Tree species identity and short-term weather history jointly control water repellency and infiltration in the humus-mineral soil horizon

Tree species can exert strong and species-specific controls on water infiltration in forest soils. However, the magnitude and meteorological sensitivity of these effects remain poorly quantified under standardised site conditions. We measured unsaturated hydraulic conductivity (K) and soil water repellency index (R) in the A horizon beneath seven single-species stands – lime (Tilia cordata), sycamore (Acer pseudoplatanus), maple (Acer platanoides), beech (Fagus sylvatica), oak (Quercus robur), larch (Larix decidua), and Douglas-fir (Pseudotsuga menziesii) – in a common-garden experiment on sandy Dystric Gleyic Cambisols. Measurements were conducted in five campaigns representing contrasting 10-day antecedent weather conditions. Broadleaved species such as lime, maple, and sycamore maintained low repellency and high K regardless of preceding weather, indicating low susceptibility to hydrophobicity. In contrast, conifers (Douglas-fir and larch) rapidly developed strong repellency and sharply reduced infiltration following dry spells. Beech and oak showed intermediate responses, with repellency emerging under drought but receding after wet periods. These patterns reveal that species differ not only in baseline hydraulic properties but also in the speed and magnitude of their response to short-term meteorological variability. Our study highlights the importance of species-specific functional traits in regulating soil hydraulic behaviour. Selecting species that sustain infiltration and resist the onset of hydrophobicity could help improve water retention, limit runoff, and enhance forest resilience under projected increases in drought frequency.