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41.
Voluntary exercise at the expense of reproductive success in Djungarian hamsters (Phodopus sungorus)
Energy demands of gestation and lactation represent a severe challenge for small mammals. Therefore, additional energetic
burdens may compromise successful breeding. In small rodents, food restriction, cold exposure (also in combination) and wheel
running to obtain food have been shown to diminish reproductive outcome. Although exhibited responses such as lower incidence
of pregnancy, extended lactation periods and maternal infanticide were species dependent, their common function is to adjust
energetic costs to the metabolic state reflecting the trade-off between maternal investment and self-maintenance. In the present
study, we sought to examine whether voluntary exercise affects reproduction in Djungarian hamsters (Phodopus sungorus), which are known for their high motivation to run in a wheel. Voluntary exercise resulted in two different effects on reproduction;
in addition to increased infanticide and cannibalism, which was evident across all experiments, the results of one experiment
provided evidence that free access to a running wheel may prevent successful pregnancy. It seems likely that the impact of
voluntary wheel running on reproduction was associated with a reduction of internal energy resources evoked by extensive exercise.
Since the hamsters were neither food-restricted nor forced to run in the present study, an energetic deficit as reason for
infanticide in exercising dams would emphasise the particularly high motivation to run in a wheel. 相似文献
42.
Ekholm P Jouttijärvi T Priha M Rita H Nurmesniemi H 《Environmental pollution (Barking, Essex : 1987)》2007,145(3):715-722
We determined the potentially algal-available P (P(aa)) in pulp and paper mill effluents by two bioassay techniques (a dual-culture assay and a batch approach) and compared it with chemically analysed P (total P, total dissolved P, reactive P, dissolved reactive P and dissolved hydrolysable P). The mean P(aa) given by the dual-culture assay was within a 40% range of that given by the batch approach. The P(aa) obtained by both bioassays differed from total P. Dissolved reactive P appeared to be the most readily available chemical P fraction, but other P fractions also contributed to P(aa). The analysis of reactive P, which involves direct staining of an unfiltered sample, best approximated the P(aa) given by the dual-culture assay (relative error 9%). The results suggest that assessment of eutrophying effluent P can be improved by analysing simple chemical P fractions in wastewater. The fractions to be analysed, however, may be site specific. 相似文献
43.
Water resources and land use are closely linked with each other and with regional climate, assembling a very complex system. The understanding of the interconnecting relations involved in this system is an essential step for elaborating public policies that can effectively lead to the sustainable use of water resources. In this study, an integrated modelling framework was assembled in order to investigate potential impacts of agricultural expansion and climate changes on Irrigation Water Requirements (IWR) in the Taita Hills, Kenya. The framework comprised a land use change simulation model, a reference evapotranspiration model and synthetic precipitation datasets generated through a Monte Carlo simulation. In order to generate plausible climate change scenarios, outputs from General Climate Models were used as reference to perturbing the Monte Carlo simulations. The results indicate that throughout the next 20 years the low availability of arable lands in the hills will drive agricultural expansion to areas with higher IWR in the foothills. If current trends persist, agricultural areas will occupy roughly 60% of the study area by 2030. This expansion will increase by approximately 40% the annual water volume necessary for irrigation. Climate change may slightly decrease crops' IWR in April and November by 2030, while in May a small increase will likely be observed. The integrated assessment of these environmental changes allowed a clear identification of priority regions for land use allocation policies and water resources management. 相似文献
44.
R. Räty L. Anttila A. Virtanen P. Koskinen P. Laitinen P. Mörsky A. Tiitinen H. Martikainen U. Ekblad 《黑龙江环境通报》2003,23(13):1045-1048
45.
