Post-fire resprouting responses of native and exotic grasses from Cumberland Plain Woodland (Sydney, Australia) under elevated carbon dioxide

This study investigated the effect of elevated CO₂ on the post-fire resprouting response of a grassland system of perennial grass species of Cumberland Plain Woodland. Plants were grown in mixtures in natural soil in mesocosms, each containing three exotic grasses (Nassella neesiana, Chloris gayana, Eragrostis curvula) and three native grasses (Themeda australis, Microlaena stipoides, Chloris ventricosa) under elevated (700ppm) and ambient (385ppm) CO₂ conditions. Resprouting response after fire at the community- and species-level was assessed. There was no difference in community-level biomass between CO₂ treatments; however, exotic species made up a larger proportion of the community biomass under all treatments. There were species-level responses to elevated CO₂ but no significant interactions found between CO₂ and burning or plant status. Two exotic grasses (N. neesiana and E. curvula, a C₃ and a C₄ species respectively), and one native grass (M.stipoides, a C₃ species) significantly increased in biomass, and a native C4 grass (C.ventricosa) significantly decreased in biomass under elevated CO₂. These results suggest that although overall productivity of this community may not change with increases in CO₂ and fire frequency, the community composition may alter due to differential species responses.10 page(s