Preparing a soil organic carbon inventory for the United States using soil surveys and site measurements: Why carbon stocks at depth are important

摘要

The Fourth Assessment Report from the Intergovernmental Panel on Climate Change (TPCC) states that current rates of change in greenhouse gases (GHGs) in the atmosphere have increased substantially from those of the past, and are directly related to increases in air temperature. Strong scientific evidence indicates recent and rapid rate increases of GHGs in the atmosphere can be attributed to human influence. Various IPCC (IPCC, 2007) modeling scenarios project an average 2°C or greater global air temperature rise in the next century, if GHGs emissions are not curtailed. Agricultural practices are responsible for three primary greenhouse gas emissions: carbon dioxide (C02), nitrous oxide (N20) and methane (CH4). The agricultural sector has significant opportunities for offsetting GHG emissions: reduction or avoidance of emissions and through carbon sequestration. This project focuses on carbon sequestration efforts. Soil surveys are combined with site measurements to provide the fundamental national inventory needed for assessing the amount of carbon for sequestration. Soil organic carbon is present in significant quantities throughout the soil profile, therefore it is not sufficient to assess only the surface when measuring carbon. Our methods compare surface and near-surface depths distributions of carbon at 5, 20, and 100 centimeters for the United States.