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141.
142.
Christer G. Wiklund 《Behavioral ecology and sociobiology》1984,15(4):311-316
Summary In SW Sweden, solitary fieldfares (Turdus pilaris) were synchronized to the same degree as those living in colonies. In N Sweden, I investigated the degree of synchronization among colonies of varying size because solitary breeding occurred only occasionally. The degree of synchronization was not related to colony size. Synchronization was strongest in years when breeding started late and weakest in years when breeding commenced early. In N Sweden, the nest predation risk increased slightly as the season progressed. In SW Sweden, nestling mortality due to starvation was highest in early breeders, but their fledgling production exceeded that of late breeders. Increased nest predation penalized late layers. 相似文献
143.
Pirjola L Johansson C Kupiainen K Stojiljkovic A Karlsson H Hussein T 《Journal of the Air & Waste Management Association (1995)》2010,60(12):1422-1433
Very few real-world measurements of road dust suspension have been performed to date. This study compares two different techniques (referred to as Sniffer and Emma) to measure road dust emissions. The main differences between the systems are the construction of the inlet, different instruments for recording particulate matter (PM) levels, and different loads on the wheel axes (the weight of Sniffer was much higher than that of Emma). Both systems showed substantial small-scale variations of emission levels along the road, likely depending on-road surface conditions. The variations observed correlated quite well, and the discrepancies are likely a result of variations in dust load on the road surface perpendicular to the driving direction that cause variations in the measurements depending on slightly different paths driven by the two vehicles. Both systems showed a substantial influence on the emission levels depending on the type of tire used. The summer tire showed much lower suspension than the winter tires (one nonstudded and one studded). However, the relative importance of the nonstudded versus studded tire was rather different. For the ratio of studded/nonstudded, Emma shows higher values on all road sections compared with Sniffer. Both techniques showed increased emission levels with increasing vehicle speed. When the speed increased from 50 to 80 km hr(-1), the relative concentrations increased by 30-170% depending on the tire type and dust load. However, for road sections that were very dirty, Sniffer showed a much higher relative increase in the emission level with the nonstudded tire. Sniffer's absolute concentrations were mostly higher than Emma's. Possible reasons for the differences are discussed in the paper. Both systems can be used for studying relative road dust emissions and for designing air quality management strategies. 相似文献
144.
Basic principles and ecological consequences of changing water regimes: riparian plant communities 总被引:17,自引:1,他引:17
Recent research has emphasized the importance of riparian ecosystems as centers of biodiversity and links between terrestrial
and aquatic systems. Riparian ecosystems also belong among the environments that are most disturbed by humans and are in need
of restoration to maintain biodiversity and ecological integrity. To facilitate the completion of this task, researchers have
an important function to communicate their knowledge to policy-makers and managers. This article presents some fundamental
qualities of riparian systems, articulated as three basic principles. The basic principles proposed are: (1) The flow regime
determines the successional evolution of riparian plant communities and ecological processes. (2) The riparian corridor serves
as a pathway for redistribution of organic and inorganic material that influences plant communities along rivers. (3) The
riparian system is a transition zone between land and water ecosystems and is disproportionately plant species-rich when compared
to surrounding ecosystems. Translating these principles into management directives requires more information about how much
water a river needs and when and how, i.e., flow variables described by magnitude, frequency, timing, duration, and rate of
change. It also requires information about how various groups of organisms are affected by habitat fragmentation, especially
in terms of their dispersal. Finally, it requires information about how effects of hydrologic alterations vary between different
types of riparian systems and with the location within the watershed. 相似文献
145.
Adebayo A. Otitoloju Geraint B. Rogers Nicholas R. Bury Christer Hogstrand Kenneth D. Bruce 《The Environmentalist》2009,29(1):85-92
Bacterial strains were isolated from sediment samples from the Thames River. Successive transfer growth of the various strains
on nutrient agar containing increasing concentrations of AgNO3 revealed that three of the bacterial isolates were found to be capable of tolerating high concentrations of AgNO3 ranging from 20 to 80 mM on a solid medium and up to 10 mM AgNO3 in liquid medium. Molecular characterization and identification based on 16S rDNA gene sequencing of three strains of bacteria
that are tolerant to silver nitrate showed that the major tolerant strains include the superbug, Shewanella oneidensis, Pseudomonas sp. and Bacillus sp. Protein extraction and two-dimensional (2D) sodium dodecyl sulfate SDS-polyacrylamide gel electrophoresis (PAGE) of the
protein extracts in bacteria exposed to very high concentrations of AgNO3 revealed a general reduction in the number of expressed proteins, although two protein spots were conspicuously over expressed
in the exposed bacteria compared to control. The N-terminal amino acid sequence analysis of the protein spots identified the
major up-regulated proteins as the outer membrane protein To1C (45.2 kDa) and the structural protein of the flagellar filament,
flagellin (28.34 kDa), encoded for by the to1C and fliC genes, respectively. The roles of these genes in a number of multi-drug resistant pathogen and potentials for biotechnological
applications in toxic metal control for treatment of contaminated ecosystems and biomining were discussed. 相似文献
146.
Didac Pascual Jonas kerman Marina Becher Terry V. Callaghan Torben R. Christensen Ellen Dorrepaal Urban Emanuelsson Reiner Giesler Dan Hammarlund Edward Hanna Annika Hofgaard Hongxiao Jin Cecilia Johansson Christer Jonasson Jonatan Klaminder Jan Karlsson Erik Lundin Anders Michelsen David Olefeldt Andreas Persson Gareth K. Phoenix Zofia Rczkowska Riikka Rinnan Lena Strm Jing Tang Ruth K. Varner Philip Wookey Margareta Johansson 《Ambio》2021,50(2):375
Arctic and subarctic ecosystems are experiencing substantial changes in hydrology, vegetation, permafrost conditions, and carbon cycling, in response to climatic change and other anthropogenic drivers, and these changes are likely to continue over this century. The total magnitude of these changes results from multiple interactions among these drivers. Field measurements can address the overall responses to different changing drivers, but are less capable of quantifying the interactions among them. Currently, a comprehensive assessment of the drivers of ecosystem changes, and the magnitude of their direct and indirect impacts on subarctic ecosystems, is missing. The Torneträsk area, in the Swedish subarctic, has an unrivalled history of environmental observation over 100 years, and is one of the most studied sites in the Arctic. In this study, we summarize and rank the drivers of ecosystem change in the Torneträsk area, and propose research priorities identified, by expert assessment, to improve predictions of ecosystem changes. The research priorities identified include understanding impacts on ecosystems brought on by altered frequency and intensity of winter warming events, evapotranspiration rates, rainfall, duration of snow cover and lake-ice, changed soil moisture, and droughts. This case study can help us understand the ongoing ecosystem changes occurring in the Torneträsk area, and contribute to improve predictions of future ecosystem changes at a larger scale. This understanding will provide the basis for the future mitigation and adaptation plans needed in a changing climate.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01381-1) contains supplementary material, which is available to authorized users. 相似文献
147.