Measuring carbon stocks across land use systems: a manual

Without ‘greenhouse gases’, planet Earth would not support life as we know it; however, the actual amount of heat trapped in the atmosphere is in a delicate balance with the climatic systems and ocean currents of the globe. Rapid increases in atmospheric CO 2 concentrations that we have witnessed over the last century, along with increases in other ‘greenhouse gases’, are a risk to humans. Beyond the gradual changes in climate already noted, larger-scale changes in global circulation systems can follow that may be dramatic in their consequences. In response, the global community has agreed to control the net release of greenhouse gases from both fossil fuel sources and from changes in terrestrial C stocks. Details on how to do this are still being negotiated, but reliable data are needed to move from general commitments to specific actions and to monitor their effectiveness. This Manual of methods aims to contribute to such a process, focusing on changes in terrestrial carbon stocks linked to land use. In the exchange of carbon dioxide (CO 2 ) between terrestrial vegetation and the atmosphere, the net balance between sequestration and release shifts from net accumulation to net carbon (C) release on a minute-by- minute timescale, for example, with cloud interception of sunlight, in a day-night pattern, across a seasonal cycle of dominance of growth and decomposition, and with the stages of the lifecycle of a vegetation or land use system. We focus here on the latter timescale, as part of the annual (or 5-yearly) accounting of land use and land use change. At this timescale, many fluxes can be expected to cancel each other out and we can focus on the net changes in the carbon stock, as the ‘bottom-line’ of many influx (gain) and efflux (loss) processes.

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