Xylem hydraulic safety and efficiency in relation to leaf and wood traits in three temperate Acer species differing in habitat preferences

Abstract

For three widespread European Acer species with different climate envelopes, hydraulic traits, but not wood anatomical or leaf morphological traits, were good indicators for habitat preferences. Prediction of drought impacts on trees requires knowledge about species differences in hydraulic traits and how the hydraulic constitution changes along water availability gradients. We studied co-occurring mature trees of three widespread European Acer species with different climate envelopes and habitat preferences for branch hydraulic (embolism resistance, hydraulic conductivity), wood anatomical (vessel diameter, vessel density, wood density) and leaf functional traits (specific leaf area, sapwood-to-leaf area ratio, foliar δ13C), and branch growth rate. Study objectives were to examine the relation between hydraulic traits and the species’ habitat preferences and to confirm several commonly anticipated trade-offs in hydraulic traits at the genus level. The species’ habitat preferences were reflected in the hydraulic traits, but not in the studied wood anatomical or leaf traits. Embolism resistance (P12, P50 and P88 values) decreased and pit conductivity (potential minus measured conductivity) increased in the sequence A. campestre–A. platanoides–A. pseudoplatanus in parallel with the species’ putative drought tolerance. As expected, a trade-off was found between branch hydraulic efficiency and safety. Wood density was related to hydraulic safety, but neither to hydraulic efficiency nor other wood anatomical traits including vessel diameter. Branch growth rate was unrelated to wood density, but linked to vessel diameter and hydraulic conductivity. The findings from the three maple species suggest that hydraulic traits may be under stronger genetic control than leaf and wood anatomical traits that exhibited a more plastic response to the environment. The former are thus better indicators of habitat preferences.