Propagation of trembling aspen and hybrid poplar for agroforestry: potential benefits of elevated CO2 in the greenhouse

摘要

We examined the usefulness of elevated CO2 in the greenhouse to aid in early selection of genotypes and in the propagation of Populus tremuloides Michaux (aspen) and hybrid poplars for agroforestry, afforestation, or reclamation. Growth in elevated (800 ppm) vs ambient (375 ppm) CO2 for 95 days resulted in greater height (14%), stem caliper (16%), overall biomass, and proportional allocation of biomass to roots as well as elevated net assimilation and water-use-efficiency. Aspen clones selected for superior growth (based on phenotypic selection) broke bud significantly earlier than unselected clones under both CO2 levels; superior clones were also taller with greater stem caliper under both CO2 treatments (but not significant). Under ambient CO2 male aspen were taller than females while under elevated CO2 female aspen were taller than males and also had greater caliper (but not significant). Hybrid poplar grown under elevated (vs ambient) CO2 broke bud significantly earlier and had significantly greater net assimilation and water-use efficiency; they were also taller with greater caliper (but not significant). Differences in performance among the eight hybrid clones were enhanced by growth under elevated CO2. Under ambient CO2, P38P38 was the clone that broke bud earliest, was tallest with greater caliper and had a lower shoot:root biomass ratio. Sargentii, on the other hand, was the shortest with the smallest caliper. The implications of these results need to be considered in the context of using aspen and hybrid poplar for large-scale agroforestry, afforestation and reclamation across Canada.