以电导法配合Logistic方程确定不同冬青抗寒性

采用人工模拟低温处理技术测定了6种(含品种)冬青树种离体叶片的相对电导率,并用Logistic方程计算它们的半致死温度(LT50)。结果表明:6种(含品种)冬青耐低温能力有显著差异,由高到低依次为克恩氏冬青>欧洲冬青>大别山冬青>‘蓝少年’冬青>杂种冬青>‘蓝少女’冬青,其半致死温度值LT50在-11～-24℃之间。     

DA-6对不同品种北美冬青生长和生理特性的影响

以北美冬青'冬红'冬黄'格瑞'和'奥斯特'4个品种营养钵苗为试验材料,通过施用不同质量浓度(20,30,50 mg/L)的DA-6,研究其对北美冬青株高、冠幅、单株生物量、光合及可溶性糖等的影响.结果表明:30 mg/L DA-6处理下,'奥斯特单株'格瑞'的生长最好;20 mg/L DA-6处理下,'冬黄'冬红'生长最好.各品种株高、冠幅、单枝长及生物量最大,其中'奥斯特'单株鲜质量和干质量分别达到68.84,31.90 g.不同质量浓度的DA-6处理,各品种净光合速率、气孔导度、蒸腾速率与对照相比,均呈现出不同程度的增加,其中20 mg/L处理,'冬红'净光合速率最大,达到8.44μmol CO2/(m2.s).一定质量浓度的DA-6可促进北美冬青叶片可溶性糖积累,其中30 mg/L处理'冬红'格瑞',可溶性糖达到最大值,分别比对照增加了52.34％,36.09％.     

戴云山自然保护区冬青属野生植物资源调查与分析

文章采用标准样地方法调查戴云山保护区内冬青属野生植物资源,并观测其花期、花色、果期、果色、叶质、叶型特征。结果表明,该区冬青属野生植物共有15种,且具有较突出的观赏价值。花期3~7月,花朵较小,花色丰富;果期7~12月,果色以红色为主;叶以薄革质或厚革质为主。在本次调查所有样地出现野生冬青属植物频次最大的是钝齿冬青、梅叶冬青,最小的是尾叶冬青、黄毛冬青;大部分冬青属植物均分布在1 000~1 400 m海拔,钝齿冬青的海拔分布范围为最广;区内冬青属植物主要分布于黄山松阔叶混交林,在黄山松纯林、马尾松纯林和灌木林分布较少,且均为群落伴生种,重要值较低。     

柃木等5种地被植物的抗旱性研究

将柃木(Eurya japonica)、滨柃(E.emarginata)、厚叶石斑木(Raphiolepis umbellata)、赤楠(Syzygium buxifolium)、钝齿冬青(Ilex crenata)5种地被植物进行干旱胁迫处理,观察记录不同植物的外部形态、植株死亡等症状以及不同植物组织的含水率变化,并通过隶属函数的方法进行综合评价,结果表明:同等条件下,5树种抗旱性强弱依次排序为赤楠＞滨柃＞厚叶石斑木＞钝齿冬青＞柃木.     

呼吁保护和发展酸黄柏

在伊克昭盟准格尔旗分布着一种保持水土效果很高的好树种——酸黄柏。酸黄柏属小檗科。名叫鄂尔多斯小檗,是一种落叶灌木,树高1～2米,叶倒卵形或倒披针形,全缘或有齿,在刺掖两侧常成簇对生,每簇3～5个叶片,叶长3厘米左右,叶背白色。枝条灰褐色,细瘦枝条有棱。短枝基部外侧常有刺。花黄色。果实为长圆形浆果,9月成熟,鮮红色,每粒果实含有1～2粒种子。木料深黄色。在准格尔旗,酸黄柏分布在石质山区的山坡、荒沟及崖头。这些地方其他树种很难生长,而酸黄柏生长很好。笔者见到     

优良灌木沙棘林的营造技术

沙棘(Hippophae rhamnides L.)也叫酸刺(陕西)、醋柳(山西)、黑刺(青海)，是一种具有固氮能力的胡颓子科沙棘属野生落叶灌木，耐于旱、耐瘠薄，防风固沙，生态适应面宽。多年来沙棘主要作为营造水土保持林和薪炭林树种被广泛栽植，但随着营养价值和药用价值的综合开发，沙棘已成为一种集社会、生态与经济效益于一身的珍贵树种。     

三种紫胶虫寄主在海南岛的栽培技术

滇刺枣(Ziziphus mauritiana),苏门答腊金合欢(Acacia glauca),大叶千斤拔(Moghania macrophylla)是紫胶虫的优良寄主树。滇刺枣为小乔木,果实可作水果食用,果仁可入中药;苏门答腊金合欢和大叶千斤拔是灌木,既可生产紫胶,同时也可作为薪炭材。这三种树木适生性强,耐干旱贫瘠,生长较快。1984年初我们从云南引进了这三种树种在坝王岭乌烈林场和琼海上蛹区林场进行栽培试验,现将结果整理如下。一、育苗     

几种常绿树种的介绍

在我国西部地区植树种草的热潮中，所用树种方面存在着落叶树种多，而常绿树种少的现象，这在一定程度上影响了绿化的效果，尤其冬春季节更加明显。现介绍几种适合于我国西部地区生长的耐旱、耐寒、耐风沙的常绿树种。一、沙冬青豆科沙冬青属，常绿阔叶灌木。叶多掌状3复叶，小叶菱状椭圆形，长2厘米～4厘米，宽0.6厘米～2厘米，总状花序顶生，花黄色，结荚果。产于内蒙古、新疆、陕西、甘肃、宁夏等省区。喜光、耐旱、耐寒、怕水湿。多生长于荒漠沙地，为绿化沙丘的优良树种。播种繁殖，不宜移植。移植树忌浇水，可用容器育苗克服移植难的…     

7个常见绿化树种的抗逆性研究

通过对花曲柳、黄栌、火炬树、山杏、复叶槭、卫矛、五角枫等7个树种进行不同程度的水分胁迫处理和遮阴胁迫处理，进行相关生理指标测定，初步探讨了这7个树种的耐旱性及耐阴性特点，结果表明：五角枫、花曲柳、复叶槭的抗脱水能力较强，是较为耐旱的树种；卫矛、花曲柳、复叶槭和火炬树表现出很好的耐阴性，黄栌和五角枫的耐阴性较差，山杏具有一定的耐阴性，但遮阴强度不宜过大。     

香樟新品种'涌金'

'涌金'系香樟种子变异种,叶、花呈金黄色;初生新枝为嫩黄色,半木质化后为浅红色,后转鲜红色;幼果果皮呈淡黄色,果柄果梗呈黄色.由于该品种叶、花艳丽,枝干夺目,并有季相的色彩变化,具有较高的观赏价值与园林应用前景,适宜作园林景观树、庭院树、行道树和四旁树种.     

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.     

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。