75 Jahre Theorie des expandierenden Kosmos: Friedmann Modelle und der “Einstein–Limit”

  Die geschichtliche Entwicklung der kosmologischen Modelle für den homogen–isotropen Kosmos, beginnend mit Alexander Friedmanns epochalen Arbeiten (1922 und 1924) bis zur heutigen Diskussion aktueller Modelle wird dargestellt. Eine kardinale Rolle spielt die offene Frage: Besteht die Materie des Kosmos zum weit überwiegenden Teil aus nicht–baryonischer (sog. exotischer) Dunkel–Materie oder reicht die gesamte baryonische Materie aus, die aus den bekannten Atomen und Molekülen besteht, um die Entwicklung des Kosmos zu verstehen. Auch von der normalen (baryonischen) Materie im Kosmos ist nur ein geringer Anteil (etwa 20 5 Prozent) in leuchtenden Objekten (Sterne, Gas, Staub) direkt beobachtbar. Im Abschnitt 3 wird der “Einstein–Limit” für die kosmologische Konstante erl?utert und eine leicht einsichtige Herleitung des Zahlenwertes gegeben.     

Seasonal occurrence of the ctenophore Pleurobrachia pileus in the western Dutch Wadden Sea

Due to the short residence time of the water in the western Dutch Wadden Sea the ctenophore Pleurobrachia pileus has to be considered as an allochthonous species, which enters the estuary passively from the North Sea. The seasonal occurrence of this species in the Dutch Wadden Sea is a reflection of its abundance in the coatal zone of the North Sea and is characterized by a pronounced spring peak of up to 17000 individuals per 1000 m³ and a lower autumn peak with numbers up to 400 individuals per 1000 m³. Similar to other areas, predation by Beroë gracilis, another ctenophore species, may be a factor in controlling the P. pileus population in this region, although B. gracilis abundance is low. P. pileus is only important as a predator for a short time, i.e. the month of May, when it reaches maximum biomass values of up to 12 00 mgC per 1000 m³. Both the estimated potential consumption rates in comparison with the available food as well as the observed suboptimal growth rate of the population suggest that in the coastal zone of the North Sea area food conditions may not be optimal for P. pileus.     

The Dutch National System for forest sector greenhouse gas reporting under UNFCCC

A full account for carbon dioxide (CO₂) and other greenhouse gas balance is presented for the Dutch forest and nature areas for 1990–2002 at a Tier 2.5 level. The paper outlines how complex guidelines can be turned into a practical system, appropriate for a small country, making use of the best knowledge and data available. The net total sink of all processes of the forest and other nature terrains balance is very stable through time around an average of 1.74 million tonnes of CO₂ per year. The sink is to a large extent determined by the growth of forest remaining forest, and the harvest taking place in there. Newly added processes in this new National System are significant as well, but they compensate each other. The sources from deforestation and nitrous oxide (N₂O) emissions (around 900 ktonne CO₂) are for two thirds compensated by the sinks from afforestation, dead wood, soil C changes due to land use changes, and trees outside the forest. The land use changes between 1990 and 2000 showed that The Netherlands has an annual deforestation of 2504 ha (0.7% of the forest area) and an afforestation of 3124 ha. Deforestation led in total over the 13 years of 1990–2002 to an emission of 11.2 million tonne CO₂ compensated by only 1.9 million tonne CO₂ due to afforestation.

Lessons learnt from a participatory integrated assessment of greenhouse gas emission reduction options in firms

This article discusses an approach for identification and evaluation of short-term greenhouse gas (GHG) emission reduction options in firms. The approach is based on lessons learnt from a project using Participatory Integrated Assessment (PIA) and builds on the idea that effective public climate policy for firms requires options that have support from stakeholders and are practically feasible. Scenarios are used to provide a link with short-term policy developments and a model assists to communicate quantitative effects of options to participating stakeholders. Our approach can be seen as a first step towards a framework that meets the need for more systematic approaches to PIAs identifying effective public policies for short-term GHG emission reduction options in firms. In order to identify effective options for non-carbon dioxide GHG emission reductions, our approach has been applied to Dutch dairy farms, after which it has been refined. The case study suggests that our approach can provide balance between practical, context specific issues and scientific-theoretical aspects, thereby avoiding common pitfalls of participatory research projects to focus too much on either theory or practical issues.

