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Regional Environmental Change - Mediterranean forests are found in the Mediterranean basin, California, the South African Cape Province, South and southwestern Australia and parts of Central Chile....  相似文献   
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Uptake of 137Cs was measured in different agricultural plant species (beans, lettuce, barley and ryegrass) grown in 5 undisturbed soil monoliths covering major European soil types. The first cultivation was made three years after soil contamination and plants were grown during 3 successive years. The plant–soil 137Cs transfer factors varied maximally 12-fold among soils and 35-fold among species when grown on the same soil. Single correlations between transfer factors and soil properties were found, but they varied widely with plant type and can hardly be used as a predictive tool because of the few soils used. The variation of 137Cs concentrations in plants among soils was related to differences in soil solution 137Cs and K concentrations, consistent with previous observations in hydroponics and pot trials. Absolute values of transfer factors could not be predicted based on a model validated for pot trials. The 137Cs activity concentration in soil solution decreased significantly (11- to 250-fold) for most soils in the 1997–1999 period and is partly explained by decreasing K in soil solution. Transfer factors of lettuce showed both increasing and decreasing trends between 2 consecutive years depending on soil type. The trends could be explained by the variation in 137Cs and K concentrations in soil solution. It is concluded that differences in 137Cs transfer factors among soils and trends in transfer factors as a function of time can be explained from soil solution composition, as shown previously for pot trials, although absolute values of transfer factors could not be predicted.  相似文献   
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Various counting rules are used for spore trap analysis. Partial count can lead to concentration errors. This paper demonstrates that the number of traverses counted affects the final results.  相似文献   
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During unpredictable adverse conditions, endotherms can engage in emergency behaviors (movement, torpor, hyperphagia) to maintain energy balance and reduce mortality hazards. Bird “escape migration” is one of the most visible of these behaviors. In this study, we focus on a Eurasian Woodcock Scolopax rusticola population. Seasonal migrations bring this population from its breeding grounds in Eastern and Northern Europe to its wintering grounds in France. A varying number of these birds are also regularly reported from Spain, supposedly during additional escape movements that occur in winter. Using models that account for the imperfect detection rate of individuals and a large (>44,000 individuals) dataset combining information from the wintering and breeding ranges, we show that severe winters significantly reduced survival probability, but that migration to Spain increased only during the most intense cold spell that occurred over the 20-year study period. This suggests that the decision to resume migration during the winter is submitted to a threshold mechanism, which we discuss in the light of current models of migratory behavior.  相似文献   
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Emissions from land transport, and from road transport in particular, have significant impacts on the atmosphere and on climate change. This assessment gives an overview of past, present and future emissions from land transport, of their impacts on the atmospheric composition and air quality, on human health and climate change and on options for mitigation.In the past vehicle exhaust emission control has successfully reduced emissions of nitrogen oxides, carbon monoxide, volatile organic compounds and particulate matter. This contributed to improved air quality and reduced health impacts in industrialised countries. In developing countries however, pollutant emissions have been growing strongly, adversely affecting many populations. In addition, ozone and particulate matter change the radiative balance and hence contribute to global warming on shorter time scales. Latest knowledge on the magnitude of land transport's impact on global warming is reviewed here.In the future, road transport's emissions of these pollutants are expected to stagnate and then decrease globally. This will then help to improve the air quality notably in developing countries. On the contrary, emissions of carbon dioxide and of halocarbons from mobile air conditioners have been globally increasing and are further expected to grow. Consequently, road transport's impact on climate is gaining in importance. The expected efficiency improvements of vehicles and the introduction of biofuels will not be sufficient to offset the expected strong growth in both, passenger and freight transportation. Technical measures could offer a significant reduction potential, but strong interventions would be needed as markets do not initiate the necessary changes. Further reductions would need a resolute expansion of low-carbon fuels, a tripling of vehicle fuel efficiency and a stagnation in absolute transport volumes. Land transport will remain a key sector in climate change mitigation during the next decades.  相似文献   
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