桃金娘种子育苗技术研究

对桃金娘种子育苗技术进行研究,掌握桃金娘种子育苗处理方法及袋苗管理技术要点,为华南地区进一步开发桃金娘提供科学依据。试验结果表明:桃金娘种子播种前用60℃清水浸泡24h的平均发芽率最高,为92.30%;出芽快且整齐。     

不同处理对神黄豆种子发芽的影响

用剪刀剪、锉子锉、与瓜子石混搓等机械处理法以及用5%氢氧化钾、98%浓硫酸等化学处理法对神黄豆种子进行预处理,3倍种子体积沸水浸泡并自然冷却浸种48 h,观察并统计种子吸胀粒数、种皮破裂数后置床进行发芽测定。结果表明,除与瓜子石混搓处理外,其余处理均能促进种子吸水膨胀,显著提高神黄豆种子发芽率。其中以98%浓硫酸浸泡2 h处理效果最好,其吸胀率达98.0%、发芽率最高,达88.3%,吸胀破皮率、不正常发芽率均为0%;其次是锉子锉处理效果好,其吸胀率达99.0%,发芽率可达84.7%,吸胀破皮率、不正常发芽率均为0%;用5%氢氧化钾进行浸泡处理,对种子发芽有一定的促进作用,但发芽不整齐,发芽速度慢,处理14 d吸胀率为59.7%、发芽率最高为48.0%;与瓜子石混搓处理效果相对较差,对神黄豆种子发芽的促进作用不明显,吸胀率为5.0%、发芽率为5.0%。     

不同处理对格木种子发芽的影响

格木种子催芽试验表明:擦破种皮可有效地促进格木种子的发芽,发芽率比对照高42 5%;100℃热水浸种和浓硫酸拌种30min的处理方法对种子发芽提高有明显的促进作用,发芽率分别比对照高71 25%、73 75%,发芽势分别比对照高58 75%、63 75%,平均发芽速都比对照提前6d。     

油松种子“引动”处理对发芽效果的影响

试验测定了不同化学药物、浓度、浸泡时间和单纯用水浸泡渗透处理对油松种子发芽的影响。结果表明,阿司匹林、赤霉素、聚乙二醇对油松种子发芽有显著的促进作用,经过3种药物处理的种子在室温11~14℃的情况下,第6天或第7天开始发芽,对照第9天发芽;发芽势（第10天的发芽率）经过处理的在22%以上,高者可达31%,而对照仅为8.3%。单用自来水做渗透引动处理也能提高油松种子的发芽势和发芽率。     

不同温度对刺榆种子发芽特性的影响

在实验室条件下对刺榆种子进行发芽试验的结果表明:刺榆种子在10~35℃均能发芽,最佳发芽温度为25℃,发芽率达90%以上,种子的发芽活力最强。不同温度处理对刺榆种子发芽特性的影响均差异显著,温度的升高能明显缩短种子的发芽时间,发芽率、发芽势、发芽指数、活力指数随温度升高而升高,达到最佳发芽温度后,随温度增加而降低。不同温度处理对种子发芽率的影响排序为25℃20℃与30℃35℃15℃10℃。10℃、15℃、20℃、30℃和35℃条件下种子的发芽活力较最佳温度条件分别下降92%、67%、33%、34%和57%。     

保水复合肥对草木樨发芽率及促进生长试验研究

采用不同保水复合肥对草木樨的发芽率及促进生长的试验研究表明 :保水复合肥 1～ 4号对种子发芽及幼苗生长有促进作用。 1号、2号对种子发芽效果表现最佳 ,但 1号、2号对促进生长没有 3号、4号显著。 3、4号比 CK4的苗高分别增高 4 1 .1 6%、35 .97% ,比 CK4的发芽率分别提高 4 5 .5 7%、4 7.72 %。由此可知 ,3、4号对提高发芽率及促进生长都有显著作用。     

截杆处理对大龄杉木种子园种子产量与品质的影响研究

以杉木种子园大龄母树为研究对象,对其进行截杆试验,对比分析截杆与未截杆处理对母树球果产量、球果大小、种子产量、种子质量以及种子发芽能力的影响。结果表明,截杆处理对大部分无性系母树种子产量、种子质量以及种子发芽能力均具有显著的促进作用。截杆处理对球果产量指标影响不显著,但截杆后球果鲜重和干重的综合增益值均在60%以上;单株种子重、出籽率、种子千粒重和优良度的综合增益值分别为104.23%、33.90%、17.08%和82.72%;种子发芽率、发芽势和发芽指数的综合增益值分别为130.32%、134.41%、133.28%。说明截杆处理可提高母树种子产量和质量,且可显著提升种子的发芽能力,提高种子发芽率和整齐度,缩短种子发芽时间。     

温度和光照对多花黄精种子萌发的影响

为了解多花黄精种子的萌发特性,探索其种子萌发的最适宜条件,以年珠林场收集的多花黄精种子为研究材料,开展其种子形态测定以及温度和光照对其种子萌发特性影响的研究。结果表明：温度对多花黄精种子发芽率、发芽势、发芽指数和平均发芽时间的影响达到显著水平;在10℃～35℃范围内,随着温度的升高,种子的发芽率、发芽势和发芽指数均呈现先增加后减小的趋势,而平均发芽时间则呈现先减小后增加的趋势;当温度为25℃时,种子发芽率、发芽势和发芽指数最高,分别为93.4%、70.1%和48.5,平均发芽时间最低为11.4 d。光照对多花黄精种子发芽率、发芽势、发芽指数和平均发芽时间的影响不显著。试验结果为多花黄精栽培育苗提供技术支持和理论支撑。     

半红树植物水黄皮发芽试验

对水黄皮(Pongamia pinnata)种子去皮沙播、未去皮沙播、去皮泥沙播、未去皮泥沙播四种处理的发芽情况及水黄皮种子发芽临界含水率进行研究。结果表明:去皮有利于显著提高水黄皮种子发芽率和发芽势;去皮泥沙播的发芽率和发芽势均为最优,是宜采用的生产方法;水黄皮种子发芽临界含水率测定表明,种子含水率为14.05%～47.19%时,适宜发芽,发芽率为83.33%～96.67%,含水率为6.97%～11.69%时,发芽率显著下降,为13.33%,低于4.61%时,则停止发芽。     

天然油菜素内酯对臭椿种子发芽及下胚轴切段伸长的影响

采用种子发芽力和下胚轴切段伸长测定的方法,研究了天然油菜素内酯对臭椿种子发芽和下胚轴切段伸长的影响,结果表明,不同浓度的天然油菜素内酯处理对臭椿种子的发芽率、发芽势、平均发芽速度均由明显的促进作用。与对照相比,0.3 mg/L浓度的天然油菜素内酯处理使臭椿种子发芽率提高了33.3%,发芽势提高了9.4%,发芽时间缩短了37.7%;0.4 mg/L浓度的天然油菜素内酯处理使臭椿下胚轴切段伸长比对照提高了29.4%。     

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.