光箨篌竹物候学的初步研究

采用固定样地竹株的观测和林分整体物候变化观测相结合的方法,分析了出笋成竹期、竹笋幼竹形成期、脱箨期、落(展)叶期、分枝期、梢部下垂期与单株、林分群体的关系以及气象因素对它们的影响,在建立光箨篌竹年物候谱基础上,将年生育划分为萌芽孕笋期、出笋成竹期、竹笋幼竹形成期和行鞭成芽期4个时期,并阐述了各时期的特点。     

光箨篌竹出笋成竹规律的研究

采用固定样地观测和随机样地调查相结合的方法,分析了光箨篌竹的出笋成竹规律以及不同径级竹笋和不同密度林分的出笋变化规律,进而分析了气象要素、立地条件和林分结构对出笋质量的影响,上述研究结果将为短周期工业用竹林的营建与培育提供依据。     

光箨篌竹竹笋幼竹生长规律的研究

对24株固定竹笋定时观测材料进行分析,表明了光箨篌竹竹笋幼竹的一些生长节律,阐述了出土期、生长级、林分密度和气象要素对竹笋成竹的影响,进而揭示了时进程类型与天气、气温和湿度的关系,探讨了它们在生产中的应用。     

苦竹出笋成竹规律的研究

对苦竹从出笋至成竹进行观察研究。结果表明：①出笋期可划分为初期、盛期、弱期和末期四个阶段。②竹杆高生长发育划分为四个时期，即生长初期、上升期、旺盛期和末期。③竹笋高生长停止后，竹杆开始抽枝、发叶、平均抽枝时间为19天，平均发叶时间为23天，竹笋从出土至成竹平均生长需98天。     

小佛肚竹抽枝长叶与竹叶凋落规律研究

通过对观赏竹种小佛肚竹抽枝长叶和竹叶凋落规律的观测研究,结果表明:8月中旬前出笋新竹当年完成抽枝,平均抽枝持续期25 d,以后出笋新竹至翌年4月下旬完成抽枝,抽枝持续期12~171 d。各出笋时期的新竹从竹笋出土至始抽枝的时间差异明显。8月下旬前、8月下旬~9月上旬、9月上旬后出笋新竹,抽枝持续期在时间阶段间差异显著,而时间阶段内差异不显著;8月中旬前出笋新竹当年完成长叶,其后出笋新竹至翌年5月上旬完成长叶,各时期出笋新竹长叶持续期无显著差异,平均12 d;抽枝长叶期23~182 d,总体呈迟出竹笋抽枝长叶期短的规律;不同季节间竹叶凋落量差异显著,以10~12月份最多,4~6月份最少,新叶抽发量以4~6月份最多。     

北京地区早园竹高生长规律及出笋长竹期的养护技术

本文以北京地区生长的早园竹（Phyllostachys propinqua）为研究对象,调查了早园竹的高度生长及竹林出笋规律。结果表明：竹笋的出笋时间不同,其成竹率也不同。出笋早的竹笋的成竹率较高;出笋越晚,竹笋的成竹率越低。据此可将早园竹的出笋期分为3个阶段：前期,中期,后期。3个阶段的时间大致相等,约为6-7d。前期笋的高生长期长、后期笋的高生长期短,它们高生长期的结束时间基本一致。早园竹的高生长遵循“慢一快一慢”规律,竹笋破土后14d和36d左右是高生长期的2个转折点,由此可将早园竹的高生长分为始期、盛期、末期3个阶段。早园竹的日最大高度生长量为51～75cm,占成竹平均高度的6．96％～9．04％。同时对早园竹出笋长竹期的养护技术进行了探讨。     

毛竹生长发育规律的调查分析

毛竹不同于其它树种,有其独特的生长发育规律。为了掌握毛竹地下部分——竹鞭、笋芽的生长发育规律和竹笋成竹规律,在湖南省湘阴县进行了长期的调查研究,结果发现影响毛竹产量和质量的关键因素是毛竹地下部分的生长发育条件:竹鞭在疏松、肥沃、湿润、板岩或页岩发育的黄红壤中生长最为适宜;竹鞭在土层中分布深、生长壮实,鞭芽饱满、生活力强、萌发力强、发笋多,竹笋粗壮、成竹率高,新竹胸径大、竹竿高、出材率高。     

淡竹林竹笋泉蝇生物学特性与防治研究初报

竹笋泉蝇(Pegomyia Kiangsuensis Fan)属双翅目花蝇科泉蝇属,主要为害竹笋,致使竹笋腐烂、发臭,不能成竹。竹笋因遭此为害,成竹率大为下降。淡竹林一般每年3代笋,2、3代笋受其为害,多不能成竹,竹笋的成竹率仅在50%左右,天长县淡竹林1563.2ha,分布在65000多户,竹林每公顷年收入6145.5元,最多可达15000元以上;据调查,竹笋泉蝇发生面积在     

黄甜竹生长发育规律初步研究

对黄甜竹生长发育规律进行了初步研究,结果表明:黄甜竹发笋期从4月中旬开始至5月上旬止,持续时间约25 d,出笋规律呈偏右正态分布。黄甜竹平均成竹率为61.36%,发笋前期和盛期成竹率相当。幼竹高生长历时45 d,高生长总量可达7～8 m。     

寿竹出笋及竹笋-幼竹高生长规律

通过对寿竹出笋和幼竹高生长阶段的调查,研究了寿竹笋期的生长发育规律。结果表明,寿竹出笋从5月初开始,出笋盛期为5月8日到5月21日,盛期出笋数量占84.7%,出笋全部持续时间约30天。寿竹的高生长持续60天左右,高生长符合Logistic模型。引起寿竹退笋的主要原因是虫害,占退笋的比例74.7%,造成退笋的主要害虫是竹笋泉蝇。该地区寿竹整个出笋期平均成竹率仅为11.7%。     

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.     

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.     

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。     

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.