Elevated CO2 enhances resprouting of a tropical savanna tree

The savannas (cerrado) of south-central Brazil are currently,subjected to f requent anthropogenic burning, causing widespread reduction in tree density . Increasing concentrations of atmospheric CO2 could reduce the impact of s uch frequent burning by increasing the availability of nonstructural carboh ydrate, which is necessary for resprouting. We tested the hypotheses that e levated CO2 stimulates resprouting and accelerates replenishment of carbohy drate reserves. Using a factorial experiment, seedlings of a common Brazili an savanna tree, Keilmeyera,ern coriacea, were grown at 350 ppm and 700 ppm CO2 and at two nutrient levels. To simulate burning, the plants were eithe r clipped at 15 weeks or were left unclipped. Among unclipped plants, CO2 a nd nutrients both stimulated growth, with no significant interaction betwee n nutrient and CO2 effects. Among clipped plants, both CO2 and nutrients st imulated resprouting. However, there was a strong interaction between CO2 a nd nutrient effects, with CO2 having a significant effect only in the prese nce of high nutrient availability. Under elevated CO2, carbohydrate reserve s remained at higher levels following clipping. Root total nonstructural ca rbohydrate remained above 36% in all treatments, so carbohydrate reserves d id not limit regrowth. These results indicate that under elevated CO2 this species may be better able to endure the high frequency of anthropogenic bu rning in the Brazilian savannas.