POTENTIAL IMPACTS OF ELEVATED CO2 AND ABOVEGROUND AND BELOWGROUND LITTER QUALITY OF A TALLGRASS PRAIRIE

Increased atmospheric CO2 will likely impact the productivity of arid and semiarid ecosystems through increased C, N, and water use efficiencies at the individual plant level. Tallgrass prairie has had increased above- and belowground biomass production under elevated CO2, primarily due to increased water use efficiency. There is an apparent decreased N requirement to sustain increased productivity in CO2-enriched tallgrass prairie, and C:N ratios of plant litter above and below ground have increased. The tallgrass prairie ecosystem level response to elevated CO2 on the C cycle could potentially increase C storage. Reduced litter quality associated with elevated CO2 in tallgrass prairie has the potential to reduce decomposition rates, and ruminant digestion rate of plant biomass apparently has been lowered. Reduced intake by ruminants would shunt more of the plant biomass directly into the detrital food chain, thereby slowing decomposition further. The potential impact is for increased C to be retained as soil organic matter in the tallgrass prairie.