Papers by Dagmar Brandova
Geomorphology, 2009
C 10 Be Clay minerals Weathering Deglaciation A combination of three relative and two absolute (n... more C 10 Be Clay minerals Weathering Deglaciation A combination of three relative and two absolute (numerical) dating techniques, applied on nine soil profiles in an Alpine environment located in Val di Rabbi (Trentino, Northern Italy), was used to improve the investigation methodology of Alpine sites in response to climate change and to reconstruct the chronology of late Pleistocene and early Holocene landscape evolution. The degree of podzolisation, clay mineral evolution and the element mass balances of each site were investigated. Furthermore, the stable fraction of the soil organic matter (SOM) was extracted with 10% H 2 O 2 and 14 C-dated. The age of the organic residues was compared with the age of charcoal fragments found in one of the studied soils and with the age of rock boulders obtained by surface exposure dating (SED) with cosmogenic 10 Be. Numerical dating and weathering characteristics of the soils showed a fairly good agreement and enabled a relative and absolute differentiation of landscape elements. The combination of 14 C-dating of SOM and SED indicated that deglaciation processes in Val di Rabbi were already far advanced by around 14 000 cal BP and that glacier oscillations affected the highest part of the region until about 9000 cal BP. The development of clay minerals is time-dependent and reflects weathering intensity. We found a close link between secondary clay minerals like smectite or vermiculite and soil age as obtained by the dating of the organic residues after the H 2 O 2 treatment. Calculated element mass balances strongly correlated with the ages derived from 14 C measurements. Old soils have lost a major part of base cations (up to 75% compared to the parent material), Fe and Al, which indicates a continuous high weathering intensity. Results of the chemical and mineralogical analyses were in good agreement with numerical dating techniques, showing the dynamics of an Alpine landscape within a relatively small area. The combination of relative and absolute dating techniques is a promising tool for the reconstruction of landscape history in high-elevation Alpine areas on siliceous substrates.
Geomorphology, 2010
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CATENA, 2013
Keywords: Alpine soils Climate Stocks of soil organic carbon Stability of soil organic carbon Rad... more Keywords: Alpine soils Climate Stocks of soil organic carbon Stability of soil organic carbon Radiocarbon dating 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 CO 2 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/m 2 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 H 2 O 2 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 CO 2 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.
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Papers by Dagmar Brandova