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Deadwood is known to significantly contribute to global terrestrial carbon stocks and carbon cycling, but its decay dynamics are still not thoroughly understood. Although the chemistry of deadwood has been studied as a function of decay stage in temperate to subalpine environments, it has generally not been related to time. We therefore studied the decay (mass of deadwood, cellulose and lignin) of equal-sized blocks of Picea abies wood in soil-mesocosms over two years in the Italian Alps. The 8 sites selected were along an altitudinal sequence, reflecting different climate zones. In addition, the effect of exposure (north- and south-facing slopes) was taken into account. The decay dynamics of the mass of deadwood, cellulose and lignin were related to soil parameters (pH, soil texture, moisture, temperature) and climatic data. The decay rate constants of Picea abies deadwood were low (on average between 0.039 and 0.040y(-1)) and of lignin close to zero (or not detectable), while cellulose reacted much faster with average decay rate constants between 0.110 and 0.117y(-1). Our field experiments showed that local scale factors, such as soil parameters and topographic properties, influenced the decay process: higher soil moisture and clay content along with a lower pH seemed to accelerate wood decay. Interestingly, air temperature negatively correlated with decay rates or positively with the amount of wood components on south-facing sites. It exerted its influence rather on moisture availability, i.e. the lower the temperature the higher the moisture availability. Topographic features were also relevant with generally slower decay processes on south-facing sites than on north-facing sites owing to the drier conditions, the higher pH and the lower weathering state of the soils (less clay minerals). This study highlights the importance of a multifactorial consideration of edaphic parameters to unravel the complex dynamics of initial wood decay.

The importance of gradual erosion relative to landsliding depends predominantly on the slope angle. One factor of critical influence in landsliding along with slope angle and slope shape is the soil depth. Understanding soil depth development on steep topography is fundamental for understanding and predicting the occurrence of landsliding at threshold landscapes. We develop a model to predict soil depth that addresses both threshold and gradual processes. If erosion is a gradual process, soil depth increases until the soil production rate no longer exceeds the erosion rate, and steady state is reached. The predicted soil depth (x) is proportional to the ratio of the infiltration to the erosion rate. Identifying a predictive result for erosion as a function of slope angle (S) allows a test of both the erosion and soil production models with field observations. The same theoretical approach to soil production should be applicable when the principal erosion process is shallow landsliding. After landslides, soil recovery initially follows our predicted power law increase in time, though with increasing time background erosion processes become important. At a time equal to a landslide recurrence interval, the soil depth can exceed the steady state depth by as much as a factor 2. By comparing predicted and observed x(S) results, we show that the accessed result for erosion as a function of slope angle is accurate. Soils deeper than the depth predicted at the landslide recurrence interval are beyond the stability limit. This result suggests an important practical relevance of the new soil production function.

At mid-latitudes, the transition from the Pleistocene to the Holocene was characterised by distinct and partially abrupt climatic changes. Also during the Holocene, climatic perturbations, with sometimes cold-dry conditions, have occurred. How land surfaces and soil development processes in high-mountains respond to these climatic oscillations is so far only poorly known. We traced the responses of surfaces in the alpine settings of the Wind River Range (Wyoming, US) by using a large mire as natural archive. This enabled us to reconstruct environmental conditions and ecosystem changes during the Holocene in this montane area. Although adjacent moraine deposits display 10Be exposure ages from the Last Glacial Maximum up to MIS16 or even older, the accessible sediment deposits covered only the Holocene (via radiocarbon dating). By applying a geoforensic approach and deriving sedimentation rates, major climatic signals were detected. A higher deposition (and consequently erosion) rate and thus a higher rate of geomorphic activity was measured for the known cold periods 9.4–10.2 ka BP, 4.2 ka BP and 2.5 ka BP. During the LIA, especially rapid aggradation of organic matter organic matter took place here. Rates of chemical weathering and soil formation seem to have been relatively low until about 5–6 ka BP but have since increased during the Late Holocene. This would fit previous observations of increasing moisture conditions after the mid-Holocene aridity period. In contrast to several other studies, no clear signs of major disturbances (erosion, weathering) during the 8.2 ka event could be observed. Together with the low levels of chemical weathering found here, we do not see any evidence that the climate was more humid during this period. Compared to previous findings, more humid conditions seemed to have returned earlier, i.e. about 5 kyr BP. In general, this landscape displayed a patchy pattern of reaction to environmental changes, as all events were not recorded in each mire profile., Geomorphology, 371, ISSN:0169-555x, ISSN:1872-695X

