Crown-Scale Surface Sealing Is Associated with Leaf and Seed-Hair Traits of Female Populus tomentosa: Implications for Sustainable Landscape-Site Management

Impervious surfaces create heterogeneous planting sites for urban trees, but whether crown-scale sealing is associated jointly with leaf economics and reproductive dispersal morphology remains unclear. We aimed to test these associations in mature female Populus tomentosa while treating impervious surface area (ISA) as a composite indicator of site context rather than a direct measure of thermal or hydrological stress. In a single-season, cross-sectional survey of 180 trees in Beijing (60 per low-, mid-, and high-ISA descriptive stratum), we measured crown-scale ISA, short-term midday ground-surface temperature, a pervious-soil access-moisture index (PSAMI), eight leaf traits, and five reproductive traits, and analyzed continuous associations, group contrasts, effect sizes, and multivariate patterns. Greater ISA was associated with lower PSAMI (R2 = 0.581) and higher land surface temperature (R2 = 0.845). Compared with low-ISA trees, high-ISA trees had lower specific leaf area (117.5 ± 29.1 vs. 90.9 ± 19.0 cm2 g−1; Hedges’ g = −1.07, 95% CI [−1.50, −0.71]) and longer seed hairs (0.564 ± 0.067 vs. 0.727 ± 0.078 cm; g = 2.24, 95% CI [1.82, 2.78]), together with greater fuzz biomass and lower seed mass. Multivariate analyses showed coordinated shifts in mean leaf and reproductive phenotype without stronger within-stratum cross-module integration. We conclude that the study’s principal contribution is the joint description of vegetative economics and reproductive dispersal morphology on the same mature urban trees. Because ISA co-varied with land use and management and PSAMI includes structural zeros, the findings are preliminary and do not establish causal stress mechanisms, plant-available water status, airborne exposure, or management effects; multi-year matched-site validation is required.