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221.
As a result of forcing the energy utilization from biomass, the amounts of combustion residues, especially woodash, are growing. For a sustainable and ecologically effective closed-cycle economy, the knowledge of the chemical composition of the ashes is necessary. The matrix wood ash is very complex, due to the great number of constituents in different concentrations. Therefore it is important to develop a combination of analytical methods for the complete detection of nutrients and heavy metals in wood ash. Ashes from different heating plants (wood chips-, bark-and sawdust combustion systems) were analysed with X-ray methods as well as with acid-digestion in combination with atomic spectrometry detection. The results were compared and checked for their plausibility by statistical methods and material balances for the inorganic elements from the biomass to the ash fractions. As a result of this evaluation astandard method is recommended for the analysis of wood ash. This method consists of a combination of dry (X-ray) analysis (for the elements Si, Ca, Mg, K, P, Al, Fe, Mn) and fluid analysis (for the detection of heavy metals). 相似文献
222.
NO production and the rate constant of NO consumptionin soil samples from Amazonian forest and pasturesites were determined in the laboratory. The purposewas to study NO production and consumption in soilsfrom both types of land use as functions of soiltemperature and soil moisture. NO productionincreased exponentially with soil temperature. Thedegree of increase depended on soil moisture,indicating that the response of NO production to achange in soil temperature is most pronounced at acertain intermediate soil moisture. NO productionpeaked at a soil moisture of 0.10 g g-1, correspondingto 0.27 and 0.38 water-filled pore space for forestand pasture soils, respectively. The optimum soilmoisture for which maximum NO release was observedwas independent of soil temperature. NO consumptionwas most efficient at high soil temperatures andunder dry soil conditions. NO release wasapproximately 10 times larger for forest than pasturesoil. The difference may be related to the higherNO3
- content in forest soil. 相似文献
223.
Heiko Schmaljohann Martin Buchmann James W. Fox Franz Bairlein 《Behavioral ecology and sociobiology》2012,66(6):915-922
Movement ecology studies have highlighted the importance of individual-based research. As tracking devices have not been applicable for identifying year-around movements of small birds until recently, migration routes of such species relied on visual observations and ring recoveries. Within the Palaearctic–African migration system, loop migration seems to be the overall migration pattern. The interindividual variations within species-specific migration routes are, however, unknown. Here, we track the individual migration routes and annual cycles of male Northern Wheatears Oenanthe oenanthe, a trans-Sahara songbird migrant from a German breeding population with light-level geolocators. Two migrated most likely via Spain towards western Africa but returned via Corsica/Sardinia, while two others seemed to migrate via Sardinia and Corsica in autumn and via Spain and France in spring (loop migration). The fifth took presumably the same route via France and the Balearics in both seasons. All birds wintered in the Sahel zone of western Africa. Overall migration distances for autumn and spring were similar (about 4,100?km), whereas the overall migratory speed was generally higher in spring (126?km?day?1) than in autumn (88?km?day?1). Birds spent about 130?days at the breeding area and 147?days at the wintering grounds. 相似文献
224.
A simulation model was developed to investigate the relative effects of temperature, oxygen concentration, substrate content and competition by autochthonous microbial community on the oscillatory behaviour and survival of Escherichia coli O157:H7 in manure and manure-amended soil. The overall decline in E. coli O157:H7 was primarily determined by competition with autochthonous copiotrophic bacteria simulated by an inter-specific competition term according to Lotka-Volterra. Oscillations of bacterial populations were attained by the relationships between relative growth and death rates with readily available substrate content. The model contains a logistic and exponential relation of relative growth and death rates, respectively, of E. coli O157:H7 and copiotrophic bacteria with temperature, resulting in optimum curves for net growth rates similar to the curves reported in the literature. The model has been both calibrated and validated on experimental data. The model was used to perform sensitivity analysis and to evaluate different manure and soil management scenarios in terms of survival of E. coli O157:H7. The relative effects of changes in temperature on simulated survival time of E. coli O157:H7 were more pronounced than changes in oxygen condition. Testing manure storage scenarios with realistic data revealed that manure stored in a heap that was turned every week resulted in almost 70% reduction of E. coli O157:H7 survival compared to unturned manure. At the surface of a heap with unturned manure, simulated survival time was the longest (2.4 times longer than inside the same heap). The simulation model provides a new approach to investigating dynamic changes of invasive microorganisms in natural substrates such as manure or manure-amended soil. 相似文献
225.
Resource competition theory predicts that, in equilibrium, the number of coexisting species cannot exceed the number of limiting resources. In some competition models, however, competitive interactions may result in nonequilibrium dynamics, allowing the coexistence of many species on few resources. The relevance of these findings is still unclear, since some assumptions of the underlying models are unrealistic. Most importantly, these models assume that individual growth directly reflects the availability of external resources, whereas real organisms can store resources, thereby decoupling their growth from external fluctuations. Here we study the effects of resource storage by extending the well-known Droop model to the context of multiple species and multiple resources. We demonstrate that the extended Droop model shows virtually the same complex dynamics as models without storage. Depending on the model parameters, one may obtain competitive exclusion, stable equilibrium coexistence, periodic and non-periodic oscillations, and chaos. Again, nonequilibrium dynamics allows for the coexistence of many species on few resources. We discuss our findings in the light of earlier work on resource competition, highlighting the role of luxury consumption, trade-offs in competitive abilities, and ecological stoichiometry. 相似文献
226.