Recent modeling and comparison with field results showed that soil formation by chemical weathering, either from bedrock or unconsolidated material, is limited largely by solute transport. Chemical weathering rates are proportional to solute velocities. Nonreactive solute transport described by non-Gaussian transport theory appears compatible with soil formation rates. This change in understanding opens new possibilities for predicting soil production and depth across orders of magnitude of time scales. Percolation theory for modeling the evolution of soil depth and production was applied to new and published data for alpine and Mediterranean soils. The first goal was to check whether the empirical data conform to the theory. Secondly we analyzed discrepancies between theory and observation to find out if the theory is incomplete, if modifications of existing experimental procedures are needed and what parameters might be estimated improperly. Not all input parameters required for current theoretical formulations (particle size, erosion, and infiltration rates) are collected routinely in the field; thus, theory must address how to find these quantities from existing climate and soil data repositories, which implicitly introduces some uncertainties. Existing results for soil texture, typically reported at relevant field sites, had to be transformed to results for a median particle size, d50, a specific theoretical input parameter. The modeling tracked reasonably well the evolution of the alpine and Mediterranean soils. For the Alpine sites we found, however, that we consistently overestimated soil depths by ~45%. Particularly during early soil formation, chemical weathering is more severely limited by reaction kinetics than by solute transport. The kinetic limitation of mineral weathering can affect the system until 1 kyr to a maximum of 10 kyr of soil evolution. Thereafter, solute transport seems dominant. The trend and scatter of soil depth evolution is well captured, particularly for Mediterranean soils. We assume that some neglected processes, such as bioturbation, tree throw, and land use change contributed to local reorganization of the soil and thus to some differences to the model. Nonetheless, the model is able to generate soil depth and confirms decreasing production rates with age. A steady state for soils is not reached before about 100 kyr to 1 Myr

The European Alps are a geomorphologically active region and experience a number of gravity-driven hillslope processes. Soil and landscape formation in the Alps has consequently undergone several minor and major traceable changes of developmental trajectories during the Holocene. Soil development is hypothesised to be often non-linear with time and characterised by stages of progressive and regressive evolution caused by upbuilding (formation, profile deepening) and erosion (profile shallowing). Several cold and warm climate phases are identified during the Holocene but it is largely unknown which effects these might have had on slope processes. By using datable moraines ( 10 Be) and mires ( 14 C), we have constructed a temporal framework for these processes. Using the geochemical imprint of mires in the Alpine setting of the Goschener-valley of the Central Swiss Alps, we reconstructed general (mostly erosional) landscape processes for the last ca. 10 ka. As this is the type locality for the Goschener cold phase, we assumed that this phase (Goschener cold phase I and II ~ 1.5 and ~ 2.5 ka BP) should have left easily recognizable traits. After deglaciation (11–12 ka BP), soil evolution was progressive. Beginning around 8 ka BP, we detect a distinct increase in erosion here, together with a vegetation change (towards tundra vegetation) and the highest measured rates of carbon sequestration. Other phases of high geomorphic activity were recognised ca. 5–6 ka BP, 4 ka BP and, to a lesser extent, 1–3 ka ago. The cold phase at 5–6 ka BP corresponds to a less distinct change in vegetation and lessened erosion. Human impact is increasingly obvious since about 2.4 ka BP which overlaps with the Goschener cold phase. Nonetheless, erosion processes were not extraordinarily high during this period and a climate effect cannot be distinguished. We detect evidence of increasing human disturbance (regressive soil evolution) for about the last 1 ka. We also detect an increase in dust flux during the last ca. 4–5 ka, presumably due to the landscape change(s) in the Sahara during this time.

Purpose: The present work focuses on cold alpine soils of the Altai Mountains (Siberia, Russia). Permafrost is widespread and often occurs at a depth of about 100cm. The area is characterised by extremely cold winters and cool summers: the aim was consequently to find out whether weathering could be more intense on thermally less unfavoured conditions or whether the abundance of water could be a more important factor. Materials and methods: We investigated 10 soils in a very small area close to a local glacier tongue. Five of the investigated soils were south-facing and the other five north-facing. The soils have the same parent material (mica-rich till), altitude, topography and soil age. The vegetation is alpine grassland that is partially intersected with some juniper and mosses. Soil chemical properties such as organic C, N, soil organic matter quality (using DRIFT), pH value, (oxy)hydroxides, total elemental contents (XRF) and soil micromorphology and mineralogy (using diagnostic treatments and XRD) were determined. The age constraint of the site was given by geomorphic studies together with 14C dating of a nearby peat bog and the stable organic matter fraction of the soils. Results and discussion: The soils have a Holocene age. The results showed astonishingly clearly—similarly to the European Alps—that the north-facing soils have a higher weathering state. This is expressed by lower pH values, higher oxalate and dithionite extractable Fe, Al, Mn and Si contents, higher C and N concentrations and stocks when compared to the south-facing sites. No statistically significant differences with respect to weathering indexes could be detected. The geochemical evolution of the soils seems to be enhanced at north-facing sites, even though very severe climatic conditions prevail. Furthermore, biodegradation seems to be less pronounced on north-facing compared to south-facing sites as poorly degraded organic matter is accumulated. This gives rise to more organic ligands that promote metal binding and their subsequent eluviation along the soil profile. Conclusions: We consequently must assume that weathering is not limited by low temperatures in the active layer but is rather controlled by soil moisture that seems to be higher during the warmer period in the north-facing soils.

