ABSTRACT
Both human and natural disturbances affect carbon storage and flux in forested ecosystems, including harvesting, conversion to agriculture or pasture, wildfire and fire suppression, and pest and disease outbreaks. Forests are sources of atmospheric carbon dioxide (CO2) when total respiration or oxidation of plants, soil, and dead organic matter exceed net primary productivity. Conversely, forests can become carbon sinks when agricultural land and pasture are abandoned and revert naturally to forests, or are restored to native forests or plantations through afforestation. Aggrading forest ecosystems also fix more carbon than they respire. Forests play an important role in the global carbon cycle because they store large quantities of carbon in vegetation and soil, exchange carbon with the atmosphere through photosynthesis and respiration, are sources of atmospheric carbon when they are disturbed, and become atmospheric carbon sinks (i.e., net transfer of CO2 from the atmosphere to the land) during regrowth after disturbance (Brown et al. 1996a). Humans have the potential to alter the magnitude of forest carbon stocks and the direction of forest carbon fluxes through changes in landuse and management, and thus alter the role of forests in the global carbon cycle.
