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Effects of elevated CO2 and competition on loblolly pine seedlings.
Osuna, Miguel*,1, Vavrek, Milan1, Campbell, William1, 1 Louisiana Tech University, Ruston, LA
ABSTRACT- The effect of elevated CO2 on a Louisiana loblolly pine system was examined. Soil, including the natural seed bank, from a recent loblolly clear-cut site was transplanted into twenty-four open top chambers. To ensure species consistency, Panicum virgatum (switchgrass), Lolium perenne (ryegrass), Amaranthus retroflexus (red root), Ambrosia artemisiifolia (ragweed), and Pinus taeda (loblolly pine) seedlings were also transplanted into each chamber. The chambers were treated with ambient (370 ppm) or elevated (760 ppm) CO2 concentrations. Preliminary results after eight months show loblolly height in open top chambers increased when exposed to elevated CO2. To test whether the height response was due to CO2 concentration or competition, loblolly pine grown under competing and non-competing conditions in growth chambers were also analyzed. Results show that pine height was greater when competing with ragweed under elevated CO2 conditions. However, pine height decreased in elevated CO2, when grown in competition with switchgrass. Thus, both competition and CO2 concentration are important in determining growth of loblolly seedlings. Understanding species interactions and regeneration of forest communities in elevated CO2 is necessary to project responses to future CO2 concentrations and to ensure future sustainable forest ecosystems.
KEY WORDS: elevated CO2, competition, loblolly pines