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初雪 《绿色中国(A版)》2008,(8)
国家奖学金下来了,整栋宿舍楼都忙了起来。评选规则:家庭困难,学习刻苦,上学年成绩优异,无手机、电脑等高档消费品的同学。林非看了看,写了份申请书。几天后,拟定的人选公布出来了。林非看到自己在二等位置,笑了。回到宿舍,关了门,同学都不在,一口气喝了一大杯水,把寝室门关上,电视打开,沿着桌边走了一圈,又把电视关上,走了一圈,拿起杯子,放下,拿起一本书,又放下,最后躺在床上。 相似文献
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近年来,随着经济的飞速发展即国家可持续发展政策的不断深化和对环保工作的重视,各条高速公路在建设期间都投入了大量资金进行了绿化美化,有的甚至进行了综合景观设计,建成了景观大道,不但稳固了路基,保护了环境,美化了路容,还给司乘人员减轻了疲劳,降低了交通事故。下面就高速公路绿化工程设计阶段和施工及养护、管理等几个方面谈几点建议。 相似文献
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树活百千年而无语,默默地装点着群山、河流、田野、村庄与城市。树多就成林,林大即为森,巍巍群山有了茂密的树木,才会有长流不息的清清溪水滋润着的田野、村庄与城镇。有了树就有了水,有了水就有了田,有了田就有了粮,有了粮就有了人。可见,树与人类的生存有着密切的关系。森林,对于人类的重要性不言而喻,我们的城市也需要树木来装点。 相似文献
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近年来,国际木材非法采伐和相关贸易成为国际社会关注的热点问题,也引起了全球非政府组织和环境保护机构的关注。非法采伐不仅直接导致森林资源的严重破坏,诱发森林火灾和病虫害,影响生物多样性,而且侵占了木材生产国政府和社区的财政收入,加剧了地区贫困和利益冲突,扰乱了国际木材市场秩序,损害了合法经营者的利益,严重影响了全球生态、经济、社会的可持续发展。为此,中国政府采取了一系列有效措施,重拳打击国际木材 相似文献
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结合国家重点林业生态工程营造林综合核查,对山东省沿海防护林工程进行了调研,简要回顾了山东省沿海防护林的发展,介绍了所采取的工程措施,客观评价工程取得的成效,指出了存在的问题,并探索了沿海防护林的发展方向,提出了做好工程建设的合理化建议。 相似文献
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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。 相似文献
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森林冠层结构与功能及其时空变化研究进展* 总被引：16，自引：0，他引：16
林冠是森林与外界环境相互作用最直接和最活跃的界面层 ,同时 ,它本身又承载了森林生物多样性的主体部分。森林冠层研究的方法和技术在近些年取得了长足发展 ,从而促进了有关林冠结构与功能的研究。这些研究深化了人们对于林冠结构与光能截获以及群落干物质积累之间关系的认识 ,同时 ,对于森林冠层的物质循环和能量传输以及冠层内各营养级之间相互关系动态也有了更为深入的理解。考察森林冠层的结构与功能及其时空变化是深入理解整个森林生态系统的格局、过程及其运作机制的重要基础。 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1-4):457-469
The persistence of the four herbicides atrazine, hexazinone, lenacil and linuron was studied in forest nursery soils. The adsorption capacities of the soils for the chemicals were described by the distribution coefficients kj and koc. Due to the low content of organic matter in the soils the ka‐values were low, in several cases being <1 for hexazinone. Hexazinone also had the lowest k oc‐value (30) while the other substances had koc ‐values within the range 200–400. In some cases hexazinone showed great mobility under field conditions. The formula c=co‐kt1/2 was used to describe the disappearance of the herbicides from the various soils. The rate of degradation of the four herbicides correlated well with the rate of respiration in the same soils in laboratory experiments, and for linuron reasonably well also in field experiments. In the field experiments the herbicides penetrated the top soil layer. In the subsoil the risk of further transport downward to the drainage system or ground water increased, especially for hexazinone. Linuron as well as the fungicides maneb and tolylfluanid suppressed the decomposition rate of hexazinone in laboratory experiments. 相似文献
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刘宏明 《绿色中国(A版)》2005,(10):42-43
野生动物所有权是所有权的一种,它与其他所有权的区别在于客体的不同。文章阐述了野生动物的内涵,分析了野生动物的分类和野生动物与野生动物资源的区别。在明确野生动物含义的基础上,提出了野生动物所有权的概念,深入论述了野生动物所有权与野生动物资源所有权的差异和联系,并对野生动物所有权的主体、客体、内容进行了分析。 相似文献
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Pedro Ah Shenga Peter Bomark Olof Broman Dick Sandberg 《Wood material science & engineering》2017,12(4):257-262
The sawmill industry is a very important link in the Mozambique forest products value chain, but the industry is characterized by undeveloped processing technology and high-volume export of almost unrefined logs. The low volume yield of sawn timber has been identified as a critical gap in the technological development of the industry. To improve the profitability of the industry, there is thus a need to develop methods and techniques that improve the yield. In this paper, different positioning of logs prior to sawing and the possibility of increasing the volume yield of crooked logs by bucking the logs before sawing have been studied. A computer simulation was used to study the cant-sawing and through-and-through sawing of the logs to determine the volume yield of sawn timber from the jambirre (Millettia stuhlmannii Taub.) and umbila (Pterocarpus angolensis DC.) species. The optimal position, i.e. the position of the log before sawing that gives the highest volume yield of sawn timber for a given sawing pattern when the positioning parameters, offset, skew and rotation, are considered gave a considerable higher volume yield than the horns-down position. By bucking very crooked logs and using the horns-down positioning before sawing, the volume yield can be of the same magnitude as that obtained by optimal positioning on full-length (un-bucked) logs. The bucking reduces the crook of the logs and hence increases the volume yield of sawn timber. 相似文献
