麻竹无性系选育的研究

本文报道了对麻竹实生苗生长状况和实生苗无性系选育方法。通过人工授粉获得麻竹种子，用圃地培植及无菌播种组培两种方法培育麻竹实生苗无性系，结果表明：（1）收集优良开花母株，利用人工授粉方法取得麻竹种子，可为优良无性系的选育培育较为优良的实生苗群体，有利于提高选育的有效性；（2）圃地培植的实生苗无性系在16个月龄和28个月龄时的生长显著相关，16个月龄时进行较大强度的无性系筛选，可靠性较大；（3）提早分株种植能加快实生苗无性系的总体生长与繁殖，利于加快无性系选育的进程；（4）无菌播种组培条件下，组培中无性系的生长特性与其移栽圃地后的生长特性十分相关，各无性系固有的生长特性在培养3-6个月期间逐渐表现，可在此时进行离体早期选择。     

麻竹实生苗无性系选育的研究

报道了对麻竹实生苗状况和实生苗无性系选育方法的研究.通过人工授粉获得麻竹种子,用圃地培植及无菌播种组培2种方法培育麻竹实生苗无性系,结果表明(1)收集优良开花母株,利用人工授粉方法取得麻竹种子,可为优良无性系的选育培育较为优良的实生苗群体,有利于提高选育的有效性;(2)圃地培植的实生苗无性系在16个月龄和28个月龄时的生长显著相关,16个月龄时进行较大强度的无性系筛选,可靠性较大;(3)提早分株种植能加快实生苗无性系的总体生长与繁殖,利于加快无性系选育的进程;(4)无菌播种组培条件下,组培中无性系的生长特性与其移栽圃地后的生长特性十分相关,各无性系固有的生长特性在培养的3～6个月间逐渐表现,可在此时进行离体早期选择.     

麻竹实生苗群体中无性系选育的研究

报道对麻竹实生苗生长状况和实生苗无性系选育方法的研究。通过人工授粉获得麻千篇一律中子，用辅地培植及无菌播种组培两种方法培育麻竹实生菌无性系，结果表明：收集优良开花母株，利用人工授粉方法取得麻竹种子。可为优良无性系的选育培育较为优良的实生苗群体，有利于提高选育的有效性。     

巨龙竹幼年竹优良无性系早期选育研究

通过对巨龙竹实生苗生长性状的观测,总结出了20个月苗龄时,对其种胚组培苗进行优良无性系选育是相对可靠的,筛选出了8个各种性状均较优的无性系。并对各无性系在试管微环境下和圃地的生长表现进行对比,归纳了二者之间的相关性,为巨龙竹幼年竹组培在试管内的早期选优提供试验依据。     

影响长白松无性系搜集圃初期球果,种子产量因子的探讨

１４年生长白松无性系搜集圃的球果、种子产量较低。本文从不同长白松无性系，以及其开花物候期、无性系内植株生长优劣和进行人工授粉四个方面对其球困种子产量进行探讨后，提出了选择优良无性系，培育整齐二菌，进行集约经营和进行人工辅助授粉等三项营建优质优势高产长白松无性系种子园的具体措施。     

油橄榄造林途径的探讨

本文提出以20世纪60年代引种驯化的油橄榄作母本,通过人工授粉产生杂交子代,从子代中选育抗病苗木,培育优良无性系用于造林。造林途径主要是培育抗病实生苗嫁接优良无性系用于造林;从杂交子代中选育抗病高产优株,通过无性系快速繁殖技术育苗造林。     

麻竹实生苗无性系的组培繁殖及其生长

对采用人工辅助授粉所得的麻竹种子,经无菌发芽增殖培养而成的实生苗无性系进行组织培养繁殖试验及生长观察。结果表明,同一培养基中的各无性系之间增殖、生长状况各不相同,在芽萌发后的培养过程中,一部分无性系逐渐褐化死亡,一部分无性系生长状况不断得到改善。经３个月的培养,各无性系的基本生长特性能得到体现,３个月后增殖速度较快、生长健壮的无性系,在以后的增殖培养过程中能保持较好的生长状态。按其在培养中的生长状     

几个丛生竹开花授粉特性及麻竹苗期初步选择

对麻竹、绿竹、大头典、吊丝单、撑篙竹几个丛生竹种进行开花生物学特性观测和人工授粉;对麻竹进行苗期选择.结果表明:麻竹花雌雄蕊异时成熟,柱头和花粉发育良好,易于授粉;绿竹属3个竹种竹花雌蕊退化,花粉少或无,授粉困难;撑篙竹花雌雄蕊同时成熟.2002～2003年、2003～2004年分别收获麻竹种子388粒、麻竹种内和麻竹×绿竹种子1 495粒,育苗成苗率分别为32.5%,36.5%.19个月龄的麻竹实生苗平均每丛发笋量为8.89秆,平均竹高187.08 cm,平均地径1.66 cm;在竹高、地径方面占优势的群体发笋数量中等.     

杉木优良无性系组培繁育试验

通过对杉木优良无性系的组培繁育试验，筛选出一组广谱、高效的培养基和组培苗最佳移栽期及移栽后的培育管理方法；营造了组培苗与实生苗及各种源无性系不同繁殖方式的对比试验林，进一步研究其造林效果的差异。结果表明，组培苗造林在树高、地径等性状上均高于实生苗及常规无性繁殖苗。     

笋用竹良种选育的研究初报

为了培育优良的笋用竹,以提高竹笋的营养价值,改善其风味,进行了笋用竹良种选育研究.其方法是:引进优良的品种,并与本地的竹种杂交,从中选择其优良的无性系,结果表明:(1)麻竹与版纳甜龙竹、清甜竹杂交,已获得成功,其笋味不苦;(2)撑篙竹×麻竹7号,其竹笋的营养成分以及氨基酸总量和人体必须氨基酸的含量均高于其他种的竹笋,且产量高,加工性能好;(3)实生苗在试管内培养植株间生长差异大,其芽丛经生根诱导,生根率达60%;(4)人工促进萌发的次生枝扦插繁殖成活率达60%.并详细介绍了营建采萌圃的具体步骤.     

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。