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排序方式: 共有128条查询结果,搜索用时 15 毫秒
21.
退化羊草草地生态恢复过程中大型土壤动物群落生态特征 总被引:1,自引:0,他引:1
选取吉林省大安市姜家甸草场天然羊草草地、一年生人工碱茅草地和一年生人工碱茅草地为研究样地,于2002与2003年7月份两次对样地进行野外采样。共捕获大型土壤动物3130只,分别隶属2门5纲10目13类。通过对比研究表明:土壤动物群落间个体密度有一定的差异,鞘翅同在各生境中都有较高个体密度分布,显示其是该草原地带大型土壤动物的特征性类群,土壤动物类群和个体数垂直分布表聚程度群落间有较大不同,土壤动物群落生物多样性存在空间分异。认为水肥干预可以增加土壤动物群落的生物多样性。DG多样性指数更适合表达不同演替阶段土壤动物群落的差异,大型土壤动物群落生物多样性能够指示退化草地生态系统恢复与重建过程。 相似文献
22.
Urban Kjellén 《Safety Science》2012,50(10):1941-1951
International companies investing in emerging markets need to address the management of safety under varying conditions. The paper presents an evaluation of the approaches taken by an international hydropower company in two different construction projects, one in India and one in the Philippines. In the first project, the company had to intervene as a reaction to poor safety and overall performance. Based on previous experiences, the company selected a proactive approach in the second project, involving use of the contracting process to ensure adequate conditions from the start of construction and onwards. The paper accounts for the safety performance results in the two projects and interprets them in relationship to external and internal influencing factors in the respective project. It is concluded that a proactive approach has the potential of delivering satisfactory safety results at moderate costs for follow-up. A reactive approach risks exposing the company to ethical and reputation risks due to a poor safety performance before the corrective actions have taken full effect. It is also resource demanding. Results demonstrate the feasibility of turning around a project’s safety performance also when preconditions are challenging. 相似文献
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In Germany automobile exhaust control by platinum-group element (PGE) loaded catalysts is now well established. By mechanical or chemical attrition, these catalysts could act as a potential source for a significant increase of PGE abundances in the environment. During a recent research program concentrations and distributions of PGE in different soils were measured along the highway A66 Frankfurt-Wiesbaden. 71 nearsurface soil samples were analysed by graphite furnace atomic absorption spectrometry (GFAAS). The results revealed average abundances of 10 ppb platinum and 3 ppb ruthenium. Palladium as well as rhodium were below the analytical detection limit of 2 ppb. With increasing distance from the highway edge PGE values gradually decreased. Only the upmost soil layer, down to 20 cm depth, contains measurable PGE concentrations. Results: There are irregular PGE concentrations of anthropogenic origin in different soils along the highway A66 Frankfurt-Wiesbaden possibly arising from automobile exhaust catalysts. Further monitoring could help to avoid potential environmental hazards. *** DIRECT SUPPORT *** A00HP020 00002 相似文献
25.
Luděk Bartoš Jitka Bartošová Jan Pluháček Jana Šindelářová 《Behavioral ecology and sociobiology》2011,65(8):1567-1572
Based on questionnaires from horse breeders, we found that bringing a pregnant mare which had been mated away from home into
a vicinity of a familiar male who was not the father of her foetus increased probability of pregnancy disruption. These mares
aborted in 31% of cases, while none of those mated within the home stable aborted. Repeated sexual activity either by a stallion
or dominant gelding from the normal home group was observed shortly after the mare came from away-mating. Pregnant mares isolated
from home males by a fence were even seen soliciting them over the fence. We speculate that, once returned to the home “herd”,
and introduced to familiar males, mares were more likely to terminate their pregnancy to save energy and avoid likely future
infanticidal loss of their progeny by dominant male(s) of the home social group. This is a newly discovered phenomenon where
a mare manipulates the male’s paternity assessment by promiscuous mating. It may explain a common increased incidence of foetal
loss in domestic horses occurring in nearly 40% of pregnancies. We conclude that the common practice of transporting the mare
for mating and then bringing her back to an environment with males, stallions or geldings, which did not sire the foetus,
is the main cause of high percentages of pregnancy disruption in domestic horses. 相似文献
26.