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Julia Janke Martina Bandte Christian Ulrichs Giselher Grabenweger Barbara Jäckel Hartmut Balder Carmen Büttner 《Journal of pest science》2009,82(1):47-53
The parasitoid wasp Pnigalio agraules (Wlk.) is a key natural enemy of the horsechestnut leafminer Cameraria ohridella Deschka and Dimić (Lepidoptera: Gracillariidae). As a basis for mark-release-recapture studies, aimed at investigating the
dispersal of this parasitoid in the field, adults of P. agraules were marked using a vertebrate-specific immunoglobulin (IgG). The marker was later detected by double antibody sandwich enzyme-linked
immunosorbent assay (DAS-ELISA). The IgG was either applied externally by spraying or internally by feeding an IgG-enriched
diet. Different concentrations of the marker were used and the influence of abiotic (climatic conditions, time elapsed between
marking and marker examination) and biotic factors (sex and age of the parasitoids) on the detection of the immunomarker was
tested. External marking by spraying led to more homogeneous labelling than feeding the marker. Parasitoids labelled with
0.25 mg rabbit IgG per ten individuals contained enough immunomarker to be easily distinguished from unmarked ones. Neither
the climatic conditions nor the sex or age of the insects had an influence on the detection of the marker. The IgG remained
well detectable during the entire lifespan of the parasitoids, which was not negatively affected by the marking procedure.
Serological marking can be used to investigate the dispersal behaviour of beneficial insects within mark-release-recapture
studies. 相似文献
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大兴安岭森林资源变化分析 总被引：11，自引：0，他引：11
阐述了人为破坏、过度采伐和自然森林火灾是引起大兴安岭森林资源变化的重要因子;通过对建国初到2002年大兴安岭森林资源在数量上和质量上的变化分析,得出了森林资源变化趋势。森林资源数量减少,且森林质量下降,大兴安岭的森林在经历着破碎化和年轻化的过程。 相似文献
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《Journal of Sustainable Forestry》2013,32(3-4):47-68
Summary Forest remnants in the Colombian Amazon, Andes, and Chocó are the last repositories of a highly diverse and endemic biota. Historical changes in the Colombian landscape have been dramatic, but the magnitude and rate of change has increased over the last half century, while conflict has consumed the capacity of Colombian society to respond to environmental threats. Academic experts in the study of the Colombian conflict have explored the social, political, and economic implications of the war. However, the environmental consequences of conflict are documented only when groups in conflict target salient economic resources. This paper presents the first analysis of the geographic distribution of forest remnants in relation to armed conflict in Colombia. Results show that guerrillas and/or paramilitaries range throughout areas of human encroachment into remnant forests. The policies promoted by Colombia's irregular armed forces range from “gunpoint conservation” rarely applied by guerrillas, to the rapid conversion of forests and crops to cattle ranches and coca (Erythroxylum sp.) plantations, following paramilitary occupation. Because the rates and extent of fragmentation are linked to such land use practices, armed groups may play a crucial role in determining the fate of Colombia's forests and their endemic biota. 相似文献
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湿地在我国分布比较广泛,在整个亚洲居于首位,但由于自然因素和人类的不当活动,我国的湿地面积锐减严重,且环境不断恶化。针对此种情况,本文详细论述了四川省湿地资源现状,并深入分析了造成此种情况的原因,最后给出了相应的治理对策。 相似文献