Leaf hydraulic distance is a good predictor of growth response to climate aridity within and across conifer species in a Taiga ecosystem

Despite inter-specific differences in hydraulic traits at broad scale have been comprehensively studied, intra-specific hydraulic variability in situ is less well known. Which hydraulic traits can better predict whole-plant performance in field both within and across species remains largely ambiguous. In the study, we conducted a field investigation on branch radial growth, leaf and branch anatomical traits related to hydraulics, as well as leaf pressure–volume curve parameters of two dominant conifer species (Larix sibirica and Picea obovata) at four sites over an aridity gradient across the Altay Mountain range, which locates at the southern edge of Taiga ecosystem, one of the largest and the most sensitive terrestrial biomes to climate change. L. sibirica is a generalist deciduous conifer species, while P. obovata is a specialist evergreen conifer species. It was found that: 1) P. obovata showed ten times higher slope of branch radial growth (RGRbranch) fitted to aridity than L. sibirica; 2) the hydraulic distance from the bundle sheath to the stomata (DMC) can predict the growth rate both within and across species; 3) earlywood and latewood anatomies showed different relations to RGRbranch within and across species; 4) leaf saturated osmotic potential (Ψsat) but not turgor loss osmotic potential (Ψtlp) was significantly and positively related to RGRbranch within species. Our results support the hypothesis that specialists are more sensitive in growth to climate change than generalists. Further, the results highlight DMC as a pivotal role in water transport and associated carbon assimilation both within and across species in Taiga ecosystem, therefore at the core of the structural adjustments to climate change in this largest and the most sensitive terrestrial biome.