Towards an Integrated Methodology for Measuring and Monitoring Soil Carbon at Regional Scales (Invited)

Soil carbon accounts for the second largest stock of the biosphere. Agricultural soils contain an important fraction of the total stock and depending on management and environmental conditions can behave as sources or sinks of atmospheric carbon dioxide. Implementation of improved agricultural practices and restoration of land productivity can lead to soil carbon sequestration and therefore contribute not only to mitigate climate change but also satisfy the food, fiber, and bioenergy demands of future generations. Further, increasing soil carbon and, thus, soil organic matter, would improve the adaptive capacity of agricultural soils to withstand or attenuate the negative effects of climate change. At the site scale, soil carbon—at times with great precision—has been measured, monitored, and modeled often using long-term observations. At the regional level, however, soil carbon changes are usually modeled using accounting methods, biogeochemical simulations, and remotely sensed data. These procedures usually generate uncertainty in the estimation of soil carbon change due to the lack of local observations, spatial or temporal scales that these studies are conducted, and lack of information concerning the kinetic status of the soil carbon pools. Recent advances in techniques to measure and map soil carbon, conduct spatial simulations of soil carbon, and remotely sense biophysical variables such as yield, net primary productivity, residue cover, and soil moisture promise to enhance our capability to develop an integrated methodology to measure and monitor soil carbon changes at regional scales. Implementation and testing of this type of integrated technologies will be crucial for building robust soil carbon accounting systems be these of regional or national nature.