Hidden soils and their carbon stocks at high-elevation in the European Alps (North-West Italy)

Alpine soils store large quantities of total organic carbon (TOC). Given their high sensitivity to climate change, they may release large amounts of CO2 in a warming climate scenario. Thus, it is important to know their C stocks in order to estimate its possible release. While C stocks of forest, dwarf shrub and alpine grassland soils are well documented, little is known about soils and C stocks in high-elevated periglacial environments dominated by frost-driven processes. The object of this study is the periglacial environment of the Stolenberg Plateau (LTER site Istituto Mosso, 3030 m a.s.l.), at the foot of the Monte Rosa Massif (NW Italian Alps). The plateau is mostly covered by a thick stony layer, organized in periglacial blockfields and blockstreams. The plant cover reaches only 3–5%. During the construction of a chair lift, open trenches revealed, unexpectedly, well-developed soils under the active periglacial stone cover. In particular, thick (30–65 cm) and dark TOC-rich A horizons were observed. Below these Umbric horizons, Cambic Bw ones were developed but discontinuous. Despite the lack of vegetation, C stocks were remarkably high (up to ~ 5 kg m−2), comparable to vegetated soils at lower elevation. Non-invasive geophysical methods revealed that these hidden soils were widespread on the plateau under the stony cover, with a mean thickness of around 50 cm. These TOC-rich soils, without vegetation and covered by periglacial landforms, represent a unique pedoenvironment suggesting new perspectives on the actual C-stocks at high-elevation sites, which are probably underestimated.