锥栗无性系产量变异及选择的研究

通过选优，进行无性系测定表明，锥栗优树于性系在产量性状上有着极显著的差异，高产无性系是最低无性系产量的２倍，超过平均产量的５７．０３％，每年平均单株产量达５．９２ｋｇ，每亩产量可达２３６．８ｋｇ，根据生产力指数，将参试的１６个无性系分为４类，其中高产的无性系２个，遗传增益达４５．２０％，较高产无性系３个，平均遗传增益２３．５４％。     

杉木速生优良无性系选育

在杉木优良种源的基础上,选育出一批杉木速生优良无性系。通过13 a的研究表明,各无性系间胸径、树高、单株材积差异极显著,且具有较大的广义遗传力。根据杉木无性系培育目标,选育出18个杉木速生优良无性系,入选12 a生无性系的平均树高、胸径和单株材积分别为11．03 m、16．98 cm和0．135 6 m3,与对照相比,树高、胸径和单株材积的遗传增益依次为10．71％、37.97％和113．08％;现实增益分别为14．25％、47．61％和140．01％。     

毛白杨多功能新品种选育研究

观测北京、河北、河南３地点的１３年生毛白杨无性系试验林,无性系间的树高、胸径、木材密度、纤维长度等性状的差异均极显著;无性系的遗传稳定性、生长适应性、主干通直系数、树体形态系数、抗病虫指数等性状存在一定差别。材积生长量无性系×地点交互作用极显著,无性系间生长型不同（“广适型”、“高产型”、“低产型”）。无性系的材积生长量、木材密度、主干通直系数、树体系数和抗病虫害指数的重复率分别为０．５８０、０．５３６、０．３９０、０．４１１和０．５００,性状经济权重分别为０．３５、０．２５、０．１０、０．１０和０．２０,建立多功能型无性系的选择指数,其综合育种增益比对照品种≥１５％为中选优良无性系新品种。为北京、河北、河南分别选育出８个、７个和６个优良无性系,平均综合增益分别提高２３．９％、２４．９％和２１．０％;３个地点都中选的３７、３５１、９８３２和１０１２等优良无性系的平均综合育种增益提高２５．１％。所选无性系皆为雄性,显著提高了城乡绿化效应。     

杉木优良无性系早期选择

对广东省于１９９３－１９９４年营造的１２块杉木无性系测定林的３－４年生材料进行分析,结果显示：有２／３以上的试验林的生长性状方差分析结果达到较显著差异水平以上,最优无性系的树高为最劣无性系的１．６４倍－３．３３倍,表明这些试验林中的无性系间存在着显著的遗传差异,且优、劣无性系间生长差异极为悬殊;经综合评选,从１１３１个参试无性系中,初步筛选出１０３个优良无性系,其平均树高增益达１３．９８％,其中Ｇ     

杉木无性系的遗传变异及优良无性系选择

试验揭示了杉木无性系在树高、胸径、单株材积和开花结果等方面有巨大的遗传差异。从99个参试无性系中选出了6个优良无性系，与种子园实生苗相比较，树高增益19％－26％，胸径增益17％－34％，单株材积增益50％－114％。分析了杉木家系选择和无性系选择的遗传改良潜力。无性系树高、胸径和单株材积的遗传变异系数分别是家系遗传变异系数的2．6倍、3．1倍和3．1倍。在入选率相同的条件下，无性系树高、胸径和单株材积的选择响应分别是家系选择响应的2．8倍、3．6倍和3．5倍。     

锥栗数量性状遗传参数分析

锥栗７年无性系测定和遗传参数分析表明：锥栗坚果产量的遗传方差分量为１６．００％～５２．６６％，平均３６．４６％；无性系重复力Ｒｃ为０．６０３９～０．８９６７，分株重复力Ｒｒ为０．１６００～０．５２０５。多年度无性系产量的基因型主效应占３１．９４％，年份效应占１２．７３％，基因型×环境（年份）ＧＥ工作效应不显著。树高、胸径、冠幅、平均枝长和单叶面积等生长性状的遗传方差分量Ｖｇ为５２．３９％～６６．３４％；Ｒｃ为０．９１６７～０．９８４９。Ｒｒ为０．５２３９～０．６６３４。产量的遗传增益△Ｇ为５０．５５％～７８．２５％，平均５９．７８％。选择锥栗优良无性系可以取得明显的效果。     

尾叶桉无性系生长比较研究

对12个尾叶桉无性系的生长性状差异分析和比较结果表明：各性状在无性系间差异均极显著，各性状的无性系重复力75．24％～94．32％，单株重复力为43．18％～80．57％。冠幅的重复力最小，材积最大。5．5年生时共有4个无性系生长量超过总体家系平均值，生长最优的无性系平均单株材积达0．1684m^3，是最差无性系的253．78％，是平均值的58．38％，比最优对照U6无性系高79．33％。应用主成分分类方法，将无性系分成6类。速生型无性系较慢生型无性系的树高、胸径和材积分别高出30．40％、57、74％和221．64％，增产效果十分显著。     

杉木无性系幼树高生长的遗传变异

杉木８２个无性系间１－４年生树高差异极显著，生长量最大相差达１．６－２．７倍。遗传变异系１２．５－２２．８％，广义遗传力估值０．６３３－０．９４１，遗传变异幅度和遗传控制程度都有随树龄增大而变小的趋向。按１０％的入选率，中选无性系的树高平衡遗传增益可达２５％左右，但无性系相对于种子园子代的树高生长优势可能因树龄小而尚水表达出来，２年生与３进行了分析和讨论，认为以提高木材产量为目标选择优良无性系的工     

杂种落叶松无性系评价

16年生无性系测定林方差分析结果表明，早期子代测定林中家系的优、中、劣单株并不能完全决定其无性系的后期表现；优良家系中选择出的优良单株(无性系)经过无性系评价。筛选出的优良无性系居多。但家系问树高差异显著、胸径差异不显著；无性系问树高差异显著、胸径差异不显著；8805组入选的12个无性系树高均值大于组内均值的12．5％。8806组入选的7个无性系树高均值大于组内均值的13．5％。     

杉木无性系生长性状的遗传变异及优良无性系早期选择

经对5年生杉木无性系试验林中36个无性系的树高、胸径、材积3个性状进行分析,结果表明:各性状无性系间差异极显著,且有较高的重复力和中等变异系数;生长性状间有较密切的遗传相关关系,以生长性状为基础,初选出6个较速生的无性系,其平均材积对照比较,现实增益为92.08％,遗传增益为71.34％。     

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。