Carbon sequestration in temperate grassland ecosystems and the influence of management, climate and elevated CO2

The substantial stocks of carbon sequestered in temperate grassland ecosystems are located largely below ground in roots and soil. Organic C in the soil is located in discrete pools, but the characteristics of these pools are still uncertain. Carbon sequestration can be determined directly by measuring changes in C pools, indirectly by using C-13 as a tracer, or by simulation modelling. All these methods have their limitations, but long-term estimates rely almost exclusively on modelling. Measured and modelled rates of C sequestration range from 0 to > 8 Mg C ha(-1) yr(-1). Management practices, climate and elevated CO2 strongly influence C sequestration rates and their influence on future C stocks in grassland soils is considered. Currently there is significant potential to increase C sequestration in temperate grassland systems by changes in management, but climate change and increasing CO2 concentrations in future will also have significant impacts. Global warming may negate any storage stimulated by changed management and elevated CO2, although there is increasing evidence that the reverse could be the case.