High-Altitude Afforestation in the Austrian Alps: Effects on Soil Organic Carbon and Microbial Communities

The warming climate and the decline in alpine pasture management are paving the way for the afforestation of currently unforested high-altitude areas. This shift holds significant potential for CO₂ sequestration in tree biomass, yet the implications for existing soil carbon stocks remain uncertain. The BERGAUF project ("Biodiversity Conservation and Carbon Storage in Forested Highlands") aims to shed light on this issue by investigating five model reforestation areas at the treeline in the Austrian Alps, established in the 1960s and 1970s.

Our primary objective is to investigate how afforestation at high-altitude areas affects vegetation and soil carbon and nitrogen stocks, plant and microbial biomass, as well vascular plant diversity, certain insect groups, and the soil microbial community structure (including bacterial and fungal biodiversity).

Here we share our initial findings on soil-related parameters, including soil carbon and nitrogen contents and stocks in the organic layer, bulk soil, and soil extracts. We also examine the quality of soil organic carbon (estimated by FTIR), soil microbial biomass and community composition, and fine root biomass, from soil samples taken at four different depths (0-10 cm, 10-20 cm, 20-40 cm, 40-60 cm). To assess the effects of afforestation, we used directly adjacent alpine meadows as control sites, which were sampled and analysed in the same manner.

We will discuss the potential of afforestation in high-altitude areas for carbon sequestration and its effects on carbon allocation and microbial biodiversity within the soil profile.