Different growth response of mountain rangeland habitats to inter-annual weather fluctuations

Abstract

Monitoring mountain rangelands is crucial for ensuring the sustainability of pastoral land use. In this study, we employ satellite image analysis to investigate how the seasonal growth patterns in the mountain rangeland ecosystem respond to inter-annual variations in weather conditions along the elevation profile. Our analysis covers nine key habitats in mountain rangelands surrounding the Swiss National Park, southeastern Swiss Alps from 2000 to 2800 m of elevation. Using the Normalized Difference Vegetation Index (NDVI) to track the growth pattern from 2016 to 2023 reveals that inter-annual weather fluctuations affect all habitats, leading to variations of 15–20% in the growth curve, with more significant impacts observed in the first half of the growing season. When comparing growth among habitats, wet and mesic pastures tend to exhibit greater growth compared to dry habitats within the elevation range of 2000–2400 m above sea level, while all habitats show a similar growth above 2400 m. Additionally, the presented statistical analysis at the landscape scale supports the existence of growth dynamics previously observed at the plot scale: that snow persistence influences the beginning of growth in pastures, but this effect is partially compensated by rapid growth following late snow melt. Conversely, in the second half of the season, growth is controlled by the onset of snow in autumn. These results demonstrate the potential of the joint application of earth observation and spatial statistics, not only to monitor the regional response to climate trends and variability, but also to differentiate inter-annual and inter-habitat responses of growth dynamics.