Other reports in this collection 1.3.1. Within each biome, large additional variation exists resulting from local conditions and topography. These carbon quantities will eventually be returned to the atmosphere when patches of trees die for biological or climatic reasons, localized natural disturbance occurs, or compartments of the forest are cleared. In most grassland types, below-ground NPP is at least equal to or higher than aboveground production.
Wetlands are important reservoirs of carbon.
Peatlands drained for agriculture continue to be a sustained carbon source as long as any peat remains in the soil. Losses of carbon from terrestrial systems during the past 200 years, particularly until the middle of the 20th century, were mostly the result of the establishment of agriculture on grassland and land that was previously covered by forests. Regular plowing, planting, and harvesting led to enhanced oxidation of organic matter in the soils, which has been emitted into the atmosphere as carbon dioxide. Soil organic carbon in cultivated soils is continuing to decline in many areas of the world.