The aim of this work was to detect imprints on soil properties from former Islamic land use (9th to 11th century) using a multi-method, soil-chemical approach. Four soil profiles (with buried horizons) found in the vicinities of former Islamic settlements in Sicily were analysed for phosphorus (total, organic and inorganic), nitrogen (total, NO 3 − and NH 4 + ), carbon compounds (δ 13 C, lipids, polycyclic aromatic hydrocarbons (PAH) and functional groups), physical and chemical C-fractions and the state of soil weathering. Two soil profiles contained ceramic sherds from the Islamic period. Inorganic nitrogen forms, phosphorous and the PAH content indicated strong impacts from traditional agriculture and/or burning. Radiocarbon dating of soil organic carbon (SOC) fractions from buried horizons showed that distinct changes must have occurred during the Islamic epoch. The isotopic composition of SOC indicated that land use was probably different in earlier times. C 4 plant cultivation was expected but surprisingly lipid analyses did not confirm this. A high amount of aliphates and low C/N ratio indicated a good, long-term SOC stabilisation under the native conditions combined with Islamic land use. The irrigation of the soils probably increased the production of weakly-crystalline Fe forms that helped to stabilise SOC. The multi-method approach was very helpful in deciphering human-induced processes. Although a full proof for each parameter is not given, former Islamic land-use seems to have distinctly affected the soils – not only locally but probably also in other areas of Sicily, Northern Africa, Near East and Iberian Peninsula.

An important result of the past few decades of soil–geomorphic research is the awareness of the major role of dust and related carbonate precipitates in arid soils. The temporal evolution of soils developed on outwash terraces is still a matter of debate particularly regarding the type of evolution: progressive evolution and constant rates vs complex and/or interval-accumulation rates (progressive or regressive evolution possible). Soils on a chronosequence of outwash terraces just outside and downstream of canyon mouths of the Wind River Range (USA) were analysed for carbonate accumulation, organic carbon and poorly-crystalline pedogenetic oxyhydroxides stocks and pathways of chemical weathering. The soils and their carbonate stocks in the fine earth fraction (< 2 mm) can be used as a relative dating tool and appear to correlate with regional glacial chronostratigraphy [Pinedale (c. 20 ky), Bull Lake (with two different units around 160 and 260 ky) and Sacagawea Ridge (c. 660 ky)]. Carbonate stocks of soils on these terraces increase with increasing soil age, but at generally decreasing rates. A quasi-steady state situation, however, was not reached before 1 My. The time-split approach showed that CaCO3 accumulation rates were the highest during marine isotope (MIS) cold stages (2.13 g CaCO3/m2/y), presumably due to a sparse vegetation cover during MIS2 (Pinedale) and 8 (lower Bull lake). Compared to organic carbon (c. 8–10 kg Corg/m2), the inorganic carbon stocks of the fine earth fraction were much higher (c. 60 kg Cinorg/m2). Although the dominant pedogenic process here appears to be carbonate accumulation, chemical weathering and elemental leaching also are significant. Weathering data were obtained using immobile elements and rare earth elements (REE) as tracers. Chemical weathering and related leaching were particularly notable for Na originating from plagioclase. In addition, pedogenetic Al and Mn oxyhydroxides accumulate (220 and 32 g/m2, respectively, after 660 ky). These form at relatively low rates, however, when compared to moister and cooler conditions at higher altitudes in the Wind River Range. Due to the dry climate under which the terrace soils formed (annual precipitation 32 cm/yr− 1), weakly crystalline and amorphous Fe-oxyhydroxide is rapidly transformed into crystalline forms (hematite) over time. Consequently, the stocks of weakly crystalline and amorphous Fe-oxyhydroxide was significantly lower in the ~ 660 ky soils (50 g/m2) than in the Holocene soils (1000 g/m2). The development of soils on Quaternary outwash terraces in this region is controlled through the rates of aeolian influx over time as modified by glacial/interglacial climate variations rather than by moisture availability. Consequently, carbonate accumulation rates in these soils are ‘influx limited’ rather than ‘moisture limited’.

Only scarce information is available on how organic C is incorporated into the soil during the decay and how (micro) climate influences this process. Therefore, we investigated the effect of exposure and elevation on the organic litter decomposition and C-stabilisation in acidic soils of an Alpine environment. An experiment with artificially 13C labelled Norway spruce needles was carried out at north- and south-exposed sites between 1200 and 2400 m a.s.l. in the Italian Alps using mesocosms. After 1 year, the 13C recoveries of the bulk soil were 18.6% at the north-facing slopes and 31.5% at the south-facing slopes. A density fractionation into a light (LF; ≤1.6 g cm−3) and a heavy fraction (HF; >1.6 g cm−3) of the soil helped to identify how the applied substrate was stabilised. At the northern slope, 10.5% of the substrate was recovered in the LF and 8.1% in the HF and at the south-facing slope 22.8% in the LF and 8.1% in the HF. The overall 13C recovery was higher at the south-facing sites due to restricted water availability. Although the climate is humid in the whole area, soil moisture availability becomes more important at south-facing sites due to higher evapotranspiration. However, at sites >1700 m a.s.l, the situation changed, as the northern slope had higher recovery rates. At such altitudes, temperature effects are more dominant. This highlights the importance of locally strongly varying edaphic factors when investigating the carbon cycle.

