Depicting vegetation dynamics along the Tagliamento river bars: a remote sensing approach to monitor biodiversity in alpine rivers

Rivers play a critical role in biodiversity conservation and ecological connectivity. Understanding how plant communities vary in these dynamic systems and how their changes are visible using remote sensing is crucial for implementing effective conservation strategies. The Tagliamento river (N-E Italy) is characterized by flood events and a wide pristine gravel-bed where river bars are characterized by complex habitats corresponding to different successional stages. It is therefore subjected to nature conservation initiatives. In this area, 51 plots of 100 m2 area have been sampled during 2022 and 2023 seasons, within an Erasmus+ program involving four European countries. In each plot we performed vegetation surveys and collected soil data. Moreover, we analysed satellite images back to the 1980s to calculate principal multispectral indices and the age of the river bars. We found satellite-derived indices very effective in tracing changes of vegetation over time. NDVI was strongly positively related to the river bars age. Moreover, the plant functional diversity of the community appears to be driven by the river bars age, and linked to the NDVI. Our results provide new insights into the dynamics of riverbed vegetation and the application of satellite imagery for remote sensing and conservation of these valuable habitats.