松突圆蚧的生物防治

松突圆蚧是严重危害马尾松林的检疫对象,2003年由广东传入广西,2005年起广西边界林区松林开始枯萎,灾情明显出现。为寻找防治途径,2006年～2008年,广西北流市连续3年从广东引进“本地小蜂”开始实施对松突圆蚧防治作业,2007年起开展生防菌菌液防治松突圆蚧试验,2008年利用生防菌菌粉防治松突圆蚧。     

松突圆蚧生防菌在马尾松不同林型中的扩散效果

为探讨松突圆蚧生防菌粉的扩散规律,从染病的松突圆蚧蚧虫体上分离获得15株虫生真菌,经毒力试验后筛选出2个毒力较强的菌株(1号菌广布拟盘多毛孢Pestalotiopsis disseminata (Thuem.)Stey,2号菌橄榄色拟盘多毛孢P.olivacea (Guba) G.C.Zhao & He Jie),设计了松突圆蚧生防菌1,2,3号(1号与2号混合)3种粉剂,分别在博白林场和岑溪集体林区的不同马尾松林型中进行了菌粉的扩散试验.结果表明:3种生防菌都有明显的扩散效果,对松突圆蚧都可起到较好的防治作用;松突圆蚧生防菌粉剂在马尾松不同林型的林间扩散效果有明显差别,在人工纯林中的布菌点距离可达70 m,而在林分结构复杂的飞播林中的布菌点的距离应小于50 m.根据试验初步推测,生防菌的自然扩散距离为40～60 m,可控比例为1:3.     

松突圆蚧生防菌的毒力试验

将广西大学林学院提供的菌株喷施于被松突圆蚧侵染的松树树冠上,结果表明:5种生防菌对松突圆蚧的致死率均远远高于松突圆蚧的自然死亡率,防治效果显著。第1次试验进行后的第125天和第2次试验进行后的第85天再次对松突圆蚧的死亡率进行统计,结果表明菌液对松突圆蚧的防治作用可以持续4个月左右。     

松突圆蚧本土寄生蜂的研究

我国利用松突圆蚧(Hemiberlesia pitysophila)寄生蜂已经20多年,但除了占比例很少的试验点外,均未达到控制松突圆蚧成灾、扩散、蔓延、恢复林木长势的目的.为了系统的了解松突圆蚧寄生蜂的应用情况,本文对本土寄生蜂防治松突圆蚧的研究成果进行了归纳和总结,以期全面的认识本土寄生蜂防治松突圆蚧的实际情况.     

广东省松突圆蚧发生区划研究

依照松突圆蚧Hemiberlesia pitysophila Takagi的灾害特点,将广东省松突圆蚧发生区以县级为单位进行了发生区划,并构建了基于气象因子的灾害程度判别模型,依据该模型结合林分构成和林业经营特点研究了松突圆蚧发生区划,将广东省松突圆蚧发生区划分为轻度分布、中度发生和重度危害3个区域,并提出了各区域松突圆蚧防治策略.     

寄生蜂花角蚜小蜂防治松突圆蚧的研究

花角蚜小蜂(Coccobius azumai)属蚜小蜂,是日本松突圆蚧上的优势种天敌.有关资料表明[1],在松突圆蚧原发生地日本冲绳,由于花角蚜小蜂的寄生控制,松突圆蚧对松树危害并不严重.因此,1986年我国从日本首次引入了花角蚜小蜂,并进行了大量的研究与应用试验.本文综述了自1999年以来的寄生蜂花角蚜小蜂防治松突圆蚧(Hemiberlesia pitysophila)的研究,以便更系统了解寄生蜂防治松突圆蚧的情况.     

松突圆蚧花角蚜小蜂人工收蜂技术研究与应用

松突圆蚧花角蚜小蜂Coccobius azumai Tachikawa是有效防治松突圆蚧Hemiberlesia pitysophila Takagi的重要寄生性天敌.在前人对花角蚜小蜂研究的基础上,2002年5月从日本冲绳引进松突圆蚧花角蚜小蜂后,改进了人工大量收蜂技术,应用自行设计的收蜂棚进行敞口式大量收蜂,大大提高了收蜂量.2006-2007年分别收到花角蚜小蜂22 372头和54 556头.在福建松突圆蚧发生区推广应用,为松突圆蚧的生物防治提供了行之有效的持续控制措施.     

广东松突圆蚧发生类型区分析及防控对策

松突圆蚧是一种危害松林的外来有害生物.为寻求以生物防治为主的综合治理措施,分析了广东松突圆蚧发生类型区,分别介绍了松突圆蚧低虫口分布区、不稳定区、严重危害区3种发生类型区的分析情况,同时提出发挥本地寄生天敌对松突圆蚧的防控作用,并进一步探讨利用花角蚜小蜂的有效途径等综合治理对策.     

浙江省松突圆蚧入侵风险分析

根据松突圆蚧的生物学特性、分布状况、潜在风险性和奇主经济重要性等,对浙江省松突圆蚧入侵风险进行了分析评估,结果表明,浙江省为松突圆蚧生态适生区和易爆发流行区,松突圆蚧入侵风险值达2.092 4,为高度危险的外来林业有害生物,并提出了加强检疫和进行松林林相改造的营林措施来有效减少入侵风险.     

寄生蜂防治松突圆蚧的研究进展

文章介绍了松突圆蚧（Hem iberlesia pitysophilaTakagi）的发生历史、危害及防治现状。从生物防治上分别介绍了松突圆蚧寄生蜂花角蚜小蜂（引进种）的生活习性、对松突圆蚧的控制效能、近年来广东花角蚜小蜂种群数量下降的原因等研究进展,以及应用本地寄生蜂防治松突圆蚧的进展情况,并从林间生态位的角度介绍了松突圆蚧及其3种寄生蜂的相互关系。最后讨论了应用寄生蜂防治松突圆蚧过程中存在的问题,提出了相关建议。     

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.     

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。     

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.