The influence of elevated carbon dioxide and water availability on herbaceous weed development and growth of transplanted loblolly pine (Pinus taeda).
Loblolly pine (Pinus taeda L.) seedlings were grown in competition with native weeds using soil and seed bank collected from recently chopped and burned areas near Appomattox, Virginia. One-year-old seedlings were planted and weeds allowed to germinate from the native seed bank while being exposed to CO(2) (ambient and elevated - approximately 700 ppm) and water (water stressed and well watered) treatments for approximately one growing season in a greenhouse. Elevated CO(2) did not influence total weed biomass; however, C(3) weed community development was favored over C(4) weed community development in elevated CO(2) regardless of water availability. This suggests that weed community composition may shift toward C(3) plants in a future elevated CO(2) atmosphere. Pine growth was significantly greater in the well watered and elevated CO(2) treatments compared to the water stressed and ambient treatments, respectively, even though they were competing with native herbaceous weeds for resources. There was a significant water and CO(2) interaction for pine root:shoot ratio. Under elevated CO(2), root:shoot ratio was significantly greater in the water stressed treatment than the well watered treatment. In contrast, there was no significant difference in the root:shoot ratio under the ambient CO(2) treatment for either water treatment. These results suggest that loblolly pine seedlings will respond favorably in an elevated CO(2) atmosphere, even under dry conditions and competing with herbaceous weeds.
Gavazzi
M
Virginia Polytechnic Institute and State University, Department of Forestry, Cheatham Hall, Room 236, 24060, Blacksburg, VA, USA
Seiler
J
Aust
W
Zedaker
S