双切嫁接提高板栗春接成活率

双切嫁接提高板栗春接成活率湖北省宜昌市林校刘湘林等采用双切嫁接法进行板栗春接，与劈接、切接、三刀切接对比，成活率分别为９２．８％、６５．２％、７２．０％、８１．２％。通过对嫁接后不同日期萌芽株数、嫁接成活率、成活初期抽梢长度、当年抽梢长度、粗度进行统...     

苹果双砧嫁接技术

苹果双砧嫁接技术杜合金苹果嫁接一般多采用单砧嫁接。近几年来，我们采用苹果种子春季点播，夏季嫩枝双砧嫁接，接后７天芽可萌生，成活率９８％以上。当年新梢生长可达１ｍ以上，且抽枝整齐、粗壮、根平发达，比单砧嫁接高生长增加２一３倍。１播种清明前（３～４月），...     

改进柿树嫁接技术的经验

改进柿树嫁接技术的经验山东省莱西市职业中专林果教研室于新刚等在总结传统嫁接技术的基础上，改进嫁接方法，使柿树嫁接成活率达到９８．２％。（１），嫁接时期的改进。传统的枝接时间在砧木萌芽期，接穗处于萌动状态，一般在４月１０日左右。若在４月２３日砧木芽萌发...     

提高酸枣接大枣嫁接成活率的研究

试验结果表明,选用质量浓度为１００ｍｇ／Ｌ的ＡＢＴ１号生根粉,可使酸枣接大枣成活率提高６１．２％,当年新梢生长量比对照提高８２．６％,在庆阳地区嫁接时间以４月上旬为宜,嫁接后的综合管理对提高成活率也有一定的影响。     

酸枣嫁接大枣技术

在酸枣上嫁接大枣，可充分利用野生资源及塄坎边畔、荒坡等闲散土地资源，提高经济效益。而且接好的枣树具有生长快、结果早（春季嫁接的当年就可结枣）、耐旱、耐寒、耐盐碱的特性。现将该技术介绍如下。１　嫁接时间嫁接一般采用劈接，劈接的最佳时间是从惊蛰到谷雨，即３月上旬到４月下旬。２　砧木与接穗的准备砧木选用无病虫害、生长健壮、有一定粗度的酸枣。如密度过大，需每隔一定距离（坡地、塄坎２ｍ，缓坡地２．５～３．０ｍ）保留和培养酸枣苗，清理砧木萌蘖和周围杂草。主干细的，在嫁接前的生长季节初期摘心，促进径生长。坡地…     

核桃室内枝接、大田育苗技术

陕西省镇安县林业部门连续两年进行了核桃室内枝接、大田直接培育实验，其成活率可达６７％以上。一、嫁接时间：当地的嫁接时期为３月１５日—４月１０日，其中最佳时期为３月２０日—４月５日。二、嫁接方法：双舌对接、劈接法都可以，所不同的是双舌对接接穗要长些，为８—１０厘米，不论哪种方法嫁接，绑扎必须严密不留缝。劈接法的接穗长５厘米左右，单芽，接穗下端削成楔状，长斜面长２．５厘米，短斜面长１．５厘米以内，两个斜面对称。砧木的剪切：从地径处剪去砧木上部苗干，然后从砧木剪口的２／３处垂直纵切，纵切深度在２．５厘…     

胡杨嫁接试验成功

胡杨嫁接试验成功胡杨，主要分布在我国内陆西北地区，耐盐碱性极强。据新疆资料，能在土壤含盐量０．８６％～１．０％的立地上旺盛生长。山东省自五十年代以来，曾多次引进胡杨种子，进行播种育苗及造林试验。在山东，胡杨苗期生长缓慢，当年苗，高者仅达１～２ｃｍ，低...     

枫杨作砧快速营建核桃良种采穗圃技术研究

以枫杨为砧，对核桃进行了嫁接时期、嫁接方法、接穗处理等试验研究，其高改嫁接７０３株，株成活率达９５．２％，接穗成活率达７０．９％。当年亩产接穗比以核桃为砧改接核桃采穗圃产量高２．１６－３．４８倍，具有成本低、见效快、质量好的特点。９４年已通过省级成果鉴定。     

芳樟醇型樟树嫁接育苗试验

以芳樟醇含量92％以上，樟脑含量低于0．2％的优良樟树品系为对象，取当年生枝条及1～2年生枝条为接穗，一年生实生苗为砧木，分别用切接、劈接、舌接不同方法、春、夏、秋不同季节、不同接穗组合进行嫁接试验。试验结果表明，在不同季节的嫁接试验中，冬季嫁接成活率最高；在最适合嫁接的冬季，当年萌发的枝条嫁接存活率较高；当年生枝条用切接法，1～2年生枝条舌接成活率较高。     

河北杨、毛白杨休眠期嫁接育苗技术试验

对河北杨、毛白杨进行休眠期嫁接试验，结果表明：室内嫁接工作从元月１０日开始至砧木和接穗的芽未萌动期间均可进行。砧、穗结合体窖内沙藏湿度控制在６０％左右，沙藏湿度控制在２～７℃，春季按常规扦插育苗进行，河北杨成活率最高可达９５．６％，平均成活率８９．３％；毛白杨成活率最高可达９６．４％，平均成活率９２．３％。     

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.     

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。     

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.