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1.
Summary The defensive mechanisms which protect ladybird beetles (Coccinellidae) against predators are reviewed. Besides behavioural mechanisms, such as thanatosis and reflex bleeding, chemical defence mechanisms are playing a prevalent role. Indeed, ladybirds are protected not only by their smell, but also by repulsive alkaloids, most of which are considered to be of autogenous origin. In a few cases, dietarily-acquired substances are also involved. Particular emphasis is laid on the repellent alkaloids which are contained in the haemolymph of many species. The structures of 34 nitrogen-containing compounds isolated so far are presented, and their distribution within the family is discussed in the light of the most widely accepted classification of these beetles. To conclude, the mode of release of the alkaloids, their variation through the life cycle and their repellent and toxic properties are discussed, as well as the few biosynthetic data yet available.  相似文献   

2.
我国城市垂直绿化现状与垂直绿化新技术   总被引:26,自引:0,他引:26  
虽然我国各城市开展城市垂直绿化推广工作,取得了不少成效,但是依然存在着垂直绿化技术和植物种类单一、效果有待改善等问题。近年来,国内外出现了不少新的垂直绿化技术,若能借鉴、选择性地进行应用,对我国城市垂直绿化工作必定起促进作用。介绍了几种较新的垂直绿化技术,以供参考。  相似文献   

3.
The commercial tuna fishery in the Eastern Tropical Atlantic is based on harvests from three species of tuna: Yellowfin, Skipjack, and Bigeye. Two models are developed to examine the bioeconomics of this fishery. In the first model, species are presumed ecologically independent and selectively harvested. In the second model, two of the species (Yellowfin and Skipjack) are assumed to be interspecific competitors and jointly harvested independent of the third species (Bigeye). Data on landings, effort, cost, and revenue are assembled allowing estimates of the bioeconomic parameters for the model where all species are independent and selectively harvested. Open access and bioeconomic equilibria are identified for a combination of cost and discount rates. The pristine, open access, and bioeconomic equilibria are also determined for the multispecies model based on parameters from the single species (independent) models and plausible values for interaction and joint production coefficients. Equilibria are compared, and management policies from a single- and multispecies perspective are explored.  相似文献   

4.
We examine the choice of policy instruments (price, quantity or a mix of the two) when two pollutants are regulated and firms' abatement costs are private information. Whether abatement efforts are complements or substitutes is key determining the choice of policies. When pollutants are complements, a mixed policy instrument with a tax on one pollutant and a quota on another is sometimes preferable even if the pollutants are identical in terms of benefits and costs of abatement. Yet, if they are substitutes, the mixed policy is dominated by taxes or quotas.  相似文献   

5.
南岳珍稀濒危动物的调查研究   总被引:1,自引:0,他引:1  
在南岳野生动物中,珍稀濒危动物共有28种,一级1种,即黄腹角雉TragopanCaboti;二级23种,其中哺乳类5种,鸟类15种,两栖类2种;中国生物多样性保护行动计划优先保护名录二级动物1种;中国优先保护动物中国特有种(A级)4种.本文主要介绍了它们的分类位置、形态特征和在我国的分布,根据南岳现有的资源状况,提出了保护措施与对策.  相似文献   

6.
With increasing concern over chemicals that are potential health hazards at low levels, determination of limits of detection have undergone considerable scrutiny. Most traditional detection limit estimators suffer from extensive statistical and/or conceptual limitations. In this paper, traditional detection limit estimators are described and critically evaluated. Using the terminology of Currie (1968), methods are categorized into decision limits versus detection limits. The methods are further categorized into single concentration design versus calibration design methodologies. While the single concentration design methods are useful for fixing ideas and clarifying definitions, they are shown to be extremely limited in practice since dependence of variability on concentration can neither be estimated or incorporated. Calibration-based detection limit estimators are described, compared and contrasted. Generalizations to non-constant variance, multiple future detection decisions and simultaneous control of Type I and II errors are provided. The various calibration-based methods are illustrated using real data and experimental design issues for detection limit studies discussed.  相似文献   

7.
降解四氯乙烯厌氧菌的分离和特征   总被引:4,自引:0,他引:4  
从降解四氯乙烯沼气污泥富集培养物中分离得到4株厌氧菌,其中2株为弧菌(Vibrio),其细胞弧状,分别端单生,丛生鞭毛;1株是杆菌(Bacillus),其细胞杆状,G-,无鞭毛和芽孢;1株为甲烷八叠球菌(Methanosarcina),其细胞球状,成堆排列.4株菌均可以甲醇为碳源,并具有不同强度降解四氯乙烯的活性.  相似文献   

