邓恩桉等6种桉树的耐寒能力研究

通过对在江西北部试验地的温度记录及对6个桉树树种其9个品种的耐寒表现进行研究,发现了试验地的气温变化特点,并判断极限低温、不充分的耐寒锻炼是导致桉树寒害的主要原因;在-6.8℃低温中,本沁桉、溪谷桉的耐寒能力强,多利桉与邓恩桉具有一定的耐寒力,柳桉和巨桉不具有耐寒能力。选择出耐寒能力与速生性均优良的邓恩桉20748种源、本沁桉为推荐发展的品种。     

闽西北适栽桉树树种选择研究

自上个世纪90年代以来，闽西北进行了多批桉树树种引种或种源家系试验，结果表明：适宜闽西北地区推广种植的桉树有巨桉、邓恩桉、柳桉和赤桉，其中赤桉、邓恩桉最为耐寒。可以推广到闽西北大部份地区，巨桉、柳桉适宜闽西北较低海拔、绝对最低温度在-5℃以上的地区，但需要选择适宜的种源。树种内种源和家系间的生长性状、抗寒性存在显或极显差异，单株间的生长差异比家系间的生长差异大，而家系间又比种源间大。此外，桉树树种原产地的雨量分布情况对决定引种桉树极为重要。在高温潮湿的福建地区不适宜引进冬雨型桉树树种。     

广西耐寒桉树育种研究现状与对策

广西在耐寒桉树育种方面开展了引种试验、家系试验、优树选择以及杂交育种等工作 ,引进了邓恩桉(Eucalyptusdunnii)、赤桉 (E .camaldulensis)、溪谷桉 (E .badjensis)、蓝桉 (E .globulus )、巨桉 (E .grandis)、圆角桉 (E teleticornis)、史密斯桉 (E .smithii)、多枝桉 (E .viminalis)等一批树种及其种源 ,进行了有 10 4个邓恩桉家系参与的家系试验 ,选择出柳窿桉、邓恩桉等树种优株近 10株 ,成功培育出具明显杂种优势的柳窿桉(E .saligna×E .exserta)、尾赤桉 (E .urophylla×E .camaldulensis)、尾圆桉 (E .urophylla×E .teleticornis)等桉树杂交种 ,另外还开展了促进邓恩桉开花结实与邓恩桉组培繁殖的试验研究。建议加大耐寒桉研究力量 ,借鉴已有的国内外耐寒桉育种经验 ,引进更多耐寒桉优良基因资源以及加强对优良耐寒桉树种邓恩桉的开花结实与组培繁殖的研究攻关等     

广西耐寒桉树研究进展

广西耐寒桉树改良和栽培技术研究项目实施 3年来 ,着重开展了下面几个方面的工作 :(1)对 1991年建立的邓恩桉 (E dunnii)种源 /家系试验林进行了观测研究 ,包括种源及家系的生长表现 ,开花物侯与种子生产能力的研究 ,促进邓恩桉开花结实试验、邓恩木材基本密度的分析测定 ;(2 )从澳大利亚引进多枝桉、邓恩桉等 10多个耐寒桉树种 /种源 ,建立了新的耐寒桉品种试验林 ;(3)扩大邓恩桉栽培范围 ,在广西、江西以及湖南建立起邓恩桉种源试验与示范林 ;(4)开展了邓恩桉、柳窿桉 (E saligna×E exserta)组培无性繁殖研究 ,建立了 8个无性系无菌体系 ;(5 )对栽培耐寒桉树的柳州、桂林两地试验点的立地进行了评估。此外 ,还指出了项目存在问题及下一步的工作展望。     

广西桉树人工杂交育种研究

以广西东门桉树示范林项目的桉树杂交育种为代表的广西桉树人工杂交育种研究始于20世纪80年代,是在拥有大量遗传材料基础上的桉树改良,通过制订杂交育种策略,采取正确的杂交方法,培育出了一大批优良桉树杂交种,并进一步繁育筛选无性系,为广西及华南地区桉树造林提供了许多优良无性系,促进了广西及整个华南地区桉树人工林的快速发展,同时也吸引了投资商和国际公司到广西发展,促进了木材利用产业的发展。今后应加强纯种世代改良,进一步提高其遗传品质,以使杂交改良在亲本具有更高遗传水平上进行;另外,还应开展耐寒、观赏杂交改良方面的研究,这些方面应有较好前景。     

耐寒桉树丰产栽培试验初报

临武县自 80年代开始引种桉树 ,经过 10多年的栽培试验 ,赤桉耐寒能力最强 ,能耐 -8℃的低温。其次是巨桉。在优良立地条件和精心管护下可丰产。     

广西耐寒桉高产纤维材人工林

广西已建立的桉树人工林主要集中在较温暖的南部沿海地区。广西北部较冷凉的地区也有相对较小面积的桉树人工林,而且一些桉树种在该区域表现出较好的生产力。这些较冷凉地区的大部分林地都适宜进行耐寒桉树种选择研究。通过分析冷凉地区桉树人工林环境因子,结果显示,最适宜的耐寒桉为邓恩桉及柳桉的一些优良种源;在冷凉地区中较温暖的区域,巨桉(Eucalyptus grandis)的一些优良种源也是不错的选择。考虑一些树种的特性时,种植者和投资商除了注重其材积量外,更要关注它们的木材质量和纤维量。研究表明,与广西南部较炎热地区的多数桉树人工林里的桉树相比,邓恩桉(E·dunnii)具有更高的平均木材密度和纸浆量。因此,对于纸浆厂来说,邓恩桉木材将带给他们更高的效益。     

广西桂林耐寒桉树引种试验研究

本文概述了桂林1984年、1986年、1991年以来桉树引种概况。共引种22个树种(种源)现存20个。经过4—11年观察,能安全越冬、渡过-4℃低温、冰冻持续5天之久的恶夯天气。筛选出柳窿桉、邓恩桉、圆角桉、尾叶桉、巨桉等几个速生、适应性较强的树种,可在本地区适宜范围内引种推广,扩大栽培面积。邓恩桉可作为耐寒树种在桂北地区引种推广。     

桉树在合肥地区引种及抗寒性试验的初步研究

于2004年在合肥地区进行了4种桉树的引种驯化试验,分别于2005年和2008年对它们的各项生长指标、抗寒能力和引种成活率等适应性指标进行调查和分析。河红桉在合肥地区适应性强、叶色丰富、树形优美,并且综合其树高、地径生长量与成活率,表明河红桉在合肥地区有着很好的引种前景,初步筛选出河红桉为适宜合肥地区栽培的优良树种。     

巨桉种子园种子与普通种子造林对比试验初报

在福建永安国有林场开展了巨桉种子园种子与普通种子造林对比试验,结果表明:4年生时,巨桉种子园种子的林分生长量明显优于普通种子的林分生长量,其中以二代种子园种子的林分生长最快,一代种子园种子的林分次之;桉树种子园的种子造林增益明显,遗传改良成效显著;柳桉与巨桉普通种子造林的林分生长量相似。试验林遭遇-3.9℃寒流袭击仅受到轻微冻害,说明柳桉和巨桉具有较好的耐寒能力,在永安周边地区具有造林推广潜力。     

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.     

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.     

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.     

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.     

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。