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Due to their spatial complexity and dynamic nature, floodplains provide a wide range of ecosystem functions. However, because of flow regulation, many riverine floodplains have lost their characteristic heterogeneity. Restoration of floodplain habitats and the rehabilitation of key ecosystem functions has therefore become a major goal of environmental policy. Many important ecosystem functions are linked to organic carbon (C) dynamics in riparian soils. The fundamental understanding of the factors that drive the processes involved in C cycling in heterogeneous and dynamic systems such as floodplains is however only fragmentary. <br><br> We quantified soil organic C pools (microbial C and water extractable organic C) and fluxes (soil respiration and net methane production) in functional process zones of adjacent channelized and widened sections of the Thur River, NE Switzerland, on a seasonal basis. The objective was to assess how spatial heterogeneity and temporal variability of these pools and fluxes relate to physicochemical soil properties on one hand, and to soil environmental conditions and flood disturbance on the other hand. <br><br> Overall, factors related to seasonality and flooding (temperature, water content, organic matter input) affected soil C dynamics more than soil properties did. Coarse-textured soils on gravel bars in the restored section were characterized by low base-levels of organic C pools due to low TOC contents. However, frequent disturbance by flood pulses led to high heterogeneity with temporarily and locally increased pools and soil respiration. By contrast, in stable riparian forests, the finer texture of the soils and corresponding higher TOC contents and water retention capacity led to high base-levels of C pools. Spatial heterogeneity was low, but major floods and seasonal differences in temperature had additional impacts on both pools and fluxes. Soil properties and base levels of C pools in the dam foreland of the channelized section were similar to the gravel bars of the restored section. By contrast, spatial heterogeneity, seasonal effects and flood disturbance were similar to the forests, except for indications of high CH₄ production that are explained by long travel times of infiltrating water favouring reducing conditions. Overall, the restored section exhibited both a larger range and a higher heterogeneity of organic C pools and fluxes as well as a higher plant biodiversity than the channelized section. This suggests that restoration has indeed led to an increase in functional diversity

Abstract. Due to their spatial complexity and dynamic nature, floodplains provide a wide range of ecosystem functions. However, because of flow regulation, many riverine floodplains have lost their characteristic heterogeneity. Restoration of floodplain habitats and the rehabilitation of key ecosystem functions, many of them linked to organic carbon (C) dynamics in riparian soils, has therefore become a major goal of environmental policy. The fundamental understanding of the factors that drive the processes involved in C cycling in heterogeneous and dynamic systems such as floodplains is however only fragmentary.We quantified soil organic C pools (microbial C and water extractable organic C) and fluxes (soil respiration and net methane production) in functional process zones of adjacent channelized and widened sections of the Thur River, NE Switzerland, on a seasonal basis. The objective was to assess how spatial heterogeneity and temporal variability of these pools and fluxes relate to physicochemical soil properties on one hand, and to soil environmental conditions and flood disturbance on the other hand.Correspondence to: J. Luster (joerg.luster@wsl.ch) Overall, factors related to seasonality and flooding (temperature, water content, organic matter input) affected soil C dynamics more than soil properties did. Coarse-textured soils on gravel bars in the restored section were characterized by low base-levels of organic C pools due to low TOC contents. However, frequent disturbance by flood pulses led to high heterogeneity with temporarily and locally increased C pools and soil respiration. By contrast, in stable riparian forests, the finer texture of the soils and corresponding higher TOC contents and water retention capacity led to high baselevels of C pools. Spatial heterogeneity was low, but major floods and seasonal differences in temperature had additional impacts on both pools and fluxes. Soil properties and base levels of C pools in the dam foreland of the channelized section were similar to the gravel bars of the restored section. By contrast, spatial heterogeneity, seasonal effects and flood disturbance were similar to the forests, except for indications of high CH 4 production that are explained by long travel times of infiltrating water favoring reducing conditions. Overall, the restored section exhibited both a larger range and a higher heterogeneity of organic C pools and fluxes as well as a higher plant biodiversity than the channelized section. This suggests that restoration has indeed led to an increase in functional diversity.

This study examines the role of abiotic (texture, calcium carbonates or iron) and biotic parameters (earthworm and enchytraeid activities) on the initial phases of soil aggregation. Our research focused on humus forms in alluvial soils, which are considered as young and heterogeneous environments. We hypothesized that the soil structure formation is determined by both the nature of the recent alluvial deposits and the soil fauna. For this purpose, six sites were chosen throughout two types of softwood forests (willow and alder forest) representing two stages of vegetation succession. Evidence of soil texture influence on aggregate stability was observed. A dominance of a coarse sand fraction caused a quick colonization of enchytraeids and epigeic earthworms while a silty texture favoured the presence of anecic earthworms, thus increasing the aggregate stabilisation. Iron forms, acting as cementing agents, were observed in the coarse silt, while calcium carbonates were equally distributed among the textural fractions. Active calcium carbonate fraction, binding organic matter with mineral components, was not found in the coarse sand fraction. In conclusion, the tree age cannot alone be used as an indicator of the humus form evolution but biological and physicochemical parameters also influence the initial steps of soil structuration.