Aerosol concentration and particle size distributions in underground excavations of a hard coal mine
Krystian Skubacz Łukasz Wojtecki Paweł Urban 《International journal of occupational safety and ergonomics》2013,19(3):318-327
Deposition of aerosols in the respiratory system depends inter alia on their size and the respiratory tract deposition is appreciable for nanometer-sized particles. This article presents the results of measurements of size distributions of aerosols in the range of several nanometers up to about 20?μm in the underground mine excavations of an active hard coal mine. The study included practically all particles of a respirable fraction. The results showed that a high concentration of fine and ultrafine aerosols occurs in key underground workplaces especially during mining machine operations, although their contribution to total mass concentration is usually negligible. 相似文献
27.
Klára Řehounková Lukáš Čížek Jiří Řehounek Lenka Šebelíková Robert Tropek Kamila Lencová Petr Bogusch Pavel Marhoul Jan Máca 《Environmental science and pollution research international》2016,23(14):13745-13753
Open interior sands represent a highly threatened habitat in Europe. In recent times, their associated organisms have often found secondary refuges outside their natural habitats, mainly in sand pits. We investigated the effects of different restoration approaches, i.e. spontaneous succession without additional disturbances, spontaneous succession with additional disturbances caused by recreational activities, and forestry reclamation, on the diversity and conservation values of spiders, beetles, flies, bees and wasps, orthopterans and vascular plants in a large sand pit in the Czech Republic, Central Europe. Out of 406 species recorded in total, 112 were classified as open sand specialists and 71 as threatened. The sites restored through spontaneous succession with additional disturbances hosted the largest proportion of open sand specialists and threatened species. The forestry reclamations, in contrast, hosted few such species. The sites with spontaneous succession without disturbances represent a transition between these two approaches. While restoration through spontaneous succession favours biodiversity in contrast to forestry reclamation, additional disturbances are necessary to maintain early successional habitats essential for threatened species and open sand specialists. Therefore, recreational activities seem to be an economically efficient restoration tool that will also benefit biodiversity in sand pits. 相似文献
28.
Varying rotation lengths in northern production forests: Implications for habitats provided by retention and production trees 总被引:1,自引:0,他引:1
Adam Felton Johan Sonesson Urban Nilsson Tomas Lämås Tomas Lundmark Annika Nordin Thomas Ranius Jean-Michel Roberge 《Ambio》2017,46(3):324-334
Because of the limited spatial extent and comprehensiveness of protected areas, an increasing emphasis is being placed on conserving habitats which promote biodiversity within production forest. For this reason, alternative silvicultural programs need to be evaluated with respect to their implications for forest biodiversity, especially if these programs are likely to be adopted. Here we simulated the effect of varied rotation length and associated thinning regimes on habitat availability in Scots pine and Norway spruce production forests, with high and low productivity. Shorter rotation lengths reduced the contribution made by production trees (trees grown for industrial use) to the availability of key habitat features, while concurrently increasing the contribution from retention trees. The contribution of production trees to habitat features was larger for high productivity sites, than for low productivity sites. We conclude that shortened rotation lengths result in losses of the availability of habitat features that are key for biodiversity conservation and that increased retention practices may only partially compensate for this. Ensuring that conservation efforts better reflect the inherent variation in stand rotation lengths would help improve the maintenance of key forest habitats in production forests. 相似文献
29.
Anna Francová Vladislav Chrastný Hana Šillerová Jana Kocourková Michael Komárek 《Environmental monitoring and assessment》2017,189(9):478
This study is a continuation of our preceding research identifying suitable environmental samples for the tracing of atmospheric pollution in industrial areas. Three additional types of environmental samples were used to characterise contamination sources in the industrial area of Ostrava city, Czech Republic. The region is known for its extensive metallurgical and mining activities. Fingerprinting of stable Pb isotopes was applied to distinguish individual sources of anthropogenic Pb. A wide range of 206Pb/207Pb ratios was observed in the investigated samples: 206Pb/207Pb = 1.168–1.198 in mosses; 206Pb/207Pb = 1.167–1.215 in soils and 206Pb/207Pb = 1.158–1.184 in tree cores. Black and brown coal combustion, as well as metallurgical activities, is the two main sources of pollution in the area. Fossil fuel burning in industry and households seems to be a stronger source of Pb emissions than from the metallurgical industry. Concentration analyses of tree rings showed that a significant increase in As concentrations occurred between 1999 and 2016 (from 0.38 mg kg?1 to 13.8 mg kg?1). This shift corresponds to the use of brown coal from Bílina, Czech Republic, with an increased As concentration. The burning of low-quality fuels in households remains a problem in the area, as small ground sources have a greater influence on the air quality than do industrial sources. 相似文献
30.