Effects of CO 2 enrichment on growth of Liquidambar styraciflua and Pinus taeda seedlings under different irradiance levels

Mathematical growth analysis techniques were used to assess the effects of atmospheric carbon dioxide enrichment on growth and biomass partitioning of Liquidambarstyraciflua L. (sweetgum) and Pinustaeda L. (loblolly pine) seedlings. Plants were grown from seed under high (1000 μmol•m −2 •s −1 ) and low (250 μmol•m −2 •s −1 ) photosynthetic photon flux density at CO 2 concentrations of 350, 675, and 1000 μL•L −1 for 84 or 112–113 days. Elevated atmospheric CO 2 concentration significantly increased height, leaf area, basal stem diameter, and total dry weight of sweetgum seedlings grown under high irradiance and to a lesser extent under low irradiance. Increases in dry matter accumulation were associated with early CO 2 enhancement of net assimilation rate, but increases in amount of leaf surface area contributed more towards maintenance of larger size as seedlings aged. For sweetgum seedlings in particular, reduction of growth by low irradiance under normal atmospheric CO 2 was compensated for by growing plants with elevated CO 2 . In contrast, elevated CO 2 concentration produced no significant increase in growth of loblolly pine seedlings.