This article examines different views of the European Union (EU) legislative decision-making process through a quantitative analysis of all Commission proposals initiated between 1984 and 1999. Using the positions of Member States, the analysis is innovative in two respects: the identification of the relative importance of institutions and preferences for the process of EU legislative decision making, and the empirical evaluation of the ongoing theoretical controversy between constructivists and spatial analysts about the converging or diverging effect of Member State positions. The findings reveal that the process of EU legislative integration is significantly slowing down, even though Council qualified majority voting facilitates decision making while parliamentary participation modestly increases the duration. Against the constructivist claims of convergence, the results show that the divergence of Member State positions significantly determines the duration of the legislative process, in particular in the key domains of EU integration: the larger the distance between the Member States' positions, the longer the EU decision-making process takes. This suggests that the accession of countries with diverging positions will slow down the EU's legislative process, but institutional reform of the Council's decision-making threshold is a promising solution for coping with this effect.Legislative research on European Union (EU) decision making has entered the stage of quantitative analysis, which can advance dialogue by evaluating where one competing approach applies, controlling for other approaches (Jupille et al. 2003: 29). After years of single proposition studies, 1 rich and systematic data analyses on the process of EU legislative decision making can help answer the most important questions of EU scholars that are raised in the debate not only between spatial analysts 2

a b s t r a c tIn many terrestrial ecosystems, soil parameters usually regulate the distribution of earthworm communities. In alluvial ecosystems, few studies have investigated the impact of periodic floods and alluvium deposition on soil fauna. In this context, we assumed that earthworm communities may vary depending on altitude (alpine, subalpine, mountain and hill levels), forest successional stage (post-pioneer to mature forests) and some soil parameters. Our results demonstrated that the composition of earthworm communities differed depending on altitudinal gradients. No earthworm was found at the alpine level while maximum density and biomass were observed at the hill level mainly due to the contribution of anecic species. A total of 27 species and subspecies were found over the three sampling sites, and Lumbricus moliboeus was discovered for the first time in carbonated soils. Soil texture had a major effect on epigeics that were often associated with coarse sandy texture in contrast to anecics which preferred deep soils and mature forest stages, which in combination provided the highest carbon content and the finest soil texture. In our study, carbonated fluviosols (Fluvisols according to the World Reference Base) were recorded; fluviosols typiques with well-structured A layers were generally found in mature or intermediate forest stages while most of fluviosols juveniles with heterogeneous texture were observed principally in post-pioneer forests. We conclude that in alluvial ecosystems, earthworm communities were highly dependent first on soil parameters, then altitude and to a lesser extent forest successional stages. Changes in earthworm communities tend to reflect a gradient of alluvial dynamics thus reinforcing the potential role of earthworms as bioindicators in natural and/or semi natural alluvial ecosystems.

In temperate forests, soils are the main sink for atmospheric N deposition. The main processes proposed for N retention are microbial and abiotic immobilization in soil organic matter. The relative importance of these processes as well as the kind of resulting chemical compounds are not totally understood. We carried out a laboratory incubation of Hg-sterilized and non-sterilized organic and organo-mineral soil horizons, labelled with either 15 NO 3 À or 15 NH 4 þ . The labelled samples were incubated for 1 hour, 1 day, or 6 days, then subjected to K 2 SO 4 extraction and analysed with 15 N CPMAS NMR spectroscopy. N immobilization was already effective in all samples and treatments after 1 hour. The corresponding NMR spectra showed that part of the immobilized 15 N was already incorporated into an amide structure. In the sterilized soils labelled with 15 NH 4 þ , the tracer was rapidly and largely immobilized by an unknown process related to the presence of Hg. In the sterilized soils labelled with 15 NO 3 À , between one-third and one-half of the added tracer was immobilized during the first hour and only 10% more over the 6 days. These results suggest that the sterilization was incomplete at first, allowing relatively great microbial immobilization during the first hour. By contrast, over a longer time, NO 3 À immobilization was significantly reduced to a level corresponding to an abiotic process as Hg sterilization became more effective. Even if the low signal-to-noise ratio precluded quantitative 15 N NMR measurements, we showed that the amide-peptide signal, considered as a biotic signature, was dominant in all cases. RésuméDans les foreˆts tempe´re´es, les sols constituent le puits principal vis-a`-vis des apports atmosphe´riques azote´s. Deux processus sont a`l'origine de la re´tention de l'azote dans le sol, l'immobilisation microbienne et l'immobilisation abiotique sur la matie`re organique. L'importance relative de ces deux processus ainsi que les formes chimiques qui en re´sultent ne sont pas e´lucide´es. Nous avons mene´au laboratoire une expe´rience d'incubation qui porte sur des horizons organiques, organo-mine´raux, ste´rilise´s ou non a`Hg et marque´s ou non a`1 5 NO 3 À ou 15 NH 4 þ . Suite aù ne incubation d'une heure, d'un jour et de 6 jours, des extractions chimiques a`K 2 SO 4 et de la N CPMAS spectroscopie de Re´sonance Magne´tique Nucle´aire ont e´te´re´alise´es sur les e´chantillons marque´s 15 NO 3 À , 15 NH 4 þ . Apre`s une heure, on note une immobilisation de l'azote dans tous les e´chantillons de sol, quelque soit le traitement effectue´. Les spectres RMN correspondant indiquent qu'une partie du 15 N immobilise´est sous forme d'amides. Dans les e´chantillons ste´rilise´s marque´s a`1 5 NH 4 þ , le traceur est rapidement et massivement immobilise´par un processus non identifie´et lie´a`la pre´sence de Hg. Dans les sols ste´rilise´s marque´s a`1 5 NO 3 À , entre un tiers et la moitie´de la quantite´du traceur sont immobilise´s au cours de la premie`re heure. Au cours des 6 jours suivants...

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