Monitoring soil erosion and vegetation pattern related to microclimatic conditions in Icelandic and Fennoscandian tundra

The Arctic tundra, a key regulator of the global carbon cycle that stores nearly half of the world's below-ground organic carbon, is increasingly threatened by soil erosion driven by climate change and anthropogenic activity. Topography moderates these impacts on small spatial scales by creating microclimates that shape biogeomorphological processes and the distribution of barren and vegetated areas. Seasonal variations further influence these dynamics, adding to the complexity of monitoring and assessing landscape resilience under growing environmental pressures. This research addresses two key questions: How can we best monitor tundra environments? Where and how will different tundra environments respond to changing climatic conditions? Fieldwork was conducted in Svalbarðshreppur, Iceland and Kilpisjärvi, Finland during the growing seasons of 2021-2023. Methods included remote sensing data from multispectral uncrewed aerial vehicle (UAV) surveys, optical satellites (Landsat, Sentinel-2, PlanetScope) and digital elevation models derived from UAV, aerial LiDAR (light detection and ranging) and ArcticDEM. Soil moisture and temperature sensors were deployed along mesotopographic transects, together with vegetation surveys, to provide ground-level information. Findings revealed limitations of common satellite systems for soil erosion monitoring due to spectral confusion caused by shrub expansion. The Shannon Evenness Index was introduced to identify suitable spatial resolutions for environmental monitoring, revealing that a resolution of <3 m is necessary in Iceland to minimise excessive mixed pixels. Seasonal microclimatic conditions and topographic position influenced the distribution of land cover and plant structure. In summer, soil moisture impacted plant species richness and distribution, with increased water stress observed on ridge positions. In winter, snow cover duration (SCD), associated with thermal insulation and wind protection, was a determining factor on the distribution of barren and vegetated areas. In Finland, an SCD of approximately 155 days was identified as a tipping point, beyond which snow cover shifts from benefiting vegetation to suppressing it.