桉树青枯病病原菌的研究

桉树青枯病病原菌鉴定为青枯假单胞菌(Pseudomonas Solancearum Smith)。试验用各菌株青枯小种1号、生物型Ⅲ号。     

桉树青枯病研究的发现和创新

报导我国1991年后,桉树青枯病研究的发现和创新.即,桉树青枯病的流行是寄主为主导的流行病;病菌生理小种、生物型组成复什;病菌在病株残体和土壤中可存活3年以上,除从根部侵入外,还可从根茎部侵入;筛选出一批抗青枯病树种和无性系,并在生产中推广应用;研制成桉树青枯病流行测报模型;开创应用桉愈伤组织筛选抗病树种和无性系获得成功;应用基因工程技术培育桉树转基因抗病苗;应用外生菌根防治桉树青枯病取得一定效果.     

桉树青枯病流行区病菌小种和生物型的鉴定

从广东、广西、海南桉树青枯病流行区采集病菌标样51个菌株进行病菌和生物型的鉴定.结果表明:3个省(区)的桉树青枯病菌主要是小种1号;在广西、海南的菌株中,还有小种2号和3号病菌;生物型主要归属Ⅲ号,Ⅱ号和Ⅴ号出现频率较少;有的菌株生物型鉴定结果难归入Hayward的5个生物型中,可能有其他生物型.     

桉树青枯病的生物防治研究进展

文章综述了桉树青枯病的生物防治研究进展,包括利用拮抗细菌、内生菌、益生菌防治桉树青枯病等方面。指出了桉树青枯病的生物防治一方面应加强抗菌作用机制研究,提高防效稳定性;另一方面应加强林间应用技术的研究,综合运用多种生物因子,以期高效、简便、经济、安全地防治桉树青枯病。     

桉树青枯病发生规律与控制技术

桉树青枯病的病原为世界范围内广泛分布的茄拉氏菌[Ralstonia Solanacearum(Smith)Yabuuchi etal.],主要以生理小种1号、生化变种3菌系侵染为害。近10多年来由于桉树造林以无性系为主,在具备发病条件时,感病无性系的发病率可达30%~90%以上。由于茄拉氏菌生理小种1号为高温型菌系,在高温高湿和大风气候条件下易爆发成灾;桉树青枯病是单年流行病,有一定数量病原,气候因素有利于发病,桉树青枯病就大发生;易感病的树种1~3年生期间,青枯病可连年流行,随树龄增大病害流行逐渐缓慢,其中以1年生林发病率最高,4年生后基本不发病。桉树青枯病发生危害的程度具有明显区域差异,根据区域气候特点可以将桉树栽培区划分为高风险发生区、中风险发生区和低风险发生区。桉树青枯病的初侵染源为带菌土壤、带菌苗木和农家肥。在桉树青枯病高风险发生区,感病品系在沙土、壤土和粘土造林地均可严重发病,但在前作为易感农作物或以农家肥为基肥时,抗病品系也可严重发病;在中风险发生区,感病品系主要在坡下低洼积水处发病,在前作为易感农作物、以农家肥为基肥或以带病苗木造林的林地严重发病;在低风险发生区,感病品系主要在前作为易感农作物、以农家肥为基肥或以带病苗木造林的林地发生。目前,国内外对桉树青枯病仍没有有效的防治措施。根据桉树青枯病发生与流行规律,提出桉树青枯病可持续控制策略:实行植物检疫,培育无病苗木,减少病原菌初侵染源;采取科学营林技术,减少病原菌的种群数量,降低发病率;合理布局桉树品种(系),充分利用桉树良种资源;培育多类型抗病品种(系),以多品系混合造林减缓病原菌进化,形成专化型新菌系。并提出具体技术措施。     

我国桉树青枯病的研究概况

分析了我国桉树青枯病的研究概况,从桉树的介绍、我国森林青枯病的发现、青枯病病菌的生物学特性、青枯病的发病规律、桉树青枯病日益严重的原因,以及桉树青枯病的防治对策等方面进行阐论述,综述了目前的研究进展,提出了一些解决桉树青枯病灾情的建议,以期为后续研究提供参考。     

如何预防和防治桉树绝症——桉树青枯病

现在全国各地都在发展桉树速生丰产林,而桉树青枯病作为桉树的绝症,是桉树的生产和发展的严重障碍,给社会造成巨大的损失。因此,我们有必要认真地了解桉树青枯病,作好对桉树青枯病的预防和防治措施。     

桉树青枯病病原菌的分子鉴定及其致病性测定

对华南4个地区的桉树青枯病病原菌进行了分子鉴定和致病性测试研究,以期为有效预防其发生提供依据.分别对来源于不同区域的11株桉树青枯病病原菌进行分子鉴定和致病力强弱测试比较,11株病原菌与Ralstonia solanacearum序列形成支持率为86％分枝,表明其病原菌16S rRNA基因序列与Ralstonia solanacearum具有高度同源性.以桉树无性系DH32-29组培苗为材料,采用伤根法对11个菌株进行致病力测试,不同菌株间在致病性上差异显著(P＜0.01或P＜0.05),以发病高峰期、高峰期发病率和平均发病率进行K-均值聚类分析(K=3),结果表明来源于广东、广西、海南的各菌株间致病性存在差异,HY01、HY02、DA01、HP04菌株与HP05分为1类,DA02和DA03为第2类,而YJ01、HP01、HP02和HP03为第3类.对4个不同地区(采样点)的青枯病菌株平均发病率进行方差分析,结果发现来源广东阳江菌株致病性显著地低于其他来源菌株.不同地理来源菌株之间在致病性上无明显相关性,同一地区内同时存在着致病力强弱菌株,HP03的生物型4-1菌株与其他生物型3菌株在致病性亦无明显的差别.     

将两种抗病机制结合控制桉树青枯病的研究

以对桉树青枯病有防治效果的荧光假单胞杆菌（Pseudomonas fluorescens）WCS417r为对照,用水杨酸和产生PCA抗生素（phenazine-1-carboxylic acid）的荧光假单胞杆菌（P.fluorescens）2-79进行了桉树青枯病防治试验,并在此基础上,将水杨酸与2-79、WCS417r分别组合,将诱导抗病性和抗生作用结合起来共同控制桉树青枯病的发生.盆栽试验结果表明,采用菌液蘸根的方法,2-79和WCS417r分别比对照的发病率降低18.4%和33.8%,差异显著（α=0.05）.在组合防病试验中,经水杨酸、2-79、WCS417r分别处理后的桉树苗发病率分别比对照降低37.2%、42.9%和37.2%,而用水杨酸和生防菌共同处理（SA＋2-79,SA＋WCS417r）后的发病率则比对照分别低54.3%、51.5%,且比分别用三者单独处理的显著降低,防病效果显著增强.此结果表明,水杨酸的诱导抗病性与具有拮抗活性的生防菌结合,能显著提高防治桉树青枯病的效果.     

桉树青枯病测报模型的研究

根据桉树枯病发生及流行规律的定点观测资料，采用灰色系统理论的方法，建立了广东吴川林场和斗门县林业局试验林桉树青枯病预测模型；依发病率与相应的旬平均温度、相对湿度和降雨量，应用多元回归方法，建立了桉树青枯病多元线性回归预测模型．经检验和进行实际验证，证明上述模型均有较高的可信度．并表现为灰色系统模型的精度高于多元线性回归模型．     

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.