Fluxes of methane,carbon dioxide and nitrous oxide in boreal lakes and potential anthropogenic effects on the aquatic greenhouse gas emissions 总被引:12,自引:0,他引:12
Huttunen JT Alm J Liikanen A Juutinen S Larmola T Hammar T Silvola J Martikainen PJ 《Chemosphere》2003,52(3):609-621
We have examined how some major catchment disturbances may affect the aquatic greenhouse gas fluxes in the boreal zone, using gas flux data from studies made in 1994-1999 in the pelagic regions of seven lakes and two reservoirs in Finland. The highest pelagic seasonal average methane (CH(4)) emissions were up to 12 mmol x m(-2) x d(-1) from eutrophied lakes with agricultural catchments. Nutrient loading increases autochthonous primary production in lakes, promoting oxygen consumption and anaerobic decomposition in the sediments and this can lead to increased CH(4) release from lakes to the atmosphere. The carbon dioxide (CO(2)) fluxes were higher from reservoirs and lakes whose catchment areas were rich in peatlands or managed forests, and from eutrophied lakes in comparison to oligotrophic and mesotrophic sites. However, all these sites were net sources of CO(2) to the atmosphere. The pelagic CH(4) emissions were generally lower than those from the littoral zone. The fluxes of nitrous oxide (N(2)O) were negligible in the pelagic regions, apparently due to low nitrate inputs and/or low nitrification activity. However, the littoral zone, acting as a buffer for leached nitrogen, did release N(2)O. Anthropogenic disturbances of boreal lakes, such as increasing eutrophication, can change the aquatic greenhouse gas balance, but also the gas exchange in the littoral zone should be included in any assessment of the overall effect. It seems that autochthonous and allochthonous carbon sources, which contribute to the CH(4) and CO(2) production in lakes, also have importance in the greenhouse gas emissions from reservoirs. 相似文献
46.
The paper describes and analyses the 100 year development of water supply and sanitation and the lessons learnt in Porvoo, a municipality of 46,000 people on the southern coast of Finland. In urban areas the municipality‐owned utility has always dominated. Over 90 per cent of the investments for the recent wastewater treatment plant went into services, equipment and goods bought from the private sector through 12 tenders, all based on competition. In the neighbouring rural areas, recently merged with the city, there are nine consumer‐managed, non‐profit water cooperatives that buy water in bulk from the city water utility. Although the solutions are based on local conditions and subsidiarity, some more general principles are also highlighted and discussed. Past decisions inevitably also affect future development options. 相似文献
47.
48.
Petri T. Niemel? Anssi Vainikka Sonja Lahdenper? Raine Kortet 《Behavioral ecology and sociobiology》2012,66(5):645-652
Population density regulates the strength of intraspecific competition and may thereby be reflected in life-history variables,
such as development time, growth rate, or investment in immune defense. However, population density may also affect the fitness
payoffs of different behaviors and consequently shape the development of personality. Here we studied if population density
during nymphal development (one, four, or ten individuals raised together) affects the level of boldness, measured as the
latency time to recover from freezing and emerge from a shelter, aggressiveness towards conspecifics or their correlation
at the adult stage in the field crickets, Gryllus integer. In addition, we tested if individuals invest more resources in immune function or speed up their development in response
to a high conspecifics density during ontogeny. Nymphal density did not affect adult boldness or aggressiveness towards conspecific
males per se, but these variables showed a negative association, i.e., indicated an unconventional behavioral syndrome in
the highest density treatment. Supporting the effectiveness of density treatments in inducing plastic responses, individuals
reached maturity sooner and invested more resources in immune function in the highest nymphal density group compared to groups
consisting of one or four individuals. Our results suggest that population density may play an important role in shaping both
the realized life history and development of behavioral syndromes. 相似文献
49.
Huttunen JT Alm J Saarijärvi E Lappalainen KM Silvola J Martikainen PJ 《Chemosphere》2003,50(2):247-250
The springtime methane (CH4) emission from a small, eutrophied boreal lake was assessed during the winter ice-cover by measurement of gas ebullition and CH4 accumulation in the water column in association with the development of oxygen depletion after ice formation. The winter CH4 production was estimated to result in a loss of 3.6-7.9 g CH4 m(-2) from the lake to the atmosphere during the short period of ice melt. This could account for 22-48% of the annual CH4 emission from the pelagic zone of the lake. The contribution of winter to the annual CH4 release can be similar or even higher in seasonally ice-covered northern aquatic ecosystems than in northern terrestrial wetlands, thus winter must be considered in any studies into the aquatic CH4 emissions. The trophic state and wintertime oxygen conditions, linked to the changes in land-use in the catchments and climate, are important factors controlling the springtime lake CH4 emissions. 相似文献
50.
There is a frequent need in the environmental sciences to show the similarity of the results given by two analytical methods. This cannot, however, be done within the conventional 'there is a difference' statistical hypothesis setting of, among others, Student's t-test. We demonstrate here a more appropriate approach that originates from drug testing and that can be applied with standard statistical software. It is a challenging approach, as it requires quantification of the similarity limit. If no pre-determined value is given for similarity, a potential data-supported similarity limit can be explored from the data. The approach has numerous other potential application areas, e.g. parallelism of regression slopes, homogeneity of variances and lack of interaction. 相似文献