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Using published and new chronosequence datasets from the European Alps and the Wind River Range (Rocky Mountains, USA), we report for the first time a chronosequence of more than 1 Ma for soil organic carbon, nitrogen and organic matter (SOM) fractions from alpine soils. The investigated parameters include total carbon and nitrogen as well as the stable (resistant to H2O2 oxidation) C and N fractions. Time trends were analysed and are reported on the basis of stocks and concentrations. The accumulation rates of C and N strongly decreased with increasing soil age. Differences in trends between the European Alps and the Wind River Range might be attributed to the factor climate. For the drier Wind River Range, an asymptotic value of about 15 kg C m− 2 was reached after about 15 ky while an asymptotic value of 20–25 kg C m− 2 was measured for the moister European Alps after about 3 ky. The difference in N stocks between the two regions was less obvious. For both areas, N was in the range of 0.5–2 kg N m− 2. Using the exponential decay model, a steady state of C and N (stable and total) concentrations in the topsoil seemed to be reached after < 1 ky (Alps) and 10 ky (Wind River Range). The retardation effect observed for the Wind River Range could probably be due to aeolian influx. For both areas, the asymptotic value of the stable fraction of C and N was in the range of 1–3 kg C m− 2 and 0.2–0.4 kg N m− 2, respectively. The stable organic fraction often has an age close to the age of the soils and consequently can reach thousands of years. The relative proportion of N and amides was higher in the stable organic fraction compared to the bulk soil. The sequestration rates of org. C and N in soils of the European Alps and the Wind River Range can reach very high values in very young soils whereas in old soils sequestration rates are several orders of magnitude lower. Old soils often integrate several cold and warm phases and different vegetation types. Nonetheless, the factor Time seems to be very dominant and covers the track of other factors in old soils.

In recent decades laurophylloid vegetation has started to colonise forests of southern Switzerland and northern Italy. The increased colonisation since about 1950 is due to increased winter temperatures and urbanisation. With respect to the changes in the vegetation cover, the question arises as to whether or to which extent they influence soil organic matter quality and chemistry. In southern Switzerland, the common forest vegetation at sites bc. 1000 m a.s.l. consists predominantly of chestnut species (Castanea sativa) that have been introduced approx. 2000–3000 years ago. An older vegetation type, however, would be a Quercetum– Betuletum forest that can still occasionally be found in the area Locarno/Ascona/Cannobio. We studied the short-term influence of the laurophylloid vegetation and also the long-term influence of chestnut on soil characteristics including total organic carbon and nitrogen, pH, CEC, soil lightness and chemical fractions of soil organic matter. The characterisation of the functional groups of fulvic and humic acids was performed using IR-spectroscopy. In general, short-term differences in the C/N ratio and also in the quality and quantity of fulvic and humic acids seem to be likely between laurophyllous and chestnut stands. In general, lower C/N ratios and fulvic and humic acid contents were measured in soils under laurophyllous species. The laurophylloid vegetation gave rise to higher percentages of proteic amides, aliphatic CH₂ and CH₃ and lower C=O amide groups in the fulvic acids. A trend towards a lower humification degree was measurable for the sites with laurophylloid vegetation where organic matter seems to be less resistant to biodegradation. A significant effect of the laurophylloid vegetation on the org. C concentration was, however, not detectable. Chestnut very probably influenced soil organic matter in the long-term by producing lower total C and N contents, by a decrease in soil darkness, a lower amount of humic acids and a decreased CEC as compared to the older Quercetum–Betuletum vegetation. The differences in humus chemistry between chestnut and Quercetum–Betuletum stands were, however, small because the quality of the litter source seems to be similar. The colonisation of laurophyllous species is an obvious indication of human impact and of fast and accelerating climate change that after a few decades already led to a remarkable influence on soil and humus chemistry.

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 60–80 °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.