The toxicity of copper contaminated soil using a gnotobiotic Soil Multi-species Test System (SMS)

A gnotobiotic multi-species study was designed to consist of a food-web of soil-dwelling animals. The food-web was exposed to five concentrations copper (Cu) spiked soil for three exposure durations i.e. 28, 56 and 84 days. Based on multivariate analysis the food-web was significantly affected by Cu exposure at and above 300 mg Cu kg(-1) soil (lowest tested concentration). The number of animals present in the 2500 mg Cu kg(-1) (highest tested concentration) was at all sampling occasions below the starting point level. Based on analysis of the individual species the lowest 10% effect concentration (EC10) observed was 50 mg Cu kg(-1) soil, for Enchytraeus crypticus. Using the EC10 for the individual species the HC5 (Hazard Concentration at the 5% level) was estimated to be between 25 and 36 mg Cu kg(-1) soil, depending on the exposure duration. A similar experiment but using a reduced design was performed employing soil contaminated with Cu in the field more than 80 years ago. The trend in the field-contaminated soil was similar to that observed for the spiked soil.     

Mate guarding and territorial aggression vary with breeding synchrony in golden whistlers (<Emphasis Type="Italic">Pachycephala pectoralis</Emphasis>)

Male paternity assurance behaviour during the female fertile period has been widely documented amongst birds. In contrast, how sex-specific behavioural strategies vary with local breeding synchrony levels remains largely unknown. This is important because, in many species, intra-population patterns of extra-pair fertilisation rates, and hence cuckoldry risk, are known to vary with the number of simultaneously fertile females. Each sex may therefore differ in how they behave towards male conspecifics during different degrees of breeding synchrony. Here I provide evidence of such sex-specific differences in the golden whistler (Pachycephala pectoralis), a species in which within-pair paternity assurance is negatively associated with breeding synchrony. Via simulated territorial intrusions using decoy males, I show that males, but not females, increase levels of aggression to male intruders during periods of low synchrony, possibly because cuckoldry risk is greatest during this period. In addition, males appear to invest more effort into mate guarding after, but not before, territorial intrusions during this period. These inter-sexual differences may reflect conflicts in interest between the sexes, with females consistently showing interest in males during the fertile period regardless of synchrony levels and males investing more resources into expelling intruders when the risk of paternity loss is greatest. This study thus provides evidence that males may be able to detect variation in breeding synchrony and cuckoldry risk and adjust their paternity assurance behaviour accordingly.     

Comparison of two reactor concepts for anoxygenic H2 production by Rhodobacter capsulatus

In the contribution at hand two main concepts of photobioreactors are considered: the flat-panel reactor and the tubular reactor. Both reactors are investigated under outdoor conditions in Germany in the summer time for their applicability for H₂ production by means of purple non-sulphur bacteria Rhodobacter capsulatus. The experiments are performed as fed batch. The performance of a photobioreactor is evaluated in terms of H₂ productivity per IRS (illuminated reactor surface). It is demonstrated that both reactors could be operated stable for several weeks with comparable H₂ productivities. The mean hydrogen productivity for the panel and the tubular reactor is 3690 ml H₂/(m_IRS² d) and 3350 ml H₂/(m_IRS² d) respectively. While approximately 8 m² of the illuminated reactor surface of the panel reactor can be installed on 1 m² of ground space, the relation of the illuminated reactor surface to the ground area for the tubular reactor is approximately 1–1.     

Bayesian calibration of the nitrous oxide emission module of an agro-ecosystem model

Nitrous oxide (N₂O) is the main biogenic greenhouse gas contributing to the global warming potential (GWP) of agro-ecosystems. Evaluating the impact of agriculture on climate therefore requires a capacity to predict N₂O emissions in relation to environmental conditions and crop management. Biophysical models simulating the dynamics of carbon and nitrogen in agro-ecosystems have a unique potential to explore these relationships, but are fraught with high uncertainties in their parameters due to their variations over time and space. Here, we used a Bayesian approach to calibrate the parameters of the N₂O submodel of the agro-ecosystem model CERES-EGC. The submodel simulates N₂O emissions from the nitrification and denitrification processes, which are modelled as the product of a potential rate with three dimensionless factors related to soil water content, nitrogen content and temperature. These equations involve a total set of 15 parameters, four of which are site-specific and should be measured on site, while the other 11 are considered global, i.e. invariant over time and space. We first gathered prior information on the model parameters based on the literature review, and assigned them uniform probability distributions. A Bayesian method based on the Metropolis–Hastings algorithm was subsequently developed to update the parameter distributions against a database of seven different field-sites in France. Three parallel Markov chains were run to ensure a convergence of the algorithm. This site-specific calibration significantly reduced the spread in parameter distribution, and the uncertainty in the N₂O simulations. The model’s root mean square error (RMSE) was also abated by 73% across the field sites compared to the prior parameterization. The Bayesian calibration was subsequently applied simultaneously to all data sets, to obtain better global estimates for the parameters initially deemed universal. This made it possible to reduce the RMSE by 33% on average, compared to the uncalibrated model. These global parameter values may be used to obtain more realistic estimates of N₂O emissions from arable soils at regional or continental scales.