Attacks by Ips typographus and Pityogenes chalcographus on Windthrown Spruces (Picea abies) During the Two Years Following a Storm Felling

Attacks by Ips typographus and Pityogenes chalcographus during the first 2 yrs after a storm were studied on 1848 windthrown spruces (Picea abies) in southern Sweden. In the first and second summer, 29% and 24%, respectively, of the spruces were attacked by I. typographus, while 21% and 44%, respectively, were attacked by P. chalcographus. High stumps were attacked less frequently than tops, broken trees and windfelled trees with root contact. In both years, trunks in gaps were preferred over those in stands. The proportion of windthrown trees attacked by I. typographus increased with stem diameter, whereas the opposite was true for P. chalcographus. Positive interspecific associations between the species were found on the lower, middle and upper third parts of the trees in the first summer and on the lower part in the second summer. The results are discussed with regard to forest protection and nature conservation.     

Studies on phenology and harmfulness of Aceria carvi Nal. (Acari: Eriophyidae) on caraway, Carum carvi L., in the Czech Republic

Caraway (Carum carvi L.) belongs to the traditional crops which have been grown in Bohemia since the end of the 19th century. Depressaria daucella (Denis and Schiffermüller) and Aceria carvi Nal. are two main pests of caraway in the Czech Republic. The latter becomes a serious problem in major caraway-growing areas. So far, no effective method for its control is known. The aim of this paper is to describe the phenology of symptoms of A. carvi infestation and damage caused by this pest. Our observation revealed that although A. carvi overwinters hidden within leaves of young caraway plants, the first symptoms are usually not visible before the start of flowering. Though the initial density of the pest is low, the mite population multiplies during the season when the pest attacks plant tissues and causes development of galls on leaves and flowers. Comparison of healthy plants and plants infested by A. carvi showed that infested plants had significantly more umbels but produced far fewer seeds, and the yield of caraway was thus substantially decreased. Recommendations for crop management methods to suppress the pest are given.Electronic Supplementary Material Supplementary material is available for this article at     

广东省黎蒴病虫害种类及危害情况调查

对广东省藜蒴病虫害种类和发生情况进行调查,共发现病害6种、虫害21种;初步确定了藜蒴主要病虫害种类为黎蒴枝枯病、黎蒴小蠹虫、英德跳虫脩、黎蒴榉祥蚧,危害严重时均可导致黎蒴死亡。介绍了4种主要病虫害的危害特点,并提出了相应的防治建议。     

Application of modal-based damage-detection method to locate and evaluate damage in timber beams

Modal-based damage-detection algorithms were used to identify the location of defects commonly found in timber and to estimate their severities. In this study, the authors propose modifications to an existing damage-detection algorithm for locating and evaluating damage by comparing the modal strain energy before and after damage using the first two flexural modes of vibration. Experimental verification was performed on pin-pin supported timber beams by employing the algorithms with extracted modal parameters using experimental modal analysis. Single and multiple cases of damage used to simulate pocket(s) of rot with various severities were inflicted by removing sections of timber beam specimens. The proposed damage indicator, computed from the first two flexural modes, was capable of detecting all damage locations. It was also able to estimate, with reasonable accuracy, the severity of damage in term of loss of sectional moment of inertia. The modified damage index method is generally reliable in detecting the location and estimating the severity of simulated defects in timber beams.     

A wavelet analysis-based approach for damage localization in wood beams

Free vibration testing was conducted to generate the first two mode shapes for damage detection in timbers. A wavelet transform was proposed to postprocess the mode shapes for damage pattern recognition. The wavelet used here was “db3.” The different damage severities, damage locations, and number of damaged areas were simulated by removing mass from intact beams. The results showed that the chosen wavelet db3 is suitable and that the wavelet coefficients are sufficiently sensitive to identify the existence of damage and its location in cases of different damage location, severity, and number. An edge distortion effect was apparent at the two computing edges where the wavelet coefficients were abnormally high. The wavelet coefficients showed dominant spikes around the damage locations and were zero everywhere else except the two computing edges. The dominant spikes coincided well with the damage location.     

基于GIS的洪灾损失评估方法

洪灾损失评估是防洪减灾领域的一项基础性工作。笔者在国内外洪灾损失评估信息系统研究的基础上，对现有的洪灾损失评估方法进行了探讨，论述了GIS技术在洪灾损失评估中的应用、特点及作用等，并提出了洪灾损失评估有待解决的问题及未来发展趋势，为科学、有效的采取防洪减灾措施提供一定的参考依据。     

烟蚜危害对烟草生理及生长发育的影响

１９８７￣１９９２年在网室内进行了烟蚜危害烟草的试验研究，结果表明：苗期开始受害的烟草，现蕾期叶片过氧化物同工酶活性加强，种类增多，随烟蚜侵害水平的提高，烟草叶片叶绿素含量下降，净光合强度减强，总氮和蔗糖含量升高，还原糖含量略有增加；株高降低，叶片数减少，现蕾期推迟８￣１５天。     

山西省棉花铃病的主要种类 为害损失及其防治策略的研究

山西省棉花铃病的主要种类为疫病(Phytophthora boehmriae)、红腐病(Fusarium moniliforme)和红粉病(Cephalothecium roceum),其中以棉铃疫病为优势种,在不同栽培方式中地膜田铃病重于露地。Bayes决策分析结果,次生病烂铃群体中67.4～89.1％的病铃来源于初生病铃,尤其是疫病铃。根据显著性检验结果,烂铃在棉株不同果枝上的垂直分布,地膜田可划分为第1～4和第5～7果枝两个层次;露地田可分为第1～2和第3～6果枝两个层次。该项研究明确了初生病菌与次生病菌侵染之间的数量关系及防治上的主要对象和靶区,为铃病的综合防治提供了理论依据。     

辩证看待麻雀残食庄稼

分析麻雀增多原因,提出雀灾是局部性的、麻雀是庄稼的卫士、麻雀不可随意捕杀等观点,对麻雀危害庄稼作了客观评价,提出低值粮食喂食、药物驱赶、使用凶猛动物粪便、引进天敌、适当捕杀等科学驱鸟方法。     

Survival and Growth of Picea abies Regeneration after Shelterwood Removal with Single- and Double-grip Harvester Systems

Three stands in Sweden were followed for 7 yrs to study the survival and growth of Norway spruce [Picea abies (L.) Karst.] regeneration after shelterwood removal with single- and double-grip harvester systems. The height of all seedlings within circular plots was recorded before and after final cutting. The tallest seedling and one randomly selected seedling on each circular plot were permanently marked and their annual height growth was measured each year during the period 1993-1999. No significant differences between single- and double-grip harvester systems were found with respect to their effects on regeneration density, survival or annual height growth. The annual height growth of the individual seedlings after shelterwood removal was significantly correlated with seedling height before shelterwood removal. Significant differences were found in annual height growth between seedlings with high and low vitality. Logging damage did not affect the annual height growth. Several practical conclusions were drawn. First, the choice of harvester system does not affect seedling height growth or survival after shelterwood removal. Secondly, the removal of a 200 m³ shelterwood with 200 stems ha^-1 does not seem to constitute a serious problem for seedling survival and growth. Finally, estimated vitality and seedling height both seem to be fairly good predictors of postrelease survival and growth.