Regional Mountain Conference

This study reports a comparative investigation of two alpine research sites situated in the Aosta Valley (Italian Alps), representing distinct neighbouring ecosystems: a high-altitude grassland and a mature larch forest. Eddy covariance flux measurements have been operational since 2008 at the grassland site (2168 m a.s.l.) and since 2012 at the larch forest site (2100 m a.s.l.). Each station is fully instrumented for flux and meteorological observations using identical instrumentation. The straight-line distance between the two sites is approximately 2.7 km and they experience comparable climatic conditions, thereby enabling direct inter-site comparisons. The primary aim of this study is to quantify and interpret differences in the carbon dioxide exchange between these ecosystems, with particular attention to the peculiarities of the years showing extreme meteorological conditions. The two sites represent contrasting stages along a land‑use transition gradient, where the abandoned grasslands — no longer subject to livestock grazing since 2008, when the area was fenced and permanently excluded from grazing — exhibit a progressive encroachment by woody
species, ultimately evolving into mature larch stands. This is a widely documented process in the Alpine region: the abandonment of traditional grazing practices and the subsequent natural recolonization of former grasslands by forest species. To complement this analysis, preliminary results from a third eddy covariance station, installed in 2024 within a transitional ecotone characterized by scattered small larch saplings and shrub
species, will also be presented. Overall, this study demonstrates how multi-year eddy covariance measurements can reveal differences in ecosystem functioning under the same climatic conditions but across distinct vegetation types and successional stages, offering new insights into carbon flux dynamics along alpine land-use gradients.