雷竹竹织叶野螟幼虫的药物防治试验

竹织叶野螟是江西万年县近几年发生较为严重的雷竹林食叶害虫,为有效防治竹织叶野螟,采用喷洒药物与打孔注射药物方法对雷竹竹织叶野螟幼虫进行防治试验,结果表明:喷洒药物法,使用1%灭虫灵3000倍液,每666m2喷洒一次,防治效果可达97.1%左右;打孔注射药物法,首选药物为30%乙酰甲胺磷原液,每株2 mL,防治效果可达9...     

竹织叶野螟防治技术

竹织叶野螟在石首市桃花山地区与黄脊竹蝗混同发生,严重影响竹林生长。本文摸清了竹织叶野螟生物的生活习性和发生规律,探索了竹织叶野螟防治技术。     

竹织叶野螟的防治

竹织叶野螟隶属鳞翅目螟蛾科,主要是危害毛竹、刚竹、撑绿竹等多个竹种。该害虫在4～8月份幼虫吐丝将新长竹叶卷成竹苞取食,造成竹叶被吃光,严重影响竹鞭生长和次年出笋,甚至导致大面积竹林死亡。贵州省仁怀市竹林面积34,250亩,2008年该市撑绿竹发生20,000亩轻度、中度竹织叶野螟,基于对该害虫的治理,笔者总结出一些防治措施。     

不同药剂林间防治竹织叶野螟效果比较

竹织叶野螟是毛竹的重要害虫之一,严重危害时可将竹叶吃光,甚至导致竹子死亡。采用4种药剂进行了林间防治竹织叶野螟试验,结果表明,使用森得保可湿性粉剂1 500倍液、90%杀虫单可湿性粉剂1 000倍液、10%氯虫苯甲酰胺悬浮剂+有机硅1 000倍液、2.5%溴氰菊酯乳油1 000倍液进行林间喷雾,喷药后7 d,防治效果分别达68.95%、95.68%、92.99%、67.12%。杀虫单和氯虫酰胺防治效果显著好于森得保和溴氰菊酯,研究结果为竹织叶野螟防治药剂选择提供了依据。     

竹螟迁飞扩散习性的研究

竹织叶野螟(Algedonia coclesalis Wallker)是安吉县常见的四种竹螟中发生最多、为害最重的一种,约占总发生量的68％。年发生1—2代。以越冬代成虫迁飞扩散所产生的第一代幼虫吃食新竹竹叶。老熟幼虫在当地入土作茧越冬,为来年发生新虫害的虫源。安吉县毛竹林大小年区分明显,竹螟为害也随之出现一年重一年轻的现象。为了探讨竹螟迁飞扩散的规律和习性,以及与自然环境的主要关系,为     

竹腔注药防治竹织叶野螟的药效机理试验

用50%甲胺磷稀释液(甲胺磷:水=1:1)2ml注射竹腔防治竹织叶野螟进行药效机理试验结果表明:①注射后24小时,竹叶中的农药浓度就可杀死幼虫,持续时间为15天;注射后第4天,幼虫取食后20.2小时就死亡,速度最快,死亡率为100%;②幼虫死亡率、死亡速度不受虫龄影响。     

竹螟回归预测的初步研究

竹螟是重要的竹类食叶害虫,寄主有100多种,我国自北而南均有不同程度的发生,国外印度支那、缅甸、印度尼西亚也有分布。竹林受竹螟为害后,出笋量往往减少,眉围下降,而且受害竹重者死亡,轻者抗压、抗拉强度分别下降34.9％和27.7％。为给竹螟的综合防治提供科学的测报依据,笔者对本县一九七八年以来竹螟虫情的定点观察资料加以分析研究,结果表明:     

竹螟种群变化与预测预报技术的探讨

竹螟是浙江省安吉县的竹子主要害虫.近几年来,由于竹林经营集约化和开展综合防治,我们在竹螟测报调查中发现竹螟的种群结构发生了变化,竹金黄镰翅野螟5 a数量占竹螟总蛾量的53.8%,最高年份达78%.原来的测报规程是以竹织叶野螟的发生规律为依据制订的,这对病虫害的预测预报技术提出了新的要求.     

竹螟防治技术研究

在应用“竹腔注射”技术防治竹螟基础上,着重对其它防治方法进行了研究。研究结果指出,冬季垦复可降低竹螟土茧密度80％以上;高虫口密度时,采用蜜源地灭蛾可降低虫口150条/株以上,一块50亩左右的蜜源地天蛾可控制1500亩左右竹林幼虫的为害;一盏20瓦高压触杀灯可控制370亩左右竹林竹螟为害,并使幼虫虫口减少至103条左右/株。     

竹腔注射内吸性农药防治竹螟办法好

竹螟是蚕食竹叶为害竹类的主要害虫。受竹螟为害的竹林,轻则影响来年出笋,重则造成大片竹林枯死。据加兴地区一九七六年统计,因遭受竹螟为害为主导原因而造成枯死的毛竹达420余万株。防治竹螟实为生产上急需解决之严重问题。 几年来,在许多科研单位和专业科技人员的辛勤努力下,在摸清其生物学特性的基础上取得了竹螟综合防治的许多成绩,积累     

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。