To describe the decay stage of coarse woody debris (CWD) a five decay-class system has been introduced and it is currently the most commonly applied. This system is based on visual, geometric and tactile features of the wood in the field; however, a detailed chemical characterization is often missing. Furthermore, the driving mechanisms (particularly substrate quality vs. environmental conditions) of deadwood decay are controversially discussed. Consequently, we investigated how typical major and minor chemical parameters of wood were correlated with the decay stage. The decomposition patterns of Norway spruce (Picea abies (L.) Karst) and European larch (Larix decidua Mill.) CWD of an Alpine setting were analyzed, and how the chemical and physical parameters were affected by the substrate and environmental conditions was checked. Two altitudinal sequences, having a different exposure (north- vs. south-facing sites), were sampled. We measured main biochemical compounds (lignin and cellulose), physical properties (density and water content), element concentrations (C, N, P, K, Ca, Mg, Fe, Mn), and the carbon isotopic signature (δ13C) of living trees and CWD at five decomposition stages (decay classes). Most investigated wood physico-chemical parameters such as wood density, water content, lignin and cellulose and even minor constituents (N, Ca, Mg, P, Fe, Mn) correlated well to the five decay-class system. Some important components, such as the carbon concentration and δ13C, did not vary with increasing decomposition. Our hypothesis that the different substrate should be traceable during CWD decay had to be rejected, although some statistically significant chemical differences between larch and spruce were measured in the living trees. The chosen tree species were probably not different enough to be chemically traceable in the CWD. Already in decay class 1, these differences were zeroed. The site conditions (expressed by the different altitudes and exposure) influenced only some of the investigated parameters, namely lignin, the δ13C isotopic ratio and nutrients such as P, Ca and K.

Soil erosion processes are one of the main threats to the Alps. They affect slope stability, water budgets, vegetation productivity and the overall biodiversity of the alpine ecosystem. In particular, recent land use and climate changes exacerbated the impact that sheet erosion, a dominant but scarcely visible process, has on alpine grasslands. Yet, the quantitative estimation of the effects of sheet erosion is constrained by the topographic and climatic conditions of the Alps, which hinder the application of conventional assessment techniques. Recently, the use of fallout radionuclides (FRN) as soil erosion tracers showed very promising results in deriving integrated estimates of soil degradation processes affecting alpine soils, over a range of different time scales. Nonetheless, for a correct application of the FRN method, special attention should be paid to three main critical points that are extensively discussed in this thesis, namely: (i) the selection of suitable reference sites; (ii) the selection of the approach (i.e. the traditional approach, the resampling approach, or the repeated sampling approach); and (iii) the selection of the appropriate conversion model. First, we investigated the suitability of undisturbed reference sites in an alpine valley (Urseren Valley, Canton Uri, Switzerland) for the application of 137Cs, the most commonly used FRN for soil erosion studies. In alpine regions, which are heavily affected by the heterogeneous Chernobyl 137Cs fallout and by high geomorphic and anthropogenic activity, the choice of reference sites is a great challenge. To avoid the uncertainties associated with a wrong selection of reference sites, we have developed and proposed the decision support tool CheSS, which allows Checking the Suitability of reference Sites using a repeated sampling strategy and a decision tree. Comparing the 137Cs inventories of reference sites, which have been sampled in two different periods, enables identifying the sites where no soil disturbance processes have occurred and that can be further used as a stable and reliable basis for the application of the method. Chess also directs particular attention to the analysis of the spatial variability of the 137Cs distribution at the sites. The results of the Chess application to our study area imply that no suitable reference sites could be found. As a further step, we have tested the application of a 137Cs repeated sampling approach in the Piora Valley (Canton Ticino, Switzerland), where previous studies have failed to identify undisturbed and homogeneous reference sites. The repeated sampling approach facilitates the derivation of short-term soil redistribution rates by comparing the FRN inventories measured at sampling sites in different times, thus without the need of reference sites. Twelve points located along four transects have been sampled in 2010 and in 2014, and their 137Cs inventory has been compared. The results indicate high soil degradation dynamics, which correspond to a range of yearly soil redistribution rates of 3-36 t ha-1. At both study areas, the high difficulties associated with the use of 137Cs as tracers (i.e. the extremely high small-scale variability of 137Cs distribution) led us to examine the applicability of 239+240Pu (also an artificial FRN), whose presence in the Alps is not connected to the Chernobyl fallout, but mainly to the atmospheric nuclear weapon tests. As a result, its distribution is much more homogeneous compared to 137Cs. 239+240Pu is also preferable to 137Cs, because it has a longer half-life and its measurements are more cost- and time-effective. However, the conversion of 239+240Pu inventories into soil redistribution rates has been impeded by the fact that the available models are not able to describe the specific behavior of Pu isotopes in the soil, as they are mainly designed for 137Cs. Consequently, our energy has been directed towards developing a new conversion model, called MODERN (Modelling Deposition and Erosion rates with fallout RadioNuclides). MODERN is an innovative model based on a single formula that derives both soil erosion and deposition rates. MODERN accurately depicts the soil profile shape of any selected FRN at reference sites and allows the adaptation of the depth profile to simulate the behavior of the FRN under different agro-environmental conditions. A first application of MODERN has been performed on a 239+240Pu dataset collected in the Urseren valley. Thanks to its characteristics and its adaptability, MODERN describes the specific depth distribution of Pu isotopes in the soil better than other models. The MODERN code has been developed in Matlab™ and is publically released on the website of our research group. In order to expand its accessibility, the new package modeRn has been recently developed using the free and open-source system R. modeRn also includes new features that enhance its potential and usability. This thesis offers a detailed overview of the difficulties associated with the application of FRN in alpine areas. It also presents new, effective, and useful tools that help reduce the sources of uncertainty of the FRN method (CheSS) and promote its application to derive soil redistribution rates at different land use conditions (MODERN). Future studies should focus on using precise and accurate FRN-based estimates to validate large-scale modelling techniques, in order to improve the monitoring and identification of soil erosion risk areas in alpine regions.

