Comparative resource-use efficiencies and growth of Populus trichocarpa and Populus balsamifera under glasshouse conditions

Abstract

Amongst other traits, ideal poplar genotypes for afforestation programs would be fast growing and have high resource-use efficiencies. Black cottonwood (Populus trichocarpa Torr. & A. Gray) and balsam poplar (Populus balsamifera L.) are closely related species that together extend over much of the forested area of Canada. Within their respective ranges, however, black cottonwood attains much greater size than balsam poplar. Two populations of each species, each with three replicates of 9–10 genotypes, were grown from stem cuttings for 60 days in a greenhouse under long days to examine variation in biomass, height growth, net photosynthesis (A), stomatal conductance (gs), intrinsic water-use efficiency (A/gs), photosynthetic nitrogen-use efficiency (PNUE), leaf and stemwood 13C/12C isotope ratios (δ13C), stomatal density (Ds), and leaf amphistomaticity. There were no significant differences in A, PNUE, biomass, or height growth between species. On average, black cottonwood had lower gs and Ds, but higher A/gs and δ13C. Variation within provenances, in most traits, exceeded variation between species or provenances. δ13C and A/gs were highly correlated across all genotypes. Variation in A/gs seemed primarily related to gs, although positive correlations were found between δ13C and A in the P. balsamifera populations, which more generally met expectations for sink-driven differences in water-use efficiency. There is potential to identify fast-growing genotypes with relatively high use efficiencies for both water and nitrogen.