Scale Matters: Disentangling Carbon–Water Coupling from Leaves to Ecosystems

This dataset provides long-term simulations of carbon and water flux dynamics, including Gross Primary Production (GPP), Evapotranspiration (ET), intrinsic Water Use Efficiency (iWUE), and ecosystem-scale Water Use Efficiency (WUEeco) for Fagus sylvatica at the Lägeren site (CH-Lae), Switzerland for the period 2004-2023 at daily scale. Simulations were performed using the 3D-CMCC-FEM (Three Dimensional - Coupled Model Carbon Cycle - Forest Ecosystem Module) (Collalti et al., 2016; 2020; 2024; Dalmonech et al., 2022; 2024; Puchi et al., 2026; Saponaro et al., 2025a; 2025b), a biogeochemical, biophysical, and eco-physiological process-based model specifically designed to simulate carbon and water cycle dynamics in forest ecosystems across daily, monthly, and annual timescales. The model has been extensively validated across multiple species and climatic gradients within internationally recognized monitoring networks, including FLUXNET, ICOS, and PROFOUND (Marconi et al., 2017; Reyer et al., 2020; Mahnken et al., 2022).