Regional Mountain Conference

Austria is experiencing rapid climate warming, with particularly pronounced impacts in mountain regions. Rising temperatures and altered precipitation regimes are increasing the frequency and severity of droughts, thereby placing additional stress on mountain vegetation. Reliable monitoring of vegetation phenology under these changing conditions requires high-resolution, accurate, and spatially consistent datasets that are well suited to complex alpine terrain.

Satellite remote sensing provides an effective means to monitor vegetation dynamics at regional to continental scales. Multispectral observations from the Copernicus Sentinel-2 mission are widely used for this purpose. In particular, the High Resolution Vegetation Phenology and Productivity (HR-VPP) product delivers 10-daily vegetation indices as well as annual indicators of phenological timing (e.g. start and end of season) and vegetation productivity.

More recently, synthetic aperture radar (SAR) observations have emerged as a promising complementary approach for monitoring vegetation dynamics. Radar backscatter is sensitive to vegetation structure and water content and can provide valuable information independent of cloud cover. The C-band SAR sensor onboard Sentinel-1 has demonstrated sensitivity to vegetation dynamics and soil moisture, while the L-band SAR observations from the Argentinian SAOCOM mission are particularly responsive to woody vegetation components. Together, Sentinel-1 and SAOCOM data have the potential to complement optical Sentinel-2 observations.

However, the application of SAR-based vegetation monitoring in mountainous regions remains challenging due to the strong influence of snow cover and complex terrain on radar backscatter. Here, we present preliminary results on the retrieval of vegetation dynamics and phenological metrics from Sentinel-1 and SAOCOM SAR observations across selected study sites in Austria. Vegetation information derived from Sentinel-1, Sentinel-2, and SAOCOM is intercompared to assess synergies, differences, and limitations. Particular emphasis is placed on the mountainous Long-Term Ecological Research (LTER) site Zöbelboden in the Kalkalpen region, where an extensive set of in situ measurements is available for validation.