造林方式对油松造林效果的影响

为探索适合辽西半干旱区油松的最佳造林方式,对容器苗造林、塑料袋保苗造林、裸根造林3种方式进行比较试验。结果表明:容器苗造林方式下苗木保水性好,造林的成活率及保存率最高,造林的成本显著低于裸根造林;塑料袋保苗造林方式下苗木的保水性、成活率等均好于裸根造林方式,其造林成本最低。     

工程造林应走差别化之路

工程造林由于投资、管理方式和造林积极性等不同,造林成效明显不同。在安排工程造林时应从造林积极性、投资、管理等几个方面进行考虑,走差别化造林之路,提高造林成效,增加绿化面积。     

林苑短波

正邢台市全面完成春季造林任务今春以来,邢台市抢抓春季造林有利时机大打造林绿化攻坚战,超额完成了市下达的造林计划。截至4月1日,全市共完成造林59.06万亩,占春季造林任务的105.8%。其中山区生态经济示范区造林4.04万亩,山区结构调整造林10.06万亩,村庄绿化造林4.17万亩,道路绿化3.74万亩,农田林网造林1.92万亩,河渠绿化造林5.84万亩,其它造林29.3万亩。主要呈现出六个特点:一是领导重视程度高。市委、市政府高度重视造林绿化工作,今年全面启动了创     

承德县十大举措推进个体造林

在中央《决定》放手发展非公有制林业政策的感召下,承德县个体造林如雨后春笋般蓬勃发展。承德县1990年造林12万亩,其中个体造林333．33公顷,占造林任务的4．1％;2000年造林9500公顷,个体造林7．2万亩,占造林任务的51％;2004年造林22万亩,个体造林1．47万公顷,占任务的82％;2007年造林任务5667公顷,全部为个体造林。个体造林的快速发展,是林业建设史上体制改革的新突破,必将成为促进林业发展的新亮点。     

植树造林的几种方法

<正>一、直播造林法直播造林法是将林木种子直接播种在造林地进行造林的方法。这种方法省去了育苗工序,而且施工容易,便于在大面积造林地上进行造林。但是这种方法造林对造林立地条件要求较严格,造林后的幼林抚育管理措施要求也较高。播种造林的适用条件:适合于种粒大、发芽容易、种源充足的树种,对于边远且人烟     

河西走廊北部风沙区困难立地造林试验

张掖市甘州区兔儿坝滩是河西走廊北部生态屏障的重要地段,气候干旱,造林立地条件差,加之技术措施单一,导致多年造林成活率、保存率很低,为此,选择具有代表性的地段进行了河西走廊北部风沙区困难立地条件造林试验,结果表明,相同条件下,顶凌造林可提高造林成活率10～20个百分点,截干造林与全苗栽植相比,造林成活率提高10个百分点。因此,在干旱困难立地条件下造林,综合应用抗旱造林技术,不但可提高造林成活率,而且造林效果明显。     

南方红豆杉山地造林的坡向和苗木类型选择

坡向是影响南方红豆杉造林成活率和造林质量的重要因素,造林以选择阴坡或半阴坡为优,并且以2年生幼苗造林效果较好。此处,宿土苗春季造林成活率和秋季造林成活率都极显著高于裸根苗造林。     

阿拉善地区梭梭秋季造林试验

在阿拉善左旗境内选取5个试验区,观测不同时期春季造林和秋季造林新梢生长长度、地径大小、冠幅大小及苗木成活率。结果表明:各试验区内春季造林和秋季造林苗木生长量和成活率的表现规律较一致;春季造林,苗木在进入生长季后,生长缓慢,到6月后,生长速度开始加快,但与秋季造林的苗木生长量差异显著(P0.05),秋季造林苗木生长量显著高于春季造林生长量,而且,秋季造林成活率也显著高于春季造林成活率。因此,本地区适宜秋季造林。     

干旱区抗旱造林技术探析及其应用

抗旱造林技术需要因地制宜,其整地方式、造林方法、护林方法等都有着不同程度的差异。选择合适的造林方法与造林技术进行科学造林有利于提高造林成活率。分析我国的抗旱造林技术及其相关技术要点,旨在为我国干旱地区抗旱造林提供一些参考思路。第一部分论述了抗旱造林技术研究的背景及意义,第二部分分析了抗旱性树木的选择,第三部分论述了抗旱造林技术,第四部分探讨了抗旱造林技术要点,第五部分以辽西北地区为例,论述了抗旱造林技术的应用。     

关中地区常用植树造林方法

一、播种造林法播种造林又称直播造林,将林木种子直接播种在造林地上,省去了育苗工序,施工容易,便于大面积造林。但这种方法对造林立地条件要求较严格,造林后的幼林抚育管理措施要求也较高。播种造林适合于种粒大、发芽容易、种源充足的树种,如橡栎类、核桃、油茶、油桐和山杏等大粒种子,要求造林地土壤水分充足,各种灾害性因素较轻,对于边远且人烟稀少地区的造林更为适用。播种前的种子处     

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.