Global Change Abstracts The Swiss Contribution - SCNAT

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114 08.1-199 Effect of climate and vegetation on soil organic carbon, humus fractions, allophanes, imogolite, kaolinite, and oxyhydroxides in volcanic soils of Etna (Sicily) Egli M, Alioth L, Mirabella A, Raimondi S, Nater M, Verel R Switzerland, Italy Agriculture, Soil Sciences , Geology , Geochemistry & Geophysics A soil sequence along an elevational gradient ranging from to subalpine climate zones in the Etna region (Sicily, southern Italy) investigated with respect to organic C, kaolinite, and crystalline noncrystalline Al and Fe phases. Special emphasis was given to stabilization of soil organic carbon (SOC) and its interaction with inorganic phases. The soils were variations of Vitric Andosols developed on a trachybasaltic lava flow with an age of 15,000 years. main vegetation systems dominated the sites: at the lower sites, it mainly maquis vegetation and, at the higher elevated sites, predominantly coniferous forest. The concentration of SOC in the topsoil, SOC stocks in the profiles, the humus fractions such as humic and acids, functional groups and substances of organic matter, type materials (ITM), and oxyhydroxides were found to be related to elevation and, thus, climate (precipitation and temperature) and vegetation. The C/N ratio in the topsoil was especially indicative the vegetation type. The amount of SOC, ITM, and crystalline oxyhydroxides decreased with increasing altitude. Weathering, as to the proportion of crystalline Fe-oxyhydroxides or the kaolinite centration in the clay fraction, seemed to be greater at the lower sites. At these sites, maquis vegetation led to a higher accumulation SOC as compared with the coniferous trees at the higher sites. activity, as indicated by aromatic compounds in the humic acids and the presence of charcoal in the soil, has most probably influenced important soil processes. The identification and radiocarbon dating charcoal revealed evidence that repeated bush fires had played a significant role in soil formation. The better stabilization of SOC at altitudes might be due to the specific climatic conditions with a pronounced change in periods of humidity alternating with periods droughts and resultant fire activity. The positive correlation mean annual temperature and SOC content supports such a hypothesis. The climate- and vegetation-dependent stabilization of organic matter the soil can be ascribed to the proportion of aromatics in the humic acids, to the presence of noncrystalline Al and Fe phases, to the kaolinite concentration, to the amount of clay, and to a lesser extent to the fraction. Soil Science, 2007, V172, N9, SEP, pp 673-691. Global Change Abstracts – The Swiss Contribution | Soil and Lithosphere 08.1-200 Soil moisture - Atmosphere interactions during the 2003 European summer heat wave Fischer E M, Seneviratne S I, Vidale P L, Lüthi D, Schär C Switzerland, England Modelling , Meteorology & Atmospheric Sciences , Agriculture, Soil Sciences The role of land surface-related processes and feedbacks during the record-breaking 2003 European summer heat wave is explored with a regional climate model. All simulations are driven by lateral boundary conditions and sea surface temperatures from the ECMWF operational analysis and 40-yr ECMWF Re-Analysis (ERA-40), thereby prescribing the large-scale circulation. In particular, the contribution of soil moisture anomalies and their interactions with the atmosphere through latent and sensible heat fluxes is investigated. Sensitivity experiments are performed by perturbing spring soil moisture in order to determine its influence on the formation of the heat wave. A multiyear regional climate simulation for 1970-2000 using a fixed model setup is used as the reference period. A large precipitation deficit together with early vegetation green-up and strong positive radiative anomalies in the months preceding the extreme summer event contributed to an early and rapid loss of soil moisture, which exceeded the multiyear average by far. The exceptionally high temperature anomalies, most pronounced in June and August 2003, were initiated by persistent anticyclonic circulation anomalies that enabled a dominance of the local heat balance. In this experiment the hottest phase in early August is realistically simulated despite the absence of an anomaly in total surface net radiation. This indicates an important role of the partitioning of net radiation in latent and sensible heat fluxes, which is to a large extent controlled by soil moisture. The lack of soil moisture strongly reduced latent cooling and thereby amplified the surface temperature anomalies. The evaluation of the experiments with perturbed spring soil moisture shows that this quantity is an important parameter for the evolution of European heat waves. Simulations indicate that without soil moisture anomalies the summer heat anomalies could have been reduced by around 40% in some regions. Moreover, drought conditions are revealed to influence the tropospheric circulation by producing a surface heat low and enhanced ridging in the midtroposphere. This suggests a positive feedback mechanism between soil moisture, continentalscale circulation, and temperature. Journal of Climate, 2007, V20, N20, OCT 15, pp 5081-5099.