Julia Delingat Franz Bairlein Anders Hedenström 《Behavioral ecology and sociobiology》2008,62(7):1069-1078
Behaviour on migration was often suggested to be selected for time-minimising strategies. Current optimality models predict
that optimal fuel loads at departure from stopover sites should increase with increasing fuel deposition rates. We modified
such models for the special case of the east Atlantic crossing of the Northern Wheatear (Oenanthe oenanthe). From optimality theory, we predict that optimal time-minimising behaviour in front of such a barrier should result in a
positive correlation between fuel deposition rates and departure fuel loads only above a certain threshold, which is the minimum
fuel load (f
min) required for the barrier crossing. Using a robust range equation, we calculated the minimum fuel loads for different barrier
crossings and predict that time-minimising wheatears should deposit a minimum of 24% fuel in relation to lean body mass (m
0
) for the sea crossing between Iceland and Scotland. Fuel loads of departing birds in autumn in Iceland reached this value
only marginally but showed positive correlation between fuel deposition rate (FDR) and departure fuel load (DFL). Birds at
Fair Isle (Scotland) in spring, which were heading towards Iceland or Greenland, were significantly heavier and even showed
signs of overloading with fuel loads up to 50% of lean body mass. Departure decisions of Icelandic birds correlated significantly
with favourable wind situations when assuming a migration direction towards Spain; however, the low departure fuel loads contradict
a direct non-stop flight. 相似文献
227.
Seasonal ice cover creates a pool of cold bottom water on the eastern Bering Sea continental shelf each winter. The southern edge of this cold pool, which defines the ecotone between arctic and subarctic communities, has retreated approximately 230 km northward since the early 1980s. Bottom trawl surveys of fish and invertebrates in the southeastern Bering Sea (1982-2006) show a coincident reorganization in community composition by latitude. Survey catches show community-wide northward distribution shifts, and the area formerly covered by the cold pool has seen increases in total biomass, species richness, and average trophic level as subarctic fauna have colonized newly favorable habitats. Warming climate has immediate management implications, as 57% of variability in commercial snow crab (Chionoecetes opilio) catch is explained by winter sea ice extent. Several measures of community distribution and structure show linear relationships with bottom temperature, suggesting warming climate as the primary cause of changing biogeography. However, residual variability in distribution not explained by climate shows a strong temporal trend, suggesting that internal community dynamics also contribute to changing biogeography. Variability among taxa in their response to temperature was not explained by commercial status or life history traits, suggesting that species-specific responses to future warming will be difficult to predict. 相似文献
228.
229.
Speciation—the origin of new species—is the source of the diversity of life. A theory of speciation is essential to link poorly
understood macro-evolutionary processes, such as the origin of biodiversity and adaptive radiation, to well understood micro-evolutionary
processes, such as allele frequency change due to natural or sexual selection. An important question is whether, and to what
extent, the process of speciation is ‘adaptive’, i.e., driven by natural and/or sexual selection. Here, we discuss two main
modelling approaches in adaptive speciation theory. Ecological models of speciation focus on the evolution of ecological differentiation
through divergent natural selection. These models can explain the stable coexistence of the resulting daughter species in
the face of interspecific competition, but they are often vague about the evolution of reproductive isolation. Most sexual
selection models of speciation focus on the diversification of mating strategies through divergent sexual selection. These
models can explain the evolution of prezygotic reproductive isolation, but they are typically vague on questions like ecological
coexistence. By means of an integrated model, incorporating both ecological interactions and sexual selection, we demonstrate
that disruptive selection on both ecological and mating strategies is necessary, but not sufficient, for speciation to occur.
To achieve speciation, mating must at least partly reflect ecological characteristics. The interaction of natural and sexual
selection is also pivotal in a model where sexual selection facilitates ecological speciation even in the absence of diverging
female preferences. In view of these results, it is counterproductive to consider ecological and sexual selection models as
contrasting and incompatible views on speciation, one being dominant over the other. Instead, an integrative perspective is
needed to achieve a thorough and coherent understanding of adaptive speciation. 相似文献
230.
On the choice of farm management practices after the reform of the Common Agricultural Policy in 2003 总被引:1,自引:0,他引:1
The Common Agricultural Policy (CAP) was fundamentally reformed in 2003. From 2005, farmers will receive decoupled income support payments instead of production premiums if basic standards for environment, food safety, animal health and welfare are met. Farmers are likely to adjust production and management practices to the new policy framework. We describe how this reform fits into the EU strategy of making agricultural production more environmentally friendly by concentrating on the financial aspects of the reforms. Using an agricultural sector model for Austria, we show that the reform will further decrease agricultural outputs, reduce farm inputs, lessen nitrogen surpluses and make environmentally friendly management practices more attractive for farmers. 相似文献