Long-term atmospheric CO₂ enrichment affects the growth and development of <i>Liquidambar</i><i>styraciflua</i> and <i>Pinus</i><i>taeda</i> seedlings

Growth and development of native species of trees in response to long-term increases in atmospheric CO 2 concentration were studied. Seedlings of two competing perennials, Pinustaeda L. and Liquidambarstyraciflua L., were obtained from germinated seeds and grown through one complete growing season at 350, 500, and 650 μL•L −1 CO 2 . The plants were grown in CO 2 controlled greenhouses under natural photoperiods and light regimes, with temperature controlled to simulate mean local climate. Stem length and basal stem diameter increased with increasing CO 2 in both species. Liquidambarstyraciflua maintained size dominance in all concentrations. The dry weights of stems, roots, and leaves increased in both species. In P. taeda, however, the seedlings reached maximum size at 500 μL•L −1 while L. styraciflua continued to increase up to 650 μL•L −1 . Liquidambarstyraciflua produced significantly more branches and leaves at the higher CO 2 concentrations than at 350 μL L −1 . Differences in plant shape and responses in growth rate of these two naturally competing tree species suggest that continuing atmospheric CO 2 enrichment could affect future interactions between the species and might produce changes in community composition.