Globally, there is more carbon in soils than in the atmosphere and the aboveground biomass together. Plants extract carbon dioxide from the atmosphere by photosynthesis and incorporate it in their cell structures. This carbon then enters the soil as root exudates from living plants, which are utilized by soil organisms, or by decomposition of plant litter. These processes release carbon dioxide back to the atmosphere. They are more or less rapid depending on climate, soil type, land use, and management practices. Since carbon dioxide is a greenhouse gas, increasing soil organic matter stocks in soil is considered as a possible solution to mitigate climate change. Soil organic matter has also beneficial effects on soil fertility, water retention, susceptibility to erosion, and diversity and activity of soil organisms.