珍稀濒危树种银缕梅种子萌发特性研究

在测定银缕梅(Parrotia subaequalis)种子形态和千粒重的同时,研究了不同储藏方式、温度、赤霉素处理、光照条件对种子萌发的影响.结果表明:银缕梅种子呈长纺锤形,平均长径8.08 mm,平均短径3.79 mm,千粒重46.35 g；储藏方式对银缕梅种子的萌发影响较大,其次为温度,赤霉素浓度对种子发芽率的影响较小,种子萌发的最佳处理组合为常温沙藏、赤霉素浓度600 mg/L、温度20～25℃,发芽率达73.73％；适度光照可缩短种子发芽时间,提高发芽势.     

耐热性白桦种子筛选研究

为筛选适应北京地区气候的耐热白桦种源,丰富北京园林绿化植物种类,本试验对收集的5个不同种源白桦种子做发芽率试验,得出以下结论:(1)不同种源种子的发芽率、发芽势、千粒重等指标,是研究不同种源种子之间的差异性的定性指标。(2)东北4个种源的种子千粒重、发芽率、发芽势均表现良好,KYY种源最差,但种子耐高温能力最强。(3)白桦自交,种子千粒重、种子活力(发芽率、发芽势)明显低于杂交组合。(4)白桦生殖生长受气候环境影响较大,气温高种子质量差。     

不同种源麻疯树种子品质及苗期生长研究

通过对6个不同种源麻疯树(Jatropha curcas)进行种子观测及播种育苗试验,对种子品质、苗期生长做比较分析,结果表明:不同种源间种源间千粒重、发芽率、发芽势、R值差异较大,变异系数较高,形状差异不明显;苗高、地径分别存在显著和极显著差异;生物量差异明显,但不均衡。经过综合评价,初步选出贵州贞丰和百色隆林2个种源为苗期优良种源。     

东革阿里种子生物学特性研究

为研究药用植物东革阿里(Eurycoma longifolia)种子的生物学特性,通过形态学观察、种子发芽试验等方法对5个东革阿里种源的种子形态、千粒重、种子含水量、种子发芽率等指标进行测定.结果表明:5个东革阿里种源的种子外观形态差异不大,其千粒重和含水量从大到小排列均为:海岸带种源＞海岛种源＞低地种源＞大陆种源＞山地种源.5个种源中以海岸带种源发芽率最高,为52％;低地种源和海岛种源发芽率低,仅为28％和34％.初步筛选出海岸带种源东革阿里种子可作为优良种质资源.     

竹子种子品质测定和发芽率试验

对不同时间采集的12个种源地竹子种子进行随机抽样,得到12个样品,利用恒温发芽箱进行发芽率实验及种子品质测定.结果表明,种子的纯净度、千粒重、发芽率、发芽势分别为32.4％ ～ 96.7％、11.5 ～107.5 g、0％～72％、0％ ～ 44.5％.多数种子发芽率为10％ ～50％,巨竹种子发芽率较高,可达50％以上.种源不同,种子保存条件不同,种子发芽情况也不同.     

两种不同种源麻疯树种子发芽特征探讨

比较分析两种不同麻疯树种源种子发芽率、发芽势、发芽速度、发芽指数、发芽条件以及外观品质,结果表明：种源、种壳、种质、湿度、氧气以及种子前处理影响了种子发芽率、发芽势、发芽速度、发芽指数;破壳比未破壳的发芽效果好,种源A比种源B种子发芽率高,发芽期间应保持一定的湿度和通气条件,前期的消毒、浸种也是必需的环节。     

不同种源苦楝种子形态特征和播种品质差异研究

本研究以苦楝自然分布区内8个种源的种子为研究对象,对种子形态特征和播种品质等生物学特性进行了测定,结果如下：（1）苦楝种子大小存在显著的产地差异,不同种源苦楝种子纵径、横径、纵横径比及千粒重差异均达0．01极显著水平。（2）不同种源苦楝种子发芽率均较高,变幅为50％～81％,平均发芽率为65％,变异系数为15％;发芽指数变化幅度为1．531—2．919,变异系数为19．45％;活力指数变幅为0．054～0．330,变异系数达56．64％。（3）综合种子形态指标和播种品质指标可以分析得出福建平潭,陕西杨凌、广西武鸣、安徽歙县等种源种子品质较好,湖北黄冈种源种子品质较差。     

木荚红豆育苗技术研究

采用随机区组设计木荚红豆种子不同采收期、播种方式、播种期、种子处理、种源对比研究。结果表明:不同采收期木荚红豆种子产量和质量存在差异,本地区种子采收期以11月以后为好;播种方式对苗木质量和产量无明显差异,但条播节省种子,便于锄草、施肥;播种期对苗木质量和产量存在差异,以3月后为好;种子处理对种子的发芽率、成活率无明显差异,但经机械处理种皮的种子出苗早且整齐;不同种源对单株生物量有所差异,但不影响苗木质量。     

不同种源八月瓜种子发芽率及总黄酮含量测定研究

为了在海南推广种植八月瓜,试验通过收集不同种源的八月瓜,并开展种子发芽率试验和总黄酮含量的测定。结果表明:种子在播种前采用10%赤霉素浸泡种子2h,随后采用撒播的方式进行播种,育苗基质为全河沙基质时发芽率最高,达到92.6%;不同种源的八月瓜果肉中总黄酮含量最高的是云南种源(1.173%),其次为广东种源(0.789%)和贵州种源(0.738%);果皮中总黄酮含量最高的是湖南种源(1.412%),其次为贵州种源(0.818%)和广东、江西种源(均为0.782%);总含量的排序为:湖南种源云南种源广东种源贵州种源江西种源。     

湖南省主要经济林树种(品种)种子等级标准的研究

由申南林学院和湖南省林业厅共同研究完成的《湖南省主要经济林树种（品种）种子等级标准的研究》1993年12月通过由省林业厅组织的鉴是。专家认为，该项研究居国内同类研究领先水平。该成果对我省范围内的11个主要经济林树种种子的收购、贮藏和播种实践有一定的指导意义。研究人间建议种子分级指标为：①杜仲：一级种子发芽率为80％，净度为98％；二级种子发芽率为65％，净度98％；三级种子发芽率50％，净度96％。含水量为30％－55％。②葡萄桐：一级种子发芽车95％，净度98％．二级林子发芽率85％，净度98％，三级种子发芽率65％，净度96％…     

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.