Fabio Oriani, Helge Aasen, Manuel K. Schneider

An accurate long-term monitoring of mountain rangelands is of primary importance for biodiversity conservation and sustainability of pastoral land use. In this study, we investigate how the seasonality of growth in nine habitats composing the alpine rangeland ecosystem responds to differences in weather conditions from year to year and how these changes occur along the elevation profile. We apply a novel pixel-based analysis over an area of 1000 km² in mid-to-high elevation pastures surrounding the Swiss National Park (south-eastern Swiss Alps). By means of NDVI, we track the growth of different habitats across the period 2016-2023. The results suggest that wet and mesic pastures tend to grow more than dry units in an elevation range of 2000-2400 m a.s.l, while all habitats present a similar growth above 2400 m. Moreover, while growth in the first season half is strongly controlled by snow persistence, it is in part compensated by very fast growth after late-melting snow. Conversely, in the second half season, the growth pattern is limited by the arrival of snow in autumn, very abruptly in tall shrubs. Inter-annual weather fluctuations impact equally the habitats and more in the first half of the growth season. This workflow presents as an effective strategy to monitor the seasonal and long-term evolution of mountain rangeland vegetation in the complex alpine domain.