8.
本文提出利用环境功能指数对城市环境功能区的环境功能进行评估,设计了相应的评估方法,以马鞍山市七个环境功能区为例进行了实例分析,讨论了各功能区的环境功能变化趋势,并提出了相应的对策与建议。  相似文献   

9.
Some intrinsic properties of differential equation models of ecosystems are formulated. The properties, which are long-termed, are classified into fundamental, stability, and sensitivity substructures. An aspect of the ecological term “resilient” — asymptotic stability uniformly for all small parameter variations — is introduced in a mathematical setting. In the sensitivity substructure, bounded sensitivity and continuity of sensitivity with respect to solutions are recognized as intrinsic properties. Illustrations of these two properties are given.  相似文献   

10.
城镇绿地对空气质量的影响--以中山市小榄镇为例   总被引:15,自引:0,他引:15  
对中山市小榄镇公园、街道、居住区等不同地区的空气质量进行了测定.结果表明:公园、苗圃、金菊花园、镇府大院和小榄中学等绿化好、总绿量大的地带,CO2浓度[Ψ(CO2)/10^-6]和含菌量(n/m^-3)明显较低,负离子浓度明显较高;街道、新永路民居、商场、工厂、车站和果菜批发市场等绿化差、总绿量小的地带,Ψ(CO2)/10^-6和含菌量明显偏高,负离子浓度明显偏低.街道上空的Ψ(CO2)与车流量之间有极显著相关关系Ψ(CO2)与人流量之间相关关系不显著.  相似文献   

11.
系统地介绍了西方国家常用的1种评价环境物品(公共物品)的方法——条件价值法。在大量文献和作者已有研究的基础上,解释了环境物品的特征和价值含义,综述了条件价值法的概念、特点和总体框架内容,分析了该方法中出现的偏差类型,总结了该方法在国际国内的已有应用,提出其应用潜力和应用前景  相似文献   

12.
闽江口湿地的鸟类研究   总被引:24,自引:1,他引:23  
1998-2000年对福建省闽江口湿地的鸟类资源进行了调查,共记录鸟类86种,隶属11目23科,其中古北界鸟类59种(68.6%),东洋界鸟类27种(31.4%),区系组成呈现南、北鸟类混杂分布,以古北界鸟类为主的特征,留鸟12种,占鸟类总数13.9%;迁徒鸟74种,占86.1%。该湿地鸟类的多样性表现出明显的季节性,迁徒季节鸟类的各类和数量都最多,繁殖季节则最少,该湿地有国家二级保护鸟类9种,中日修鸟保护协定名录中的鸟类49种,并对鸟类资源的保护和管理提出了建议。  相似文献   

13.
采用点格局分析法对不同海拔的椴树(Tilia miqueliana Maxim.)种群进行分布格局及其种间关系进行了研究。结果表明:整体上群落内以中龄树个体数为最多,小树次之,成年树个体最少。随着海拔的增加可以看出:小树(d≤5 cm)随着海拔的增加而减少,中树(5 cm20 cm)的规律不明显;椴树种群的空间分布格局与空间尺度(25 m内)有密切关系,在较小的空间尺度上倾向于非随机分布,具有明显的空间相关性;在>15 m或25m的某临界尺度时却倾向于随机分布,同时空间关联变得微弱。随着海拔的增加,各物种聚集分布的尺度有逐渐减小的趋势。种间关系随着海拔的增加,物种间的正相关尺度有增加的趋势。  相似文献   

14.
Indices based on network theory are often used to describe food web functioning. These indices take as input food web flows that are estimated based on merging of (scarce) data with linear inverse methods (LIMs). Due to under sampling, most food webs are highly uncertain and can only be quantified within a specific uncertainty range. The linear inverse method (LIM) can estimate food web flows using a variety of techniques, e.g. the parsimonious or minimum norm (MN) solution, which selects one food web, based on a quadratic minimization technique or the Monte Carlo solution where a finitely many random solutions are generated which are then averaged. We use the Monte Carlo approach (MCA) to estimate the values of several indices from four published food webs, the Gulf of Riga for the autumn, summer and spring seasons, and the Takapoto atoll system. We first show that network indices are much better constrained than the uncertain food webs from which they are calculated. Therefore, even in the face of food web uncertainty, they are robust estimators of food web functioning. We then use the MCA-derived network indices to generate cumulative density functions for each index. These serve to compute the probabilities of the MN indices estimates being an extreme solution as compared to the median values. Our findings show that 82% of the MN solutions are smaller than the MCA solutions, and 63% of the network indices are significantly under-estimated.  相似文献   

