封山育林是培育森林的一种好形式

封山育林是利用森林演替规律,借助自然力,配合人工营林措施,达到恢复森林目的的一种造林方式。在《1989年——2000年全国造林绿化规划纲要》中明确指出:“十二年规划造林总面积5716.5万公顷,其中人工造林3957.9万公顷,飞播造林616.0万公顷,封山育林1142.6万公顷,年均造林面积476.4万公顷”。封山育林的面积占19.99％,可     

封山育林效果好

桂东县把封山育林作为加速全面绿化,发展高效林业,致富于民的一件大事来抓。从1985年至1998年全县共封山100万亩,今年底新增封山22．3万亩。被国家林业局、省林业厅列为封山育林试点县。据调查,全县森林覆盖率由封山前的55．5％上升到67．3％,森林蓄积量由130万立方米增加到320万立方米。同时,经济效益可观。按过去全县每年人工造林5万亩进度推算,100万亩的封山育林需要20年才能完成;按人工造林每亩用工10个计算,可节省劳动力600多万个;按一般人工造林每亩补助15元计算,需要资金1500万元,而这些年用于封山育林的投资只有301万元…     

桐庐县定向封山育林技术措施及成效初报

桐庐县采取分阶段规划，稳步推进定向封山育林，采用人工造林、无林地封育、伐针留阔人工促进、定株抚育间伐封育类型4种主要模式进行定向封育。经过20多年的定向封育，林分质量得到改善，林分的活立木株数比人工造林（补植）增加近50％，针叶林封育可使蓄积量增长33．7％。同时封山育林有利于形成丰富多样的森林植被类型，改善林分结构，增加地表的有机质，从而改良土壤理化性质，改善生态环境。     

多措并举确保三北防护林工程建设成效

三北防护林体系建设工程1978年在咸阳市实施后,咸阳林业建设逐步向多功能、高效益、科学化方向发展,生态环境得到了极大的改善。三北工程实施以来,全市共完成营造林任务39923万亩,其中人工造林36153万亩,封山育林37万亩,截至2008年底,保存人工造林139万亩,保存率为38％,封山育林在封2．8万亩,全市森林覆盖率从工程实施前的14％,提高到目前的23．5％,增加了95个百分点。     

祁连山浅山区封山育林调查：东沟小流域封山育林15年

东沟小流域全封闭封山育林１５年,累计人工植苗造林５５０ｈｍ＾２,天然更新幼树郁闭成林６０ｈｍ＾２,灌木丛恢复成林４０ｈｍ＾２,人工造林郁闭成林１７６ｈｍ＾２,林地面积比封育增加３９．９％,荒山荒地植被盖度增森林覆盖率由封前的４７．０％增长为７１．８％。     

天恋崇山绿盈目 地喜峻岭翠蕴灵——四川宝兴县林业生态建设

四川宝兴县位于四川盆地西部边缘，东邻芦山，西连康定，跨越成都平原与川西高原的过渡带，幅员面积3114km2，是四川西部大熊猫主要生态栖息区。世界第一只大熊猫模式标本即产于宝兴，因此，宝兴被誉为“大熊猫的故乡”。宝兴县实施的天然林资源保护工程、退耕还林工程、野生动植物保护和自然保护区建设工程，使全县森林面积达到193985hm2，其中95％为原始森林，森林覆盖率达70．8％，全县绿化覆盖率81．04％，人工商品林32406hm2，天保工程公益林人工造林16327hm2，封山育林53133hm2，退耕还林3133hm2，配套荒山造林2333hm2，封山育林667hm2，这里生物资源丰富，生物多样性明显，气候湿润，空气清新，环境宜人，空气质量与水质质量达国家Ⅰ级标准。     

建德市保护和发展森林资源责任状

为巩固灭荒成果，保护森林资源，发展高产优质高效林业，如期实现“八年绿化建德”的目标。全市从1995年至2000年规划人工造林12万亩，中幼林抚育6O万亩，封山育林观万亩。到2000年，全市森林覆盖率由现在的71．2％提高到75％以上。城镇绿化覆盖率达到30％以上。公路绿化率95％以上。为保证上述目标的实现，建德市人民政府（以下简称甲方）与各乡、镇人民政府（以下简称乙方）签订本责任状。甲方要求乙方在1995年至20O0年完成下列任务：一、绿化造林1、完成市下达当年计划，人工造林95％以上，封山育林gO％以上，迹地更新95％以上。2、完…     

内蒙古自汉区“十二五”林业发展目标

林业生态体系建没。“十二五”期间，规划完成林业重点生态建设任务6000万亩，其中人工造林2515万亩、封山育林2485万亩、飞播造林1000万亩。到2015年，森林覆盖率达到21．5％，提高1．5个百分点，活立木蓄积量达到14．1亿立方米，年均增长1000万立方米。力争实现“全区生态环境恶化趋势得到有效遏制、治理区全所好转”的局面,     

闲话封山育林

欲使我省大面积宜林荒山荒地在预定时间内逐步绿化起来,除采用人工造林,飞机播种造林等方法外,封山育林也不可忽视。封山育林是我省绿化荒山,恢复森林,投资少,见效快的一项重要措施。其具体做法是在有条件的地方划定区域,施行禁封,从而减少人畜干扰破坏,充分利用林地优越自然条件,依靠树种天然更新的能力,达到恢复森林的目的。采取封山育林的方法恢复和扩大森林面积,较之人工造林及飞机播种造林有其独特的优点。     

林业工程为周至生态建设注入新活力

周至县自然资源十分丰富，森林覆盖率达到67．45％。丰富的森林资源孕育了清纯而久流不断的黑河水资源，使之成为西安市人民供水的生命河。近年来，周至人民举生态建设大旗，为黑河水资源保护做出了重大贡献，已累计人工造林27万亩，封山育林12．16万亩，飞播造林5万余亩，实现了“添林增绿”保水源区生态安全的目标。     

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.     

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。     

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.     

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.