The research focuses on investigating how climatic and socio-economic shifts drive woody species encroachment into mountain grasslands, altering carbon sequestration patterns and contributing to ecosystem changes.
In recent decades, the Aosta Valley region has experienced a transition towards the abandonment of traditional livestock grazing activities below the forest line (~1500 meters asl). In this context, our study aims to improve knowledge about this process and the consequences of woody species encroachment in the Alps. The regeneration of shrub and tree vegetation in this mountainous landscape is closely linked to climate change and its extremes, making it challenging to disentangle their effects from those of land use change. This process offers valuable insights into how ecosystems evolve as they gradually return to a state less influenced by human activity. The activities were carried out at the ICOS-associated site Torgnon (IT-Tor), an abandoned subalpine pasture dominated by Nardus stricta, located in the Aosta Valley region at approximately 2100 m asl. Within this pasture, an area of 15,000 square meters undergoing recolonization by larches (Larix decidua) and shrubs was selected. Since 2015, periodic surveys (2015, 2018, 2021, and 2024) have been conducted to monitor vegetation dynamics. Using a GNSS system, we mapped larch tree locations, measured trunk diameters, heights, and crown dimensions, and documented associated shrub growth. Additionally, UAV aerial images have been collected annually to track landscape changes. Moreover, continuous measurements of CO2 and water fluxes, along with meteorological variables, have been available at the site since 2008. To further evaluate ecosystem fluxes, an additional eddy covariance station was installed in October 2024 in the encroached area, and preliminary flux measurements will be presented. Overall, results highlight a progressive shift from grassland to woody vegetation, influencing carbon and water dynamics. This research underscores the critical role of land cover and land use (LCLU) changes in shaping present and future global vegetation dynamics and carbon sinks, emphasizing the need to integrate these dynamics into ecosystem carbon cycle modeling.