Decomposition and stabilisation of Norway spruce needle-derived material in Alpine soils using a 13C-labelling approach in the field
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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.
KeywordsAlps Carbon stabilisation in soils Density fractionation Exposure Labelled 13C organic matter Picea abies
This study is part of the DecAlp DACH project no. 205321L_141186 and the snf project 200021_162338. J. Ascher-Jenull has been funded by the Fonds zur Förderung der wissenschaftlichen Forschung (FWF) Austria (Project I989-B16). We are indebted to Fabio Angeli of the ‘Ufficio distrettuale forestale di Malé’ and his team of foresters for their support in the field.
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