Spatial-temporal redistribution of seasonal precipitation and stable water isotopes in a boreal coniferous forest

Boreal forest hydrological processes can be strongly influenced by the pronounced seasonality of precipitation, yet the spatiotemporal redistribution of rainfall and snowfall within forest canopies remains insufficiently understood. We investigate precipitation redistribution in a northern boreal Scots pine forest at the Oulanka station, Finland, with a focus on characterizing and quantifying seasonal variability and the spatial distribution of water inputs at the forest level and stable water isotope characterization of forest and open-area precipitation. We monitored throughfall, stemflow, snowmelt, and snowpack dynamics within the forest stand from July 2024 to April 2025. This integrated forest observational framework allows us to assess how canopy interception, rain-snow redistribution, and snowpack processes jointly regulate water inputs and its isotope composition to the forest floor across seasons. Preliminary analyses reveal strong seasonal differences in precipitation redistribution. Initial isotope observations suggest limited modification of precipitation isotopic signatures by canopy processes, indicating that physical redistribution rather than isotopic fractionation plays a dominant role in canopy-precipitation interactions in this forest. Our study provides new insights into the seasonal water inputs of boreal forest ecohydrology and contributes to improving process-based representations of forest ecohydrology in cold-regions and tracer-aided models, with potential benefits for local water resource management and the forestry sector.