Operational flood management under large-scale extreme conditions, using the example of the Middle Elbe

In addition to precautionary or technical flood protection measures, short-term strategies of the operational management, i.e. the initiation and co-ordination of preventive measures during and/or before a flood event are crucially for the reduction of the flood damages. This applies especially for extreme flood events. These events are rare, but may cause a protection measure to be overtopped or even to fail and be destroyed. In such extreme cases, reliable decisions must be made and emergency measures need to be carried out to prevent even larger damages from occurring. <br><br> Based on improved methods for meteorological and hydrological modelling a range of (physically based) extreme flood scenarios can be derived from historical events by modification of air temperature and humidity, shifting of weather fields and recombination of flood relevant event characteristics. By coupling the large scale models with hydraulic and geotechnical models, the whole flood-process-chain can be analysed right down to the local scale. With the developed GIS-based tools for hydraulic modelling <i>FlowGIS</i> and the Dike-Information-System, (IS-dikes) it is possible to quantify the endangering shortly before or even during a flood event, so the decision makers can evaluate possible options for action in operational mode

Inconsistent impacts of decomposer diversity on the stability of aboveground and belowground ecosystem functions

The intensive discussion on the importance of biodiversity for the stability of essential processes in ecosystems has prompted a multitude of studies since the middle of the last century. Nevertheless, research has been extremely biased by focusing on the producer level, while studies on the impacts of decomposer diversity on the stability of ecosystem functions are lacking. Here, we investigate the impacts of decomposer diversity on the stability (reliability) of three important aboveground and belowground ecosystem functions: primary productivity (shoot and root biomass), litter decomposition, and herbivore infestation. For this, we analyzed the results of three laboratory experiments manipulating decomposer diversity (1–3 species) in comparison to decomposer-free treatments in terms of variability of the measured variables. Decomposer diversity often significantly but inconsistently affected the stability of all aboveground and belowground ecosystem functions investigated in the present study. While primary productivity was mainly destabilized, litter decomposition and aphid infestation were essentially stabilized by increasing decomposer diversity. However, impacts of decomposer diversity varied between plant community and fertility treatments. There was no general effect of the presence of decomposers on stability and no trend toward weaker effects in fertilized communities and legume communities. This indicates that impacts of decomposers are based on more than effects on nutrient availability. Although inconsistent impacts complicate the estimation of consequences of belowground diversity loss, underpinning mechanisms of the observed patterns are discussed. Impacts of decomposer diversity on the stability of essential ecosystem functions differed between plant communities of varying composition and fertility, implicating that human-induced changes of biodiversity and land-use management might have unpredictable effects on the processes mankind relies on. This study therefore points to the necessity of also considering soil feedback mechanisms in order to gain a comprehensive and holistic understanding of the impacts of current global change phenomena on the stability of essential ecosystem functions

Micellization of Model Macromolecular Surfactants as Studied by Static Light Scattering

cited By 12International audienceMicellization of ionically end-capped polystyrene-block-polyisoprene copolymers (PS-b-PI) in N,N-dimethyl-acetamide (DMAc) is investigated by static light scattering. DMAc is a polar selective solvent for PS which ensures for sufficient dissociation of ion pairs in solution. The use of polyisoprene as the nonsoluble block provides micelles in thermodynamic equilibrium since PI is a liquid at ambient temperature. Two different types of ionic end functionality are considered: (i) a monofunctional diblock with a lithium sulfonate group at the PI chain end and (ii) an α,ω-macrozwitterionic species with an additional ammonium group at the PS chain end. They are both compared to a neutral diblock of same mass and block sizes (12 kg/mol per block). It is shown that micelles formed by block copolymers containing a sulfonate group at the PI end (core of the micelle) exhibit an aggregation number (Nagg) which is only about 30% of Nagg of the neutral block copolymer. The critical micelle concentration (cmc) in this case is increased by 1 order of magnitude. The macrozwitterionic samples behave qualitatively as the monofunctionalized polymer, however, presenting a larger aggregation number and a lower cmc with respect to the monofunctionalized sample. This effect is attributed to a self-screening mechanism in micelles of the α,ω-macrozwitterions, where counterions are bound through chains of the soluble block