Due to the large size (e.g. sections of tree trunks) and highly heterogeneous spatial distribution of deadwood, the timescales involved in the coarse woody debris (CWD) decay of Picea abies (L.) Karst. and Larix decidua Mill. in Alpine forests are largely unknown. We investigated the CWD decay dynamics in an Alpine valley in Italy using the chronosequence approach and the five-decay class system that is based on a macromorphological assessment. For the decay classes 1–3, most of the dendrochronological samples were cross-dated to assess the time that had elapsed since tree death, but for decay classes 4 and 5 (poorly preserved tree rings) radiocarbon dating was used. In addition, density, cellulose, and lignin data were measured for the dated CWD. The decay rate constants for spruce and larch were estimated on the basis of the density loss using a single negative exponential model, a regression approach, and the stage-based matrix model. In the decay classes 1–3, the ages of the CWD were similar and varied between 1 and 54 years for spruce and 3 and 40 years for larch, with no significant differences between the classes; classes 1–3 are therefore not indicative of deadwood age. This seems to be due to a time lag between the death of a standing tree and its contact with the soil. We found distinct tree-species-specific differences in decay classes 4 and 5, with larch CWD reaching an average age of 210 years in class 5 and spruce only 77 years. The mean CWD rate constants were estimated to be in the range 0.018 to 0.022 y−1 for spruce and to about 0.012 y−1 for larch. Snapshot sampling (chronosequences) may overestimate the age and mean residence time of CWD. No sampling bias was, however, detectable using the stage-based matrix model. Cellulose and lignin time trends could be derived on the basis of the ages of the CWD. The half-lives for cellulose were 21 years for spruce and 50 years for larch. The half-life of lignin is considerably higher and may be more than 100 years in larch CWD. Consequently, the decay of Picea abies and Larix decidua is very low. Several uncertainties, however, remain: 14C dating of CWD from decay classes 4 and 5 and having a pre-bomb age is often difficult (large age range due to methodological constraints) and fall rates of both European larch and Norway spruce are missing.

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 this study we compare newly-developed chemical weathering data with previously published data from soils developed along two chronosequences of glacial deposits in the European Alps and the Rocky Mountains (Wind River Range, USA). By combining these chronosequences, we are able to present a comprehensive dataset that represents a time period of > 1 Ma. We describe weathering trends of important elements using a number of weathering indices (e.g., K + Ca/Ti ratio, the weathering ‘index B’ of Kronberg and Nesbitt (1981) and the open mass transport function). Further, we describe the accumulation of Al, Fe, Si and Mn oxyhydroxides (including partially organic phases) as a function of time, and derive the corresponding accumulation rates. We calculated pedogenetically formed oxyhydroxides using an approach based on immobile elements. Our study represents one of only a few studies that describe rates of soil chemical weathering over a period as long as ~ 1 Ma. Results show that rates of chemical weathering clearly decrease along the chronosequences with increasing age of the soils. We find weathering rates are nearly four orders of magnitude lower in the 1 Ma-old soils than in the young soils. Our results suggest that the older soils may be reaching a steady state for these chemical properties in their present environments. A power function best explains the measured time-trends of the ‘index B’ and (K + Ca)/Ti) ratios in the soils. The best time-trend model for pedogenic weakly- to poorly crystalline phases and the relative losses/gains (based on the open-system mass transport function) were obtained with an exponential decay model function. In terms of the soil system, the decreases in the accumulation rate of the oxyhydroxides appears to be influenced not only by the factor of time but by climate as well (increased precipitation at higher altitudes slows the decrease in weathering rate over time). Thus, our ~ 1 Ma chronosequences also become pedogenic gradients since we describe variations in soil properties along biogenic gradients.

Peat and lake sediments as well as a nearby soil catena were sampled to reconstruct the environmental history of a small infilled lake basin (mire) in the central alpine foreland of Switzerland. Soil evolution is best regarded as discontinuous over time and conceptualised by ‘progressive’ or ‘regressive’ process phases. We analysed the surrounding soils and used corresponding pedosignatures in the mire sediments to characterise notable phases of erosion and deposition. We assumed that the mire sediments would reflect these phases, that elemental composition (major and minor compounds) and rare earth elements (REEs) would allow us to differentiate past processes and that progressive and regressive phases of soil development can be discerned. Although radiocarbon ages are equivocal, it appears from pollen analyses that a lake was present here by c. 45 ka BP. After the retreat of the glacier from this area following the LGM, continuous sedimentation occurred until a mire developed during Pleistocene–Holocene transition. This transition period was accompanied by more intense erosion, as characterised by chemical signatures. A stable phase developed between c. 10–5 ka BP giving rise to progressive soil evolution. Between 5 and 4 ka BP, evidence appears for several erosional phases, predominantly detectable at the margin of the mire. These erosion phases, coupled with accumulation in the mire, are even more evident after 4 ka BP and especially after 2.1 ka BP. Based on soil investigations, elemental fluxes are detected along the slopes with distinct accumulations at the footslope. Evidence for anthropogenic influences and subsequent regressive soil formation phases appear in this pre-alpine landscape about 5 ka BP (Neolithic/Early Bronze Age), which appears to intensify after 2.1 ka BP (Roman period to present). Multi-elemental signatures enabled us to identify the important geochemical processes that have occurred here. Together with radiocarbon and pollen analyses, we placed these processes in a logical temporal context. The use of lacustrine (lake or mire) sediments has great potential to decipher and detail the surrounding landscape history and soil evolution of this region of Switzerland.

