Forest ecosystems interact strongly with hydrological processes across a wide range of spatial and temporal scales. Their interactions with soils, groundwater and topography, together with often extensive root systems, create complex pathways for water movement through forest ecosystems. These include the interception, storage and redistribution of water in forest canopies before it reaches the soil, the infiltration and redistribution of water in the soil and subsurface, interactions with groundwater, and the uptake of water by roots and its subsequent transport to the atmosphere. Understanding these often-hidden connections is essential for quantifying forest water use and the role of forests in the water cycle.

Our ability to detect these processes is expanding through new approaches, including geochemical and isotopic tracers, geophysical and remote sensing techniques, high-resolution measurements and process-based modelling. These approaches provide new and sometimes surprising perspectives on water fluxes in forested ecosystems. The exceptional drought and heat experienced across large parts of Europe in 2026 further highlight the importance of understanding how forests access, redistribute and use water.

This session welcomes contributions that provide new insights into forest ecohydrological processes or demonstrate novel approaches to observing and modelling water fluxes in forest ecosystems. We particularly invite studies addressing how forest canopies modify water availability and fluxes, including interception, throughfall and stemflow; water movement through the soil and subsurface; root water uptake and water sources; and the transport and use of water within trees, as well as forest water stress, drought responses, and the links between forest hydrological processes and the water, carbon and nutrient cycles.