Effects of elevated CO2 and soil temperature on the growth and biomass responses of mountain maple (Acer spicatum L.) seedlings to high light environment

Background/Question/Methods

Mountain maple (Acer spicatum L.) is an important shrub or tree species in the boreal forest understory of North America. It survives and grows slowly under the forest canopy for a long period of time, but exhibits light-foraging growth habits. Some shade tolerant understory tree species such as mountain maple (Acer spicatum L.) exhibit light-foraging growth habits. Global environment change scenarios, such as elevated carbon dioxide concentration and soil warming may therefore affect mountain maple response to light environment. In this study, we sought to examine the effects of elevated carbon dioxide concentration and soil warming on the growth and biomass responses of mountain maple seedlings to increases in light availability. We investigated how elevated [CO₂] and soil warming influence the growth and biomass responses of mountain maple seedlings to light availability. We hypothesized that elevated carbon dioxide concentration and soil warming would cause greater enhancement of growth and biomass of mountain maple seedling growing in high light environment. To test this hypothesis, we exposed the seedlings to: a) two levels of light (100% of greenhouse light and 30%); b) two carbon dioxide concentration (ambient or 392 µmol mol^-1 and elevated or 784 µmol mol^-1); and c) two soil temperature regimes (17°C and 22°C). We measured seedlings growth and biomass after one growing season. 

Results/Conclusions

We found that under ambient [CO₂], the higher light level increased seedlings height increased by 70% and 56% at low T_soil and high T_soil, respectively. Under the elevated [CO₂], however, the high light level increased seedlings height by 52% and just 13% at low T_soil high T_soil, respectively. Seedlings biomass generally followed the aboveground growth response patterns to light under [CO₂] and T_soil: the degree of biomass response to light was lowest under the elevated [CO₂] and warmer T_soil. Thus, elevated [CO₂] and soil warming may have little influence on mountain maple seedlings establishment in canopy gaps in the future.