Figure 11.

Conceptual model of the carbon cycle emphasizing the role of reactive dissolved organic matter (RDOM) as a choke point or regulator. (a) While biomass and particulate organic matter contain most of the Earth's organic carbon, the pool of reactive DOM as determined by environmental and inherent factors regulates biogeochemical processes such as respiration, nutrient mineralization, methanogenesis, and denitrification. (b) The amount of reactive DOM at a given moment in space and time depends on two‐way interactions among environmental conditions and DOM properties. Together, these dynamics regulate the persistence and processing (biotic and abiotic) of DOM. The curved arrows provide examples of links between DOM properties and environmental conditions. The inherent factors that influence DOM degradability are both cause and consequence of the environmental factors that interact to determine realized reactivity (actual rates of DOM alteration, assimilation, or mineralization).