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.

At middle to high latitudes, many alpine valleys have been shaped by glaciers associated with periods of Pleistocene glaciation. Present glaciated valleys are characterised by broadened valley floors and U-shaped cross sections, continuously formed by glacial activity from initially V-shaped, fluvial cross sections. Sinks Canyon (Wind River Range, USA) is a glaciated valley characterised by a typical U-shaped cross section, containing till from several glacial advances over a range of at least 1 Ma. The morphostratigraphic records indicate a fourfold difference in ice surface elevation between the youngest and oldest glacial periods, which is not easily explained by the present-day valley topography. To assess possible evolution scenarios of Sinks Canyon, we modelled the palaeovalley topography using a geographic information system (GIS) filtering technique in combination with temporal reference points from relative and numerically dated glacial deposits. Ice thicknesses were calculated using the shallow ice approximation. In our model, the valley became shallower and the topography smoother with increasing years back in time. The results suggest that valley topography with ages between 640 and 1000 ka can clearly be distinguished from the present-day topography. Surfaces with ages of 130–200 ka (attributable to MIS 6; Bull Lake glaciation) still could be discerned from present-day topography, but with relatively high uncertainties. The method did not work for topography less than ~ 100 ka or older than ~ 1 Ma. Erosion depths were calculated using the differences between present-day elevation and the modelled surfaces. Calculated erosion rates were within the range of reference values for glacial erosion (0.001 to 1 mm a− 1). Glacial erosion appears to have removed 0.52 to 0.72 mm a− 1 of rock within a time frame of 1 Ma, assuming 200 ka of aggregated glacial flow. If the glacial occupation was longer or the impact of fluvial erosion was not negligible (as assumed), then the calculated rate is lower. If the model assumes a less extended time of glacial flow (< 100 ka), the rate exceeds 1 mm a− 1. The method used for surface reconstruction and erosion rates calculation is highly dependent on (i) the reliability of the temporal anchor points and (ii) the assumption of physical glacier conditions (basal shear stress).

High-mountain soils develop in particularly sensitive environments. Consequently, deciphering and predicting what drives the rates of soil formation in such environments are a major challenge. In terms of soil production or formation from chemical weathering, the predominating perception for high-mountain soils and cold environments is often that the chemical weathering ‘portion’ of soil development is temperature-inhibited, often to the point of non-occurrence. Several concepts exist to determine long-term rates of soil formation and development. We present three different approaches: (1) quantification of soil formation from minimally eroded soils of known age using chronosequences (known surface age and soil thickness — SAST), (2) determination of soil residence times (SRT) and production rates through chemical weathering using (un)stable isotopes (e.g. 230 Th/ 234 U activity ratios), and (3) a steady state approach using cosmogenic isotopes (e.g. 10 Be). For each method, data from different climate zones, and particularly from high-mountaINS (alpine environment), are compared. The SAST and steady state approach give quite similar results for alpine environments (European Alps and the Wind River Range (Rocky Mountains, USA)). Using the SRT approach, soil formation rates in mountain areas (but having a temperate climate) do not differ greatly from the SAST and steady state approaches. Independent of the chosen approach, the results seem moderately comparable. Soil formation rates in high-mountain areas (alpine climate) range from very low to extremely high values and show a clear decreasing tendency with time. Very young soils have up to 3–4 orders of magnitude higher rates of development than old soils (10 5 to 10 6 yr). This apparently is a result of kinetic limits on weathering in regions having young surfaces and supply limits to weathering on old surfaces. Due to the requirement for chemical weathering to occur, soil production rates cannot be infinitely high. Consequently, a speed limit must exist. In the literature, this limit has been set at about 320 to 450 t/km 2 /a. Our results from the SAST approach show, however, that in alpine areas soil formation easily reaches rates of up to 800–2000 t/km 2 /a. These data are consistent with previous studies in mountain regions demonstrating that particularly young soils intensively weather, even under continuous seasonal snowpack and, thus, that the concept of ‘temperature-controlled’ soil development (soil-forming intervals) in alpine regions must be reconsidered.

