What influences alpine pasture productivity? Exploring the relation among topography, climate, and biomass using remote sensing.

Mountain pastures are a biodiversity rich and heterogeneous ecosystem of the Alps influenced by a complex topography and a variable climate. Understanding the impact of these factors on pasture productivity is of primary importance for forage production and ecosystem preservation.

We present here a regional analysis covering the alpine pastures in the Grisons Canton (eastern Switzerland, 1997 sq. km), for which we developed a collection of high-resolution (10-m) annual growth indicators based on the Enhanced Vegetation Index (EVI) derived from Sentinel-2 images, from 2016 to 2024. We correlate our growth maps to a 1-km gridded climate dataset (Meteoswiss) and a 10-m digital elevation model (Swisstopo) to understand which weather factors - rainfall, temperature, or radiation - influence the most the growing season and from which period of the year. In addition, we explore the variability of these dependencies in space, in relation to elevation and derived topographic descriptors, e.g. slope or valley orientation.

This analysis shades light on the climate dynamics impacting the most the growing season in conjunction to a complex local topography. The results can be used to identify vulnerability levels along the elevation profile, influenced by soil depth and valley orientation, where growth varies the most from year to year in function of annual weather variations. In these zones, pasture management will need extra flexibility measures and real-time monitoring to adapt to annual fluctuations of a future climate change.