Das Projekt "Influence of laurophyllous species and chestnut on soil weathering and clay mineral assemblages" wird vom Umweltbundesamt gefördert und von Universität Zürich, Geographisches Institut durchgeführt. In recent decades numerous non-indigenous species of the evergreen broad-leaved (laurophyllous) type have started to colonise forests of southern Switzerland and northern Italy. Since about 1950 many species of the laurophyllous type cultivated in gardens began to spread which is especially due to increased winter temperatures. The colonisation of laurophyllous species is an obvious indication of fast and accelerating climate change that is also likely to be accompanied by the development of long-term ecosystem disequilibria. With respect to the changes in the vegetation cover, the question arises if or to which extent they influence soil mineralogy and chemistry and therefore soil quality. Our study includes the investigation of changes in the soil chemistry and clay mineralogy on selected sites. In southern Switzerland, the common forest vegetation at sites less than c. 1000 m a.s.l. predominantly consists of chestnut species. However, chestnut species do not reflect the original forest vegetation as they have been introduced by the Romans c. 2000 years ago. The older vegetation would be a Quercetum-Betuletum forest that can be occasionally found in the area Locarno/Ascona/Cannobio. We would like to study the long-term influence of chestnut (c. 2000 years) on soil chemistry and clay mineralogy. Our proposed investigation includes, thus, a short-term (c. 40-50 years) and a long-term effect (c. 2000 years) of changing vegetation on soil properties. We assumed that on the long-term as well as on the short-term level changes in the soil will be observable. Special emphasis was given on clay mineralogy and soil organic matter and their qualitative and/or semi-quantitative changes between the sites. Soil mineralogy (clay fraction and fine earth) was studied with XRD and FT-IR. Measurements on some selected samples with Mössbauer spectroscopy allow us to characterize Fe in the oxihydroxides and to identify the specific transformation reactions. Further steps include the determination of weathering losses and of mineralogical transformations in typical soil profiles (down to the C horizon). Due to the expected relation of organic matter composition and clay mineralogy, the quantity of fulvic and humic acids was determined. Additionally, fulvic acids were chemically characterized by IR. These results were compared with the mineralogy to observe mineral-organic matter interactions. The methodological approach allowed to furnish precious details of short- to long-term weathering rates and transformation of mineral phases due to differences in the vegetation.
Das Projekt "Influence of steam sterilisation on soil chemical characteristics, trace metals and clay mineralogy^Valutazione delle modificazioni fisiche, chimiche, biologiche e mineralogiche indotte nel suolo da vari processi di disinfestazione ecologica (FRA)" wird vom Umweltbundesamt gefördert und von Universität Zürich, Geographisches Institut durchgeführt. Soil sterilisation with steam under pressure and additives, such as CaO or KOH that react exothermically in water, is an alternative technology to fumigants. The influence of soil sterilisation (system Bioflash, Ecoflash SC 600) on the chemical behaviour of organic matter, heavy metals (Cd, Cu, Zn and Pb) and clay mineralogy was investigated on three typical soil materials (Ap horizons) with different carbonate contents. These materials were treated in the laboratory in wooden containers. Soil heating produced temperatures ranging between 60°C-80°C for at least 20 min. The treatment generally seemed to increase the pH values and may lead in the long-term to a certain alkalisation with high dosages of CaO or KOH. The effects of the CaO treatment on the K and Ca speciation in the soil were rather small, whereas those of the KOH treatment were more pronounced for K. The addition of KOH favoured the fixation of K in the interlayers of smectite. The XRD measurements were in agreement with the chemical speciation of K. The K chemistry was affected by the treatment by higher contents of the fixed fraction. Organic matter partially decreased after the soil heating treatment. The behaviour of the heavy metals was also affected. In some cases, the EDTA-extractable fractions of Cu, Zn or Pb as well as the soluble fractions of Cu and Zn were distinctly changed after the treatment. The soil-heating treatment probably affected the type and amount of organic ligands and also the adsorbing surfaces that control the solubility of the heavy metals. The heavy metal solubility, however, still remained low after the treatment. The effects of the soil sterilisation on the chemical and mineralogical properties did not seem to be dramatic. It is, however, difficult to predict possible changes if the treatment is repeated over years to decades. We presume that there might be quite substantial effects (especially on the behaviour of organic matter under certain circumstances) in the long term if, as seen at some sites, changes (i.e. decrease) are already measurable after one treatment. Mulching or the addition of organic manure would be possible measures to counter a destabilisation of the soil (i.e. increase in soil erosion susceptibility) and a continuous disintegration of the organic matter pool.