沙棘主要蛀干害虫危害特性及种群动态变化

沙棘木蠹蛾主要危害沙棘栽植树的根部和干部，红缘天牛同时危害沙棘栽植树和根蘖苗的干部，已成为宁夏沙棘林中两大主要蛀干害虫。通过对沙棘树不同高度范围内沙棘木蠹蛾幼虫和红缘天牛幼虫的调查发现，沙棘木蠹蛾幼虫主要分布在地下根部和干部40～120cm的范围内，而红缘天牛主要分布在树干40～120cm的高度内。红缘天牛幼虫数量随时间变化大致呈现向树干上部增加的变化趋势。沙棘木蠹蛾幼虫数量随时间变化呈现明显的向根部转移的趋势，7月末，有近98％的幼虫在根部危害。之后，由于初孵幼虫的大量出现，使干部幼虫数量急剧增加，越冬前，虽然有部分转移至根部危害，但到9月末仍有近43％的幼虫停留在树干40～120cm处越冬，直到次年越冬结束。沙棘木蠹蛾和红缘天牛在沙棘树干部40cm以上危害位置的较大重叠，必然造成它们在时间、空间和营养上的激烈竞争。     

沙棘主要蛀干害虫研究概述

沙棘木蠹蛾和红缘天牛是沙棘的两种主要蛀干害虫,主要以幼虫危害沙棘的根部和干部。沙棘木蠹蛾近年在沙棘种植区大面积暴发,红缘天牛也多伴随发生。目前,从生物生态学特性、成灾原因、监测和防治措施等方面,对这两种害虫的研究已取得了很大的进展。本文对沙棘木蠹蛾和红缘天牛不同发生地的生活史、危害特性、暴发成灾的主要原因及所采取的主要防治方法进行概述,以期能进一步更有效地促进其危害控制的研究和应用。     

野生沙棘平茬除虫复壮技术及效益评价

红缘天牛与沙棘木蠹蛾是严重危害沙棘的两种蛀干害虫。平茬除虫复壮是控制沙棘蛀干害虫危害,恢复并提高野生沙棘林的经济及生态效益的必要措施。通过沙棘年龄与挂果指数的回归曲线,估算出平茬的适宜年龄为8龄。平茬技术方法简单,平茬后的萌生苗至少在两年内不受蛀干害虫的危害,平茬第3年比平茬前每公顷多产果840.9千克,尚可获得显著的生态效益。     

沙棘木蠹蛾在辽宁省发生危害原因及对策

沙棘木蠹蛾(Holcocerus hippophaecolus)属鳞翅目、木蠹蛾科,1986年在辽宁省首次发现,2001年起,沙棘木蠹蛾在辽宁省西部暴发成灾,致使沙棘林出现大面积死亡现象。并呈继续扩散蔓延趋势,已造成了巨大的经济损失。1沙棘木蠹蛾的发生与危害状况沙棘木蠹蛾在辽宁省主要发生在朝阳市建平县、北票市;阜新市的阜新县、彰武县。根据实地调查测定,朝阳地区所有沙棘林均受到沙棘木蠹蛾的危害,多数林分沙棘个体死亡率达50%以上,有虫株率80%以上,虫口密度20头以上。2沙棘木蠹蛾发生危害的原因分析2.1沙棘木蠹蛾的生物学特性沙棘木蠹蛾4年1代,以幼虫在被…     

沙棘木蠹蛾生物学习性及防治研究

沙棘木蠹蛾(Holcocelus vicarius walker)是目前沙棘林区主要蛀干害虫，造成沙棘大面积死亡。该虫2年1代跨3个年度。其防治方法主要用磷化铝堵塞虫孔熏杀幼虫，化学药剂喷杀初孵幼虫及灯诱、性诱、人工捕杀等实行综合治理，效果可达90％以上。文中还记述了沙棘两种主要蛀干害虫沙棘木蠹蛾与沙柳木蠹蛾在幼虫与成虫形态上的主要区别，便于在防治工作中的识别。     

沙棘主要钻蛀性害虫综合防治技术

对沙棘钻蛀性害虫沙棘绕实蝇、沙棘象鼻虫、红缘天牛、木蠹蛾类，采用地面喷粉、林冠喷雾、干部注药的化学防治措施与选择混交类型、平茬复壮、绝花绝果、保护天敌等营林、生态、生物防治技术，可有效地控制沙棘钻蛀性害虫的危害。     

沙棘木蠹蛾生物学特性的初步研究

沙棘木蠹蛾主要为害沙棘，亦加害榆，山杏，沙枣等，该虫在我区凉成４年－代跨５年，以幼虫越冬，老熟幼虫于６月初入土蛹，成虫于６月末始见羽化，７月达羽化盛期。此虫产卵量少者２７粒，多者６２５粒，７月初始见初孵幼虫，幼虫有１３个龄期。     

沙棘主要病虫害及防治

1．沙棘的病虫种类及危害性？沙棘病虫害种类较多，其病害主要有沙棘腐朽病、沙棘烂皮病、沙棘干枯病、沙棘叶斑病、沙棘缩叶病、沙棘猝倒病、菟丝子等；沙棘虫害有沙棘象、沙棘实蝇、沙柳木蠹蛾、柳干木蠹蛾、红缘天牛、栎黄枯叶蛾、黄褐天幕毛虫、沙棘巢蛾、舞毒蛾、沙枣尺蛾、兰目天蛾、沙棘木虱、华北蝼蛄、黑绒鳃金龟等。沙棘病虫害如不及时防治，对沙棘园及人工林造成大量减产；有的危险性病害如国外传来的沙棘干枯病，目前已在国内沙棘产区大量蔓延，造成人工林成片死亡。在虫害方面，沙棘象、红缘天牛、沙棘蝇等种实害虫和蛀干害虫危害也很严重，1990年铜川发生大面积沙棘象危害，种实被害率达80％以上，当年沙棘种子颗粒无收，     

沙棘木蠹蛾生物学特性及综合防治

以研究山西沙棘木蠹蛾生物学特性及防治为目的,通过室内外观察沙棘木蠹蛾形态特征及生活习性,发现该虫在山西4年1代,老熟幼虫于5月上旬开始结茧化蛹.成虫羽化从6月中旬开始,7月中旬达到高峰期,8月下旬进入末期.雌成虫羽化当天即可交尾且多次产卵,平均产卵量为76粒.利用该虫生物学特点提出了综合防治方法,并为沙棘木蠹蛾的有效控制提供有价值的信息.     

沙棘主要钻蛀性害虫综合防治技术

提出对沙棘钻蛀性害虫沙棘绕实蝇、沙棘象鼻虫、红缘天牛、木蠹蛾类,采用地面喷粉、林冠喷雾、干部注药的化学防治措施与选择混交类型、平茬复壮、绝花绝果、保护天敌等营林、生态、生物防治技术,在生产实践中可有效地控制沙棘钻蛀性害虫的发生危害。     

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。