Responses of Gmelina arborea, a tropical deciduous tree species, to elevated atmospheric CO2: Growth, biomass productivity and carbon sequestration efficacy

Abstract

The photosynthetic response of trees to rising CO 2 concentrations largely depends on source-sink relations, in addition to differences in responsiveness by species, genotype, and functional group. Previous studies on elevated CO 2 responses in trees have either doubled the gas concentration ( > 700μmolmol -1) or used single large addition of CO 2 (500-600μmolmol -1). In this study, Gmelina arborea, a fast growing tropical deciduous tree species, was selected to determine the photosynthetic efficiency, growth response and overall source-sink relations under near elevated atmospheric CO 2 concentration (460μmolmol -1). Net photosynthetic rate of Gmelina was ∼30% higher in plants grown in elevated CO 2 compared with ambient CO 2-grown plants. The elevated CO 2 concentration also had significant effect on photochemical and biochemical capacities evidenced by changes in F V/F M, ABS/CSm, ET 0/CSm and RuBPcase activity. The study also revealed that elevated CO 2 conditions significantly increased absolute growth rate, above ground biomass and carbon sequestration potential in Gmelina which sequestered ∼2100gtree -1 carbon after 120 days of treatment when compared to ambient CO 2-grown plants. Our data indicate that young Gmelina could accumulate significant biomass and escape acclimatory down-regulation of photosynthesis due to high source-sink capacity even with an increase of 100μmolmol -1 CO 2. © 2011 Elsevier Ireland Ltd.