靖远松叶蜂危害损失量研究

靖远松叶蜂是为害油松的一新种叶蜂,油松受害后,生长和发育受到影响,当针叶被取食95％以上时,可使油松生长率降低10．1％,连续2a-3a严重为害,可导致林木死亡。     

新松叶蜂的发生也防治

新松叶蜂,又名松黄叶蜂,属松叶蜂科。主要危害油松、赤松、华山松、马尾松、黑松、红松、云南松等松属的针叶。2005—2007年,祁门县马尾松受其侵害,幼虫大量取食针叶,严重影响马尾松的正常生长。     

新松叶蜂的发生与防治

新松叶蜂,又名松黄叶蜂,属松叶蜂科。主要危害油松、赤松、华山松、马尾松、黑松、红松、云南松等松属的针叶。2005～2007年,祁门县马尾松受其侵害,幼虫大量取食针叶,严重影响马尾松的正常生长。一、分布与危害情况新松叶蜂在我国主要分     

新松叶蜂的发生与防治

新松叶蜂,又名松黄叶蜂,属松叶蜂科。主要危害油松、赤松、华山松、马尾松、黑松、红松、云南松等松属的针叶。2005～2007年,祁门县马尾松受其侵害,幼虫大量取食针叶,严重影响马尾松的正常生长。一、分布与危害情况新松叶蜂在我国主要分     

新松叶蜂的发生与防治

新松叶蜂,又名松黄叶蜂,属松叶蜂科。主要危害马尾松等松属的针叶。马尾松受其侵害,幼虫大量取食针叶,严重影响马尾松的正常生长。     

广西新松叶蜂生活习性观察及其防治

广西新松叶蜂(Neodiprion guangxiicus Xiao et Zhou)属膜翅目、广腰亚目、松叶蜂科,分布广西(博白)、四川(盐源)、云南(南华、呈贡、丽江、永仁、广南、昆明、江川、宣威)。幼虫取食云南松针叶,食料不足时,亦取食华山松针叶,大发生时针叶被食光,余下枝梢及枝干,生长受到严     

松阿扁叶蜂的预防与治理

松阿扁叶蜂隶属于膜翅目,广背叶蜂总科,扁叶蜂科。主要危害油松、樟子松、赤松等树种的叶子。松阿扁叶蜂以幼虫取食针叶,大发生时针叶受害率达80%以上,枝梢上布满残渣和粪屑,林分似火烧一般。松阿扁叶蜂成虫多集中在晴天羽化,有补充营养的习性,在针叶上取食形成小缺刻。成虫受惊后落地假死,不久即飞翔逃跑,夜间不活动,对白光(日光灯)亦无反应。松阿扁叶蜂发生量     

靖远松叶蜂生物学及发生规律的研究

靖远松叶蜂（Ｄｉｐｉｏｎ ｊｉｎｇｙｕａｎｅｎｓｉｓ）是危害油松的重大森林害虫，１９９４年定为新种。该文对其形态、生物学特性、与环境因子的关系及主要天敌作了深入研究。此虫在山西省沁源，一般一年１代，以芯内预蛹（拟）在落叶层下越冬，成虫于６月间大量出现，少数有滞育现象，两年完成１代，雌雄性比为１：０．６每雌产卵１２０粒～２２９粒，有孤雌生殖现象，幼虫共８龄，每头幼虫取食针叶６０根左右、纯林、疏林、阴坡虫口密度大，靖远松叶蜂病毒（ＮＰＶ）、白僵菌、金头赘寄蝇、大山雀等２２种天敌是制约该虫种群数量的重要环境因素。     

南华松叶蜂的发生与防治

南华松叶蜂（Diprion nanhuaensis Xiao）属膜翅目、叶蜂总科、松叶蜂科。主要是以幼虫取食针叶，一头幼虫一生可取食针叶700cm左右，危害云南松、华山松、马尾松。通过10多年的观察与防治试验研究，基本摸清了南华松叶蜂的生活史、生物学特性、发生规律及综合防治技术．为南华松叶蜂的防治提供了科学依据。     

强优防治手段 加大科技含量 我省靖远松叶蜂防治工作取得重大突破

靖远松叶蜂是我省新发生的森林病虫害之一,去年,我省集中力量对交城、文水、沁源县和关帝林局境内发生的靖远松叶蜂(原名油松桦叶蜂)实施了飞机低容量喷雾防治和地面人工施放烟雾剂防治,取得了重大突破。防治面积共25.14万亩,其中飞机作业112架次,防治22万亩;地面施放烟雾剂16.7吨,防治3.14万亩。经效果检查,飞防区平均虫口减退率达97.4％,烟雾剂杀虫效果也达90％以上。我省靖远松叶蜂防治工作主要采取了以下措施:一、领导重视,精心组织。去年,各级政府和林业部门对靖远松叶蜂防治工作非常重视。针对我省大面积暴发靖远松叶蜂虫灾的情况,姜春云副总理明确指示:“要迅速采取措施扑灭虫灾”;林业部徐有芳部长、     

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。