Magalie's MSc work and data Data owner: Magalie Galarneau. Email address of owner: magalie dot galarneau at gmail dot com. Data DOI: https://doi.org/10.5281/zenodo.17842837. Please do not use without prior permission. Dates of data collection: July 2023 - August 2023. SIZE Number of traits: 7, Number of species: 6, Number of treatments: 3, Number of plots: 108, Number of individuals: 972. SITE Study site: IDENT-Outaouais, Notre-Dame-de-la-Paix, Qc, Canada (45.7742, -75.0066). 108 plots containing a 7x7 assemblage of temperate trees, planted as seedlings in 2020 at regular intervals of 0.5 m. Plots contained either monocultures or three-species mixes. Three water exclusion treatments were applied to plots (a control, a pulse treatment, and a press treatment). The experiment was replicated in three blocks, such that each combination of treatment and plot composition was repeated three times. STUDY ORGANISMS The 9 central trees from each plot were measured (972 trees). Ontogenetic stage: Sapling. Size criteria: Minimum of 20 leaves fully expanded. For selection of individuals and leaves, see details in . TRAIT LIST & ASSOCIATED UNITS: Leaf Area (cm2); Leaf Mass per Area (g/cm2); Chlorophyll Concentration (mg/m2); Stomatal Density (stomata/mm2); Specific root length (m/g); Root Diameter (mm); Root Tissue Density (g/cm3). ENVIRONMENTAL VARIABLES & ASSOCIATED UNITS: Volumetric Water Content (%), Light Availability, Leaf Health. COVARIATES & ASSOCIATED UNITS: Species, Plot ID, Treatment, Block, Sampling date. SPECIES LIST: Acer saccharum, Betula alleghaniensis, Larix laricina, Picea glauca, Pinus resinosa, Quercus rubra. DATA TRANSFORMS: The data provided here have been normalized, standardized, and corrected for sampling date.