Soil organic matter (SOM) can directly be affected by wildfires, both in terms of quantity and quality. The combustion is often incomplete, leading to the formation of pyrogenic organic matter (PyOM), a highly heterogeneous material with prevailing aromatic nature. Focusing our attention on PyOM, we investigated an altitudinal soil sequence on Mount Etna, Italy, ranging from 500 m to 1800 m asl, where the fire frequency is assumed to have been higher at lower elevations due to a warmer and drier climate. We evaluated the effect of fire on the chemical and physical characteristics of SOM along the altitudinal sequence. At two sites at a similar altitude but having a different recent fire history, we also examined the effect of fire frequency on SOM. Chemical oxidation of SOM with acid dichromate was used to evaluate the contribution of pyrogenic organic carbon to total SOC. Furthermore, four SOM density fractions were separated and characterised for principal composition, spectroscopic properties by Diffuse Reflectance Infrared Fourier Transform (DRIFT) and Nuclear Magnetic Resonance (NMR), and particle morphology by Scanning Electron Microscopy (SEM). The stocks of C and N as well as the chemical oxidation resistant carbon (COREC) increased with decreasing altitude, hence supporting the hypothesis of higher fire frequency at lower altitudes. The highest C concentrations were found in the density fraction 1.0–1.6 g cm − 3 . At the lower sites, a considerable amount of aromatics, and hence a significant part of COREC, was found in the density fraction 1.0–1.6 g cm − 3 except for (macro)charcoal that occurs in the lightest fraction ( − 3 ). The properties of this latter density fraction seemed to be well related to vegetation characteristics. The dichromate oxidation procedure, however, has methodological restrictions. This procedure resulted here to be poorly specific for PyOM in the investigated soils, since it isolated a fraction rich in lipids. The lack of specificity for PyOM is most likely due to the rather low content of aromatics in SOM, although fire frequency was relatively high.

Current climatic conditions and the occurrence of discontinuous and sporadic permafrost in the Alps result in a low turnover rate and therefore accumulation of organic matter (OM) in soils. Alpine soils are thus highly sensitive to global warming that potentially promotes the mineralisation of soil organic matter (SOM). This process might increase the release of CO2 to the atmosphere. Our aim was to investigate the potential effect of permafrost thawing by the analysis of the physical–chemical soil properties of permafrost versus non-permafrost sites. Specifically, we i) quantified the SOM stocks at such sites, ii) characterised SOM and its physical and chemical fractions and iii) estimated the age range of the bulk soil and stable C-fraction (radiocarbon dating). In south-eastern Switzerland, two areas above the timberline and one below the timberline (where isolated permafrost was verified) were investigated in detail. At each site, the experimental set-up consisted in the comparison of nearby soils that were either influenced or not by permafrost. The C-stocks (down to the C horizon or rock surface) did not show a significant difference between permafrost and non-permafrost soils and were in the same range of 10–15 kg/m2 in alpine (grassland) and subalpine (forest) sites. Above the timberline, the bulk SOM showed a distinct higher age at permafrost sites compared to non-permafrost sites. This higher age was even more evident in the stable C-fraction (resistant to an H2O2 treatment), where ages of up to 11 ky in permafrost soils were recorded. The highest age obtained in the stable C-fraction in non-permafrost soils was around 4 ky. Consequently, climatic conditions and the occurrence of discontinuous permafrost resulted in a very low turnover rate of SOM. At the subalpine site, the difference between permafrost and non-permafrost sites was less. At both sites (alpine and subalpine), DRIFT (Diffuse Reflection Infrared Fourier Transform) was used to determine the functional groups in the bulk soil and in the stable C-fraction. In general, the stable C-fraction had a different composition compared to the bulk SOM at non-permafrost sites; this was mostly not the case at the permafrost sites. This confirms that different decomposition processes occur between permafrost and non-permafrost sites. Furthermore, permafrost sites accumulated more the low-density physical fractions of SOM that are potentially easily degradable. The obtained results suggest that a warmer climate may not necessarily lead to an increased CO2 release from SOM-degradation in permafrost soils compared to non-permafrost soils. High-alpine soils and OM furthermore integrate a multi-facetted response to the past and ongoing surrounding conditions. The melting of permafrost will most likely enhance vegetation growth, which to a certain degree will probably compensate for carbon losses on the long-term.

As a consequence of global warming, additional areas will become ice-free and subject to weathering and soil formation. The most evident soil changes in the Alps will occur in proglacial areas where young soils will continuously develop due to glacier retreat. Little is known about the initial stages of weathering and soil formation, i.e. during the first decades of soil genesis. In this study, we investigated clay minerals formation during a time span 0–150 years in the proglacial area of Morteratsch (Swiss Alps). The soils developed on granitic till and were Lithic Leptosols. Mineralogical measurements of the clay ( The detected clay mineral formation and transformation mechanisms within this short time span confirmed the high reactivity of freshly exposed sediments, even in a cryic environment.

