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排序方式: 共有208条查询结果,搜索用时 15 毫秒
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本文基于中国、西北欧的主要植物油价格以及马来西亚棕油价格、库存、产量的月度数据,研究其波动关联性。研究结果表明,最近7年和20世纪80年代的价格波动较为剧烈,西北欧市场植物油价格在过去30多年中没有明显增长趋势;季节性变动呈变弱趋势,豆油的季节性变化相对小;在棕榈油市场,投机对价格波动的影响较弱,但最近7年开始加重;不同地区、不同产品的价格关联性强,但菜籽油在不同区域市场之间的关系相对弱一些。 相似文献
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Nicholas Koutsikos Leonidas Vardakas Stamatis Zogaris Costas Perdikaris Olga‐Ioanna Kalantzi Alcibiades N. Economou 《水产资源保护:海洋与淡水生态系统》2019,29(3):409-423
- Rainbow trout is ranked as one of the world's worst alien invasive species; in Europe, however, the extent of established populations remains localized and poorly reported. This study aims to assess rainbow trout establishment in Greece and explores the factors affecting the success or failure of establishment.
- Fish samples and site‐specific environmental attributes collected during the past 17 years (2001–2017) were analysed. All available literature on the distribution patterns of rainbow trout were reviewed in parallel to those of the Greek native Salmo trout species and demographic criteria were applied to infer potential establishment.
- Data indicating poor persistence of populations and population structure support the argument that recruitment of rainbow trout is extremely limited in Greece. Lack of suitable environmental conditions is not the main factor leading to the failure of rainbow trout to become established. Genetic factors affecting reproduction, possibly through a combination of outbreeding depression resulting from the admixture of unrelated intraspecific lineages, and maladaptive behaviour resulting from domestication in captivity, remain probable causes of poor establishment for the Greek populations of rainbow trout.
- Overall, the threat of rainbow trout as a highly invasive species in Greece is lower than suggested by recent risk assessments.
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我国马铃薯油炸专用型品种匮乏,生产种植品种主要是大西洋和夏坡地。利用西欧种质资源配制组合,探讨选育适合黑龙江省农业生态条件油炸专用型马铃薯品种可能性。被测试无性系12个,以炸片品种大西洋和炸条品种夏坡地为对照,在哈尔滨和讷河两点评价被测无性系产量和油炸品质表现。JT04-7-23适合薯条加工,该无性系薯块长形,总产量、商品薯产量、比重与炸条品种夏坡地相当,但炸条颜色优于夏坡地。T11-197-1适合炸薯片,块茎圆形,总产量和商品薯产量略高于对照大西洋,比重和炸片颜色略逊大西洋,但仍在可接受范围内。还选出T10-6-14和N10-4018,可用作油炸品种亲本。试验结果表明,利用西欧马铃薯种质资源可选育适合黑龙江农业生态条件的油炸马铃薯品种。 相似文献
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Marija Marković Vladimir IvovićTijana Štajner Vitomir DjokićIvana Klun Branko BobićAleksandra Nikolić Olgica Djurković-Djaković 《Comparative immunology, microbiology and infectious diseases》2014
To contribute to the insight into the worldwide population structure of Toxoplasma gondii, we genetically characterized a total of eight strains isolated from intermediate hosts including humans, sheep and pigeons in Serbia. Although parasite DNA was detected in 28.2% (60/213) of the human samples from 162 patients serologically suspected of active toxoplasmosis, as well as in 5/7 seropositive pigeons and in 2/12 seropositive sheep examined, multilocus PCR-RFLP genotyping, using SAG1, 5′SAG2, 3′SAG2, GRA6, 5′GRA7 and 3′GRA7 as markers, was successful in only four human isolates (of which one was isolated from both the bronchoalveolar lavage fluid and blood samples of a single patient), one sheep and three pigeons. Of the eight isolates, five were type II (62.5%), one was type III, one was atypical, and one had a type I allele at GRA6 as the single locus genotyped. Although type II, as elsewhere in Europe, predominated, these results may suggest a higher genetic diversity of T. gondii in Serbia, reflecting local environmental contamination and also the geographical position of the country in South-East Europe. 相似文献
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In this short communication, we discuss European urban green space (UGS) research from an environmental justice perspective. We show that European UGS scholarship primarily focuses on functional values and managerial aspects of UGS, while paying less attention to equity in the enjoyment of and decision-making around UGS. On this basis we discuss potentials for European urban green space research to take up a more explicit environmental justice framing to shed much-needed light on injustices in European cities and inspire change in policy and practice. 相似文献
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Mirjam Milad Harald SchaichMatthias Bürgi Werner Konold 《Forest Ecology and Management》2011,261(4):829-843
With a predicted rise in average global surface temperature at an unprecedented rate, as well as changes in precipitation and disturbance regimes, climate change will bring forth new challenges for nature conservation in forest ecosystems. Species and habitats to be protected will be affected as well as related concepts and area specific objectives. Climate change impacts are likely to be aggravated by other anthropogenic stresses such as fragmentation, deposition or habitat destruction. To be reliable and effective, current objectives and guidelines of forest conservation need to be reassessed and improved. Our study analyses possible impacts of climate change on forests and identifies key future challenges for nature conservation in forests and ecosystem research. We reviewed 130 papers on climate change impacts on forest ecosystems and species published between 1995 and 2010. The geographical focus of the study is Central Europe. Papers were analysed accounting for direct and indirect impacts of gradual changes as well as stochastic disturbance events in forest ecosystems and their possible consequences for nature conservation.Even though broader aspects of nature conservation (protected areas, biodiversity) are frequently mentioned, little attention is given to forest-specific nature conservation. Particular aspects are insufficiently represented, such as the influence of climate change on different forest succession stages, the development of dead wood volume and quality, responses of secondary broadleaved species, azonal or extrazonal forests as well as ancient woodlands or remnants of historical silvicultural systems. Challenges arise in the context of great uncertainties about future developments. Nature conservation concepts and objectives in forests need to be adapted either within a permanent evaluation process or through the inclusion of further changes a priori, even if they are to some extent unpredictable. In some cases adaptation measures within nature conservation (e.g. adjusting protected areas) may conflict with interests of other stakeholders. Further research, particularly on interrelations between different impacts and the adaptive capacity of current forest ecosystems, associated species and existing genotypes is urgently needed. The scale and complexity of the task at hand calls for the establishment and further strengthening of international research networks. 相似文献
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Boris Ťupek Giuliana Zanchi Pieter J. Verkerk Galina Churkina Nicolas Viovy John K. Hughes Marcus Lindner 《Forest Ecology and Management》2010
The European forest carbon balance studied by various methods shows different results. We compared the regional and national net primary production (NPP) estimated by the forest inventory-based model EFISCEN and the climate-based terrestrial ecosystem models (TEMs: BIOME-BGC, ORCHIDEE, and JULES), and single forests NPP derived from the international network of eddy-covariance towers (FLUXNET). In addition, the paper presents the net ecosystem production (NEP) and the net biome production (NBP) calculated with EFISCEN and discusses the influence of forest management onto carbon fluxes. We aimed to better understand the variance between EFISCEN and TEMs NPP estimates, and to improve the assessment of European forest mitigation potential for the year 2005. 相似文献