How diverse are Populus “diversifolia” leaves? Linking leaf morphology to ecophysiological and stand variables along water supply and salinity gradients

•Specific leaf area (SLA) correlated negatively with water use efficiency (δ13C).•Correlations between SLA and leaf morphology were significant, but weak.•SLA was positively related to tree height, wood production and stand density.•Na+ reduced leaf conductance (inferred from δ18O), but not biomass production.•SLA provides acclimatization to water supply and local transpirational demand.