意义。文章分析了我国农村生物质能源的发展现状和消费结构,认为我国农村地区的生物质能利用主要集中在沼气、秸秆和薪柴。近几年来,我国沼气利用的规模不断扩大,秸秆利用方式由传统的燃烧向集中制气、炭化和固化成型等多种方式转变。农村生物质能源消费以秸秆和薪柴为主,沼气在消费结构中所占比例呈上涨趋势。当前我国生物质能源的利用仍存在许多问题,未来应从生物质能资源清查、技术、政策资金保障、市场以及产业发展等方面促进农村生物质能源的开发利用。     

用沼气代薪柴保护森林植被

农村沼气的大力发展，不仅解决了农村的生活用能，而且拉动了养殖业的发展，许多农民已经从使用沼气池的实践中认识到：发展沼气池是保护生态的需要，是文明家居生活方式的需要，要积极参与到森林资源保护和生态建设中来，这对广大农村生活环境改善、乡风文明及社会主义新农村建设起到了重要的促进和推动作用。     

集体林权制度改革与建设社会主义新农村的探讨

文章紧紧围绕社会主义新农村建设的核心是发展生产力这一主题,从集体林权制度改革是解放农村生产力的突破口和深化配套改革是林业更好服务新农村建设的着力点两个方面进行论述。抓住八个着眼点,全面阐述了以集体林权制度改革为核心的综合配套改革,解决了长期以来林业工作中乃至整个农村工作中没有解决好的许多困难和问题,有效调整了林区的生产关系,有力激发了农村和林业生产活力,为农村经济社会的长效发展找到了出路,为创新农村工作机制、解决"三农"问题、促进社会主义新农村建设起到的重大作用。     

农村制度环境变迁对山东省新农村建设的影响

社会主义新农村建设是在我国全面建设小康社会、加速向现代化迈进的关键时期以及在总体上进入"两个反哺"的新阶段提出的,分析了影响新农村建设的因素,从制度层面出发,探讨了农村制度变迁对山东省的新农村建设的影响,以期能够对农村的发展以及政策的制定有所帮助.     

发展沼气 改善农村能源结构——沼气池在新农村建设中的重要作用

社会主义新农村建设是我国现代化进程中的重大历史任务,在新农村建设中,农村基础设施是农村经济社会发展和农民生产生活改善的重要物质基础。加快发展农村能源,是加强农村基础设施建设的主要内容,是促进生态保护、发展循环经济的重要途径,也是社会主义新农村建设的重要内容。     

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.     

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.     

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。