15.
中国及邻近地区核果茶属植物的初步订正   总被引:2,自引:0,他引:2  
对中国及邻近地区的42种及2变种核果茶属植物进行了初步的分类学订正,确认为20种、4变种(中国有16种、4变种),其中包括1个新种、8个新组合和2个新记录种。有25个合格发表被作为相应的种或变种的异名而归并.  相似文献   

16.
Suspendend solids (SS) are important parameters in the assessment of potential effects of emissions out of sewer systems. This is due to the fact that many pollutants are transported with particles in the sewer systems and therefore are emitted into receiving waters. In this paper, significant emissions in commonly applied sewer systems (combined sewer system [CSS], separate sewer system [SSS]) are mentioned, and typical concentration ranges of SS are listed. Furthermore, data from selected pollutants (lead, polycyclic aromatic hydrocarbons [PAH]) are collected and concentration ranges in typical flow types of the sewer systems are calculated. In the second part of the paper results from pollution load simulations are introduced. The calculations are based on assumptions from literature and were conducted in a hypothetical catchment. Main interest was the comparison of emissions out of SSS and CSS, shown for selected parameters SS, lead and PAH. Results of the pollution load simulation show that emissions for surface runoff related compounds like lead are extremely high in the SSS in comparison to the CSS. This is mainly reasoned by the high elimination rate in the waste water treatment plant (WWTP). In summary, a general answer, which sewer system emits higher pollution loads is not possible. It is extremely dependent on the considered substance and its specific properties and resulting behaviour in the sewer systems. For a first estimation, new classes of substances are distinguished considering their origin (surface runoff versus dry weather flow) and their elimination capacity in the WWTP.  相似文献   

17.
Songs of the humpback whale Megaptera novaeangliae were recorded and analyzed from Grand Turks in the Bahamas to Venezuela. The design features of the song are as follows. The basic song evolves through a series of different sounds in a fixed order. The song is produced only in the winter tropical calving grounds, just before the whales arrive on the banks. Redundancy is high in that syllables, motifs, phrases and the entire song are repeated. Low, intermediate, and high-frequency sounds are scattered throughout the song. One sound is associated with blowing. The song appears to be partially different each year and there are some differences within a year between banks which may indicate that dialects are present. It is suggested that songs from other populations are quite different. The apparent yearly changes do not occur at one point in time. Only single individuals produce the song and they are hypothesized to be young, sexually mature males. The implications of these various design features are discussed.  相似文献   

18.
南岳具有重要开发利用前景的大型真菌   总被引:1,自引:0,他引:1  
报导了南岳44种重要的大型真菌,阐述了它们的开发利用价值,提出了合理开发利用和保护的意见.  相似文献   

19.
我国大气环境毒理学研究新进展   总被引:2,自引:0,他引:2  
对大气环境中重要污染物的毒理学作用及其机制方面的文献进行综述。首先,总结了细颗粒物(PM2.5)和纳米颗粒物对呼吸系统和心血管系统毒理学作用及其机理方面的研究;然后,评述了二氧化硫(SO2)对基因表达的影响及内源性SO2生理作用方面的研究,提出SO2既是一种全身性毒物,又是一种新型信号分子的新观点;对大气环境致癌物,特别是有关苯并芘致癌作用分子机制的研究进行讨论;对大气中臭氧和光化学烟雾对健康影响的研究作了评述;最后,对室内空气污染物尤其是甲醛的毒性作用及其机理方面的最新研究进行了评论。  相似文献   

20.
菜田土壤氮素淋失及其调控措施的研究进展   总被引:11,自引:1,他引:11  
从菜田中硝态氮的动态变化、土壤氮素的矿化、硝态氮对地下水的影响等几方面概述了近年来国内外的研究进展,介绍了渗漏测定计法、土壤溶液提取器和15N同位素示踪技术等3种测定土壤氮素淋失的研究方法其应用前景;论述了影响菜田土壤氮素淋失的主要因素和降低菜田土壤氮素淋失的丰要调控措施;提出了今后菜田土壤氮素淋失应加强的研究方向。  相似文献   

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