Global Change Abstracts – The Swiss Contribution | Soil and Lithosphere 115 08.1-201 Numerical modelling of the hydrogeological and geomechanical behaviour of a large slope movement: the Triesenberg landslide (Liechtenstein) Francois B, Tacher L, Bonnard Ch, Laloui L, Triguero V Switzerland Modelling , Geomorphology , Geology Using advanced hydrogeological and geomechanical finite element modelling, it has been possible to model the mechanical behaviour of a large slope movement, the Triesenberg landslide. This slope is located along the Rhine valley in the Principality of Liechtenstein and covers an area of around 5 km(2), which includes two villages. Pore-water pressure fields calculated by the hydrogeological model were used as input for the geomechanical model. The results obtained through numerical simulation agree fairly well with field measurements of peak velocity, spatial and temporal distribution of velocity, and total displacements. Such results were obtained using a modified Cam-Clay elastoplastic constitutive model for which the required material parameters were obtained through careful geotechnical tests. These finite element models were carried out in two and three dimensions to gradually improve the understanding of the physical phenomena governing the hydrogeological conditions and the movements of the slope. Canadian Geotechnical Journal, 2007, V44, N7, JUL, pp 840-857. 08.1-202 Formation of hydrozincite, Zn layered double hydroxide and Zn phyllosilicates in contaminated calcareous soils Jacquat O, Vögelin A, Kretzschmar R Switzerland Agriculture, Soil Sciences , Geochemistry & Geophysics , Toxicology Geochimica et Cosmochimica Acta, 2007, V71, N15, AUG, SS, p A437. 08.1-203 The impact of Fe isotope fractionation by plants on the isotopic signature of soils Kiczka M, Wiederhold J G, Krämer S M, Bourdon B, Kretzschmar R Switzerland, Austria Plant Sciences , Agriculture, Soil Sciences , Geochemistry & Geophysics Geochimica et Cosmochimica Acta, 2007, V71, N15, AUG, SS, p A482. 08.1-204 Sulphur behaviour in forest soils near the largest SO 2 emitter in northern Europe Koptsik G, Alewell C Russia, Switzerland Forestry , Agriculture, Soil Sciences , Geochemistry & Geophysics , Toxicology , Ecology The impact of 60 a of SO 2 emissions from a Ni- Cu plant in the Kola Peninsula (Russia) on soil S contents was assessed in podzols under pine forests. Sulphate desorption and the possible delay of acidification reversal was investigated, because the plant will be reconstructed in 2006 with an expected emission reduction of 90%. Sites were sampled along a pollution gradient in the prevailing wind direction from 1 to 66 km. The investigated podzols stored S mostly in the organic form. The concentrations of total and organic S in soil organic horizons tended to be higher near the smelter but were only weakly correlated with S deposition. No relationship between distance to smelter and S contents was found for the mineral horizons. Sulphate content and desorption behavior were highly variable due to natural variations of texture and extractable Al and Fe contents of the soils. The lack of a clear strong trend with distance from the smelter except in the organic layer indicated that long range transport and diffuse input of SO 4 played a major role rather than point source impact. It was concluded that biological turnover is most likely the regulating process in these soils and thus low to medium release of SO 4 is expected under decreasing deposition scenarios because organic S was the dominant fraction of total S in all soils. Applied Geochemistry, 2007, V22, N6, JUN, pp 1095-1104. 08.1-205 Evidence for in situ degradation of mono-and polyaromatic hydrocarbons in alluvial sediments based on microcosm experiments with C-13-labeled contaminants Morasch B, Höhener P, Hunkeler D Switzerland, France Microbiology , Geochemistry & Geophysics , Geology A microcosm study was conducted to investigate the degradation of mono- and polyaromatic hydrocarbons under in situ-like conditions using alluvial sediments from the site of a former cokery. Benzene, naphthalene, or acenaphthene were added to the sediments as C-13- labeled substrates. Based on the evolution of C-13-CO 2 determined by gas chromatography isotope-ratio mass spectrometry (GC-IRMS) it was possible to prove mineraliza-
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