International audience; The older forest type Quercetum–Betuletum (oak/birch; Q-type vegetation) in southern Switzerland and northern Italy was to a large extent replaced by chestnut forests (Castanea sativa; C-type vegetation) in roman times. When laurophylloid vegetation (L-type vegetation) invaded some of these chestnut systems during the last few decades, it caused detectable changes in organic chemistry. The invasion of the L-type vegetation was predominately due to increased winter temperatures. We tested whether these vegetation changes led to measurable long-term and short-term responses of the mineral matrix by comparing soils under Q-type with C-type vegetation (probing for long-term effects; > 100–2000 years) and soils under C-type with L-type vegetation (short-term effects; a few decades). To do so, we examined soil characteristics including the dithionite-, oxalate- and pyrophosphate-extractable forms of Fe, Al and Si as well as the phyllosilicate mineralogy of the clay fraction with a pair-wise comparison procedure.On L-type patches, short-term changes resulted in higher contents of secondary, poorly crystalline Fe. The accumulation of pedogenetic Fe probably results from a lower availability of organic complexing moieties under L-type vegetation and thus leading to a reduced removal. As soil acidity did not change with the vegetation types, a strong effect of organic compounds on Fe and Al chemistry must be assumed. A correlation analysis confirmed that metal binding to organic matter was different between L-type stands (correlation of Fe and Al with organic matter was less significant) and C-type stands. The differences in clay phyllosilicate assemblage between the different vegetation sites were rather small. There was, however, a trend towards higher contents of hydroxy-interlayered vermiculite (HIV) under L-type vegetation when compared to C-type sites. It seems that Al-polymers fixation in interlayers of 2:1 clay minerals was increased or their removal hindered at sites having L-type vegetation. Changes in the long-term (response to C-type vegetation) were only measurable for the pyrophosphate-extractable Si content (formation of phytolithe?). The colonisation of laurophyllous species led in the short-term to significant alterations of the soil system that were even more pronounced than the long-term effect of chestnut on soil quality.

Two soil profile sequences on paragneiss debris in the Val di Rabbi (Northern Italy) along an altitude gradient ranging from 1200 to 2400 m a.s.l. were studied to evaluate the effect of aspect on the weathering of clay minerals. All the soils had a coarse structure, a sandy texture and a low pH. Greater weathering intensities of clay-sized phyllosilicates (greater content of smectites) were observed in soils on the north-facing slope. On the south-facing slope, smectite was found only in the surface horizon of the soil profile at the highest altitude. Hot citrate treatment of north-facing soils revealed the presence of low-charged 2:1 clay minerals, the expansion of which was hindered in the untreated state by interlayered polymers. However, the hot citrate treatment encountered some problems with the samples of the south-facing soils: as confirmed by Fourier transform infrared spectroscopy, the hot citrate treatment was unable to remove all interlayer Al polymers. The 2:1 phyllosilicates were not expanded by ethylene glycol solvation in several samples, although thermogravimetric analyses indicated the presence of clay minerals with interlayer H2O. At the same time, the collapse of clay minerals to 1.0 nm following K-saturation was evident. Theoretically, this should indicate that 2:1 phyllosilicates had no evident substitution of trioctahedral cations (Mg2+, Fe2+) by dioctahedral cations (Al3+ and Fe3+). X-ray diffraction analysis of the d060 region and determination of the layer charge of clay minerals by the long-chain (C18) alkylammonium ion, however, did not confirm this. A transformation from trioctahedral to dioctahedral species was observed and low-charge clay minerals (ξ ~0.30) were identified in the surface horizons of the south-facing sites. In the south-facing soils, the podzolization process was less pronounced because of a lower water flux through the soil and probably less complexing organic molecules that would remove the interlayer polymers. Besides the eluviation process, clay minerals underwent a process of ionic substitutions in the octahedral sheet that led to the reduction of the layer charge. This process was more obvious in the north-facing sites.

Many soils in southern Switzerland have a black color, contain a large amount of soil organic matter (SOM) and seem to have some andic properties although they did not develop on volcanic parent material. We investigated three typical 'black' soils to determine the mechanisms of (clay) mineral formation and transformation. We measured total element pools as well as the dithionite-, pyrophosphate-and oxalate-extractable fractions (Fe, Al, Si). The clay fraction (

A comparison was made between two soil climosequences on north- and south-facing slopes in northern Italy to determine the influence of slope aspect on soil processes. The climosequences span an elevational gradient ranging from moderate (1200 m a.s.l.) to high alpine (2420 m a.s.l.) climate zones on surfaces having an age of about 15 000 years. The soils were investigated with respect to organic C, oxalate and dithionite extractable Fe, Al and Si, elemental losses (Ca, Mg, K, Na, Fe, Al, Si, Mn) and clay minerals. The stocks of soil org. C as well as of oxalate-extractable Fe and Al was greatest in the subalpine zone near the timberline. There are no clear differences in organic C content between the soils on north- and south-facing sites. Fe-oxalate and to a lesser extent Alo-stocks were, however, greater on north-facing sites, indicating that weathering is greater there. Eluviation and illuviation of Al and Fe within the soil profile, typical for podzolisation, was more distinctly expressed on the N slopes. The probability of ITM (Imogolite-type-material) formation in the soil seemed to be greater on south-facing sites. On the north-facing sites, element leaching was most intense in the subalpine zone close to the timberline while on the south-facing sites this was only the case for the base cations. The N slopes exhibited higher leaching of elements which generally indicates a higher weathering intensity. On south-facing sites, typical podzolisation processes were measurable only above 2000 m a.s.l. The development of smectites is also a reflection of the weathering intensity; smectite was discernible in the surface horizon at all sites on N slopes but the highest amount was detected in the sub-alpine climate zone. For the south-facing sites only in the alpine climate zone could smectite be detected. Higher temperatures and an increased number of freeze-thaw cycles on south-facing slopes should theoretically enhance rates of chemical weathering. This could, however, not be confirmed with our measurements. The degree of chemical weathering increases from the south- to the north-facing sites that are characterised by lower temperatures, lower evapotranspiration and consequently by a higher humidity. Although precipitation in Alpine regions is abundant, the availability and flux of water through the soil is the prime factor in weathering intensity.