Elevated CO2 enhances the growth of hybrid larch F1 (Larix gmelinii var. japonica x L-kaempferi) seedlings and changes its biomass allocation

Elevated CO (2) enhances the photosynthesis and growth of hybrid larch F (1) seedlings. However, elevated CO (2) -induced change of tree shape may have risk to the other environmental stresses. The hybrid larch F-1 (Larix gmelinii var. japonica x L. kaempferi) is one of the most promising species for timber production as well as absorption of atmospheric CO2. To assess the ability of this species in the future high CO2 environment, we investigated the growth and photosynthetic response of hybrid larch F-1 seedlings to elevated CO2 concentration. Three-year-old seedlings of hybrid larch F-1 were grown on fertile brown forest soil or infertile volcanic ash soil, and exposed to 500 mu mol mol(-1) CO2 in a free-air CO2 enrichment system located in northern Japan for two growing seasons. Regardless of soil type, the exposure to elevated CO2 did not affect photosynthetic traits in the first and second growing seasons; a higher net photosynthetic rate was maintained under elevated CO2. Growth of the seedlings under elevated CO2 was greater than that under ambient CO2. We found that elevated CO2 induced a change in the shape of seedlings: small roots, slender-shaped stems and long-shoots. These results suggest that elevated CO2 stimulates the growth of hybrid larch F-1, although the change in tree shape may increase the risk of other stresses, such as strong winds, heavy snow, and nutrient deficiency.