杜鹃花枯梢病病原菌的研究

从有杜鹃花枯梢病的病株上分离到Ｐｈｙｔｏｐｈｔｈｏｒａ ｃａｃｔｏｒｕｍ,在温室内,病菌的游动孢子悬浮液喷布植株的幼嫩组织均能致枯梢病。嫩梢上的病斑在２￣３天内发展成浅褐色至暗褐色的病斑。游动孢子不会侵染无伤植株上的老组织,但侵入到植株体内的菌丝能穿过幼嫩组织而在老组织中定殖。老叶片上的楔形斑就是因病茎中的病菌穿过叶柄而产生的。病原菌在感病的寄主组织内部能产生卵孢子,病组织保温１２小时后,在被感染     

葡萄穗轴褐枯病的防治

<正> 葡萄穗轴褐枯病病菌为 Alter-nariaViticola,属半知菌亚门。病菌以菌丝体或分生孢子在病组织内越冬,春季开花前后病菌孢子传播侵染为害幼嫩的穗轴组织,发病开始先产生浅褐色湿润状病斑,并迅速向四周扩展,使整个分枝穗轴或主穗轴变成深褐色,     

樟子松枯梢病的侵染发生规律

在辽宁省章古台 ,松枯梢病 Sphaeropsis sapinea主要发生在樟子松 Pinussylvestrisvar.mongolica苗木和中老龄树木上 ,树龄越大 ,病害越重。病菌孢子在整个生长季节均能放散与传播 ,降雨节律和降雨量直接影响到孢子的扩散期、高峰期和数量。降雨量大的年份 ,孢子放散数量多 ,病害发生重。人工接种树木发现 ,从新梢伸长至针叶发育完全期间 ,病菌无需伤口即可直接侵入当年新梢并使之枯萎。病菌的侵入时期主要在 5月下旬至 6月下旬 ,此间也是化学防治的最佳时期。野外自然条件下 ,病害自 7月份开始发生 ,8月中下旬发展最快 ,1 0月份停止。樟子松是最易感染松枯梢病的树种之一。     

樟子松枯梢病的侵染发生规律

在辽宁省章古台，松枯梢病Ｓｐｈａｅｒｏｐｓｉｓ ｓａｐｉｎｅａ主要发生在樟子松Ｐｉｎｕｓ ｓｙｌｖｅｓｔｒｉｓｖａｒ．ｍｏｎｇｏｌｉｃａ苗木和中老龄树木上，树龄越大，病害越重。病菌孢子在整个生长季节均能放散与传播，降雨节律和降雨量直接影响到放散数量多，病害发生重。人工接种树木发现，从新梢伸长至针叶发育完全期间，病菌无需伤口即可直接侵入当梢并使之枯萎。病菌的侵入时期主要在５月下旬至６月下旬，此间也是     

秦皇岛地区杨树溃疡病的发生与防治

1发病特点 杨对溃疡病病原为群生小穴壳菌.病菌以菌丝在寄主体内越冬,翌年春气温升到10℃以上,菌丝开始活动,杨树表皮出现明显的病斑.分生孢子及子囊孢子也可在病组织内越冬.孢子借风雨传播,主要通过伤口侵入,也可由皮孔或表皮直接侵入.病害主要发生在树干和主枝上,不仅危害苗木和幼树,也能危害大树.轻则影响生长,重则引起枯梢,甚至整株死亡.病斑发生在树干基部0.2～2.5m高度范围内.感病植株多在皮孔边缘形成近圆形水泡状溃疡斑,初期极小,不明显,其后变大呈典型水泡状,直径约0.5～1.5cm.泡内充满灰褐色液体,水泡破裂,液体流出后遇空气变为黑褐色,并残留在病斑处.最后病斑干缩下陷,中央有一纵裂小缝.后期病斑上长出许多针头状黑色小点,受害严重植株,树干上病斑密集,并相互连片,病部皮层变褐腐烂.秦皇岛地区每年4月下旬开始发病,5月下旬至6月达到发病高峰,7～8月由于气温偏高,病势减缓并逐渐停止发展.     

松枯梢病菌侵入途径的超微观察

应用扫描电镜观察研究了松枯梢病菌在湿地松二年生针叶上侵入的可能途径。病菌的分生孢子在针叶表面能良好萌发，芽管长度可达孢子长度的１０—２０倍以上；许多芽管可伸进气孔腔中，未见有芽管直接侵入针叶的情况。在松枯梢病枯叶型和二年生针叶基部坏死型的症状类型中，气孔可能是病菌侵入的重要途径。     

松枯梢病菌侵入途径的超微观察

应用扫描电镜观察研究了松枯梢病菌在湿地松二年生针叶上侵入的可能途径。病菌的分生孢子在针叶表面能良好萌发，芽管长度可达孢子长度的１０－２０倍以上；许多芽客可伸进气孔腔中，未见有芽管直接侵入针叶的情况。在松枯梢病枯叶型和二年生针叶基部坏死型的症状类型中，气孔可能是病菌侵入的重要途径。     

葡萄霜霉病防治技术

1症状 葡萄霜霉病主要危害叶片,新梢、花蕾、幼果等幼嫩部分也受侵染。叶片感病后,在叶正面出现淡黄色半透明油渍状小斑点,逐渐扩大成黄绿色,边缘界限不明显,多为数个小病斑连成一个不规则或多角形的大病斑。在叶背面产生一层霜状灰白色霉状物,即病菌孢子囊梗和孢子囊。病斑后期变成淡褐色,干裂枯焦而卷曲,严重时叶片脱落。嫩梢感病后也...     

板栗疫病的综合防治

板栗疫病又称胴枯病,是影响幼龄板栗生长的最主要的传染病。病原菌为Phytophthora katsurae,属鞭毛菌亚门真菌。病原发育适宜气温为9℃—23℃。 一、发病规律及症状 病菌以卵孢子在病组织中越冬,翌年有降雨或灌水时形成游动孢子囊,产生游动孢子,随水流传侵染。在月平均气温18℃-27℃、相对     

德化县毛竹枯梢病发病与防治探讨

毛竹枯梢病是我国南方毛竹林的一种毁灭性病害。本研究通过实地调查和防治试验,对该病菌的发病时间规律和化学防治措施进行初步研究。结果表明,毛竹枯梢病在德化县主要危害当年的新生竹,该病的发病时间规律主要为每年的5月下旬至6月中旬,该病菌的子囊孢子飞散侵染,7月上中旬在新竹枝杈上出现病斑;50%多菌灵可湿性粉剂对毛竹枯梢病的防治效果较好,适宜浓度为1000倍液。另外,本研究还探讨了毛竹枯梢病的预测预报和综合防治措施。     

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.     

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。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.