Submitted to: Ecological Society of America Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/1999
Publication Date: N/A
Technical Abstract: Examining the effects of elevated CO2 on physiology and biochemistry of plants grown in competition will be useful for understanding how plant and ecosystem processes may change in the future. We planted five common associates representative of natural regenerating longleaf pine communities in the ground at densities reflective of nature: (1) longleaf pine, (2)wiregrass (C4), (3)sand post oak, (4)rattlebox (C3 perennial herbaceous legume), and (5)butterfly weed. Open top chambers were used to administer either ambient (360 ppm mol mol-1) or elevated CO2 (720 ppm mol mol-1) concentrations. Growth in elevated CO2 did not affect photosynthesis in wiregrass, crotalaria, and oak. Observed decreases in conductance of 14%, 43%, and 37% for these three species suggest that reductions in stomatal apertures and/or densities prohibited a positive response. Conversely, in pine, photosynthesis was enhanced by 40% while conductance was unaffected. Rubisco activity was enhanced in rattlebox (46%), oak (41%) and pine (45%) but was unaffected in wiregrass, a C4 plant. Although not present in detectable amounts in pine and oak, CO2 had no effect on phosphoenolpyruvate carboxylase in wiregrass or crotalaria. Total protein concentrations were decreased in wiregrass (32%), oak (44%), and pine (45%) but were not effected in crotalaria, a nitrogen fixer. These results will be compared to data obtained one year later in order to determine if physiological and biochemical response patterns will be maintained through time.