百菌清对杨树烂皮病的抑制机理初步分析

为了更科学有效的防治杨树烂皮病，文章初步分析了百菌清对杨树烂皮病的抑菌机理，采用固、液体培养法，测定百菌清对杨树烂皮病菌丝生长、生物量、菌丝体内丙二醛和可溶性蛋白质含量的影响。结果显示，百菌清对杨树烂皮病菌丝生长及生物量有显著的抑制作用；能增大细胞膜脂质过氧化程度，导致丙二醛含量增多；并能抑制菌丝体内可溶性蛋白质合成，使体内蛋白质含量降低。     

中生菌素对杨树烂皮病的抑菌机制初报

为了研究中生菌素对杨树烂皮病的抑菌机制,采用固、液体培养法,测定中生菌素对杨树烂皮病菌丝生长及生物量的影响,并测定其对菌丝体内可溶性蛋白质和丙二醛含量的影响。结果表明:中生菌素对杨树烂皮病菌丝生长及生物量有明显的抑制作用,并抑制菌丝体内可溶性蛋白质合成,增大细胞膜脂质过氧化程度,导致丙二醛含量增大。证实中生菌素作为一种广谱杀菌剂,可应用于林业病害的防治,为杨树烂皮病科学防治提供一定理论基础。     

几种拮抗菌对杨树烂皮病菌的影响

Trichoderma3个菌株及Chaetomium sp.与杨树烂皮病菌(Cytospora chrysosperma)的对峙培养试验的结果表明:试验中采用的Trichoderma viride1,Trichoderma viride2,Trichoderma harzianum及Chaetomium sp.对杨树烂皮病菌都有一定的抑制效果,其中Trichoderma viride1对病原菌的相对抑制效果最好,且其相对抑制效果随着时间的增加而增长,在74h时达到最高,抑制率可达到64.55%;其相对抑制效果也达到最大,为11.49;其它3个菌株的相对抑制效果在对峙培养74 h时也达到最大,介于1.77~4.15之间。     

杨树枝枯病病原菌的初步研究 Ⅰ.病原菌形态和致病性

杨树烂皮病为害杨属各个种,分布普遍。是苗圃和幼林的重要病害之一,也是成年树枝枯的主要原因。我国杨树烂皮病病原菌过去的报导是Valsa sordida Nit.北京地区引起杨树烂皮和枝枯的病原菌,除Cytos-     

7种杀菌剂对杨树烂皮病、溃疡病病菌的室内毒力测定

室内测定了7种杀菌剂对杨树烂皮病病原菌金黄壳囊孢菌Cytospora chrysosperma (Pers.)Fr.、溃疡病病原菌Dothiorella gregaria Sacc.的毒力.72 h含药平板对抑制金黄壳囊孢菌的菌丝生长毒力最强的有10％苯醚甲环唑水分散剂、250 g/L嘧菌酯悬浮剂,EC50值依次为0.0006,0.020 2μg/mL;其次为70％甲基托布津可湿性粉剂,EC50为0.195 8μg/mL;最弱的是树乐粉剂,EC50为319.658 0μg/mL.48 h对杨树溃疡病病原菌的毒力最强的有250 g/L嘧菌酯悬浮剂、10％苯醚甲环唑水分散剂,EC50依次为0.072 2,0.090 4μg/mL;其次为70％甲基托布津和50％多菌灵可湿性粉剂,EC50依次为2.5603,19.0454 μg/mL;树乐最弱,EC50为366.415 7μg/mL.同一药剂对杨树烂皮病菌的毒力强于溃疡病菌.     

走马芹提取物对杨树烂皮病的抑制作用研究

对走马芹的80%乙醇超声波提取物对杨树烂皮病原菌的抑制作用进行了研究,实验结果表明:不同浓度的走马芹提取物均对杨树烂皮病的病原菌产生了较强的抑制作用并呈对数增长趋势。     

绿木霉菌株T43对松烂皮病菌的抑制效果及其抑菌机理

通过对峙培养和非挥发性代谢产物对病原菌生长的抑制]作用,对引进绿木霉(Trichoderma virene)菌株T43及其抑菌活性物质对松树烂皮病菌(Cenangium ferruginosum)的抑制效果进行了研究;从菌株T43发酵液乙酸乙酯提取物对松树烂皮病菌的3种保护酶(SOD、CAT和POD)活力影响的角度,初步探讨了提取物对病原菌的抑菌机理.研究结果表明:对峙培养48 h后,菌株T43对松烂皮病菌相对抑制效果为1.00,72 h后菌株T43与病原菌形成明显的拮抗线,并抑制病原菌的生长.菌株T43乙酸乙酯提取物对病原菌株的室内生长抑制率为60.50％.菌株T43发酵液乙酸乙酯提取物对病原菌的3种保护酶具有明显的抑制作用.     

两种抑菌剂对杨树烂皮病的抑制作用研究

选用广谱抑菌剂百菌清和生物抑菌剂中生菌素,研究它们对杨树烂皮病的抑制作用.结果 表明采用生长速率法,通过室内抑菌试验,确定百菌清600倍稀释液和中生菌素800倍稀释液对杨树烂皮病的抑制率均达到85％以上,证实中生菌素对杨树烂皮病的抑菌效果高于百菌清.期待为杨树烂皮病病害防治提供一定的理论基础,为杨树烂皮病生物防治提供一...     

江苏杨树烂皮病发生状况调查及化学防治试验

通过对江苏省杨树烂皮病发生状况调查发现,在新沂,六合和仪征3个地区有杨树烂皮病发生。在调查的4 417株杨树中,平均发病率占11.32%;杨树烂皮病的发生与树种、树龄、地形、土壤、坡向以及虫害的关系均较密切。苗圃内不同药剂、配比度对杨树苗刮皮后的涂药试验发现,吡唑醚菌酯500,1 000,1 500倍液3种配比度的防治效果均在88%以上,嘧菌酯500倍液的防治效果高于80%。说明在苗圃用吡唑醚菌酯1 000倍和1 500倍液防治杨树烂皮病,可以取得良好的防治效果。     

杨树内生真菌的分离和拮抗生防菌的筛选

从健康杨树植株的叶(芽)、皮、枝中分离获得154株内生真菌,经形态观察分类鉴定归属于3个目、5个科、13个属中.利用两点对峙培养拮抗试验、孢子萌发试验和人工接种试验,从中筛选杨树烂皮病病原菌的拮抗菌.试验结果表明所获内生真菌(4属)菌株对病原菌菌丝生长和孢子萌发均存在不同程度的抑制作用,其中,青霉属真菌(Penicillium sp.)的菌株拮抗效果表现最明显.青霉菌可迅速对病原菌菌落包围、覆盖,从而使植物病原菌生长受到抑制,孢子萌发试验中,3 d的培养滤液就可对病原菌孢子萌发产生抑制作用,表现出一定的生防潜能.     

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.     

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。     

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.     

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.