Biogenic carbon: Carbon that is recently derived from organic sources such as plants, animals, and microbes. This does not include fossil carbon.

Carbon cycle: The flow of carbon through the atmosphere, vegetation, soil, and lithosphere (land and rocks).

Carbon emissions: Carbon that moves from the forest (or other ecosystem) into the atmosphere, contributing to the greenhouse gas effect. Carbon emissions are usually referred to as a flux and are expressed as a rate. Carbon emissions are part of a natural carbon cycle; humans have disrupted the carbon cycle primarily by moving fossil fuels into the active carbon cycle.

Carbon flux: The movement of carbon between pools or between the atmosphere and land.

Carbon pool: A reservoir that stores carbon. Ecosystem carbon pools can be defined in several ways, but generally include the following: aboveground live biomass (trees, shrubs, herbs, grasses), belowground live biomass (roots), dead wood (standing dead trees, stumps, downed dead wood), forest floor (litter, leaves, partially decomposed organic matter such as small branches), and soil.

Carbon sink: A pool or reservoir that stores more carbon than it releases.

Carbon storage (stock): Amount of carbon retained in a carbon pool. This is a stock, commonly expressed as units of carbon stored in a forest pool per area.

Carbon uptake (sequestration): Process by which plants take up atmospheric carbon dioxide and convert it to biomass. This is a flux and is expressed as a rate, commonly in units of carbon sequestered from the atmosphere into forests per area per year.

Fossil carbon: Carbon that is originally derived from organic sources and has been buried underground for millions of years. Extreme temperature and pressure transforms this carbon into coal, oil, or natural gas. Extraction of this fossil carbon by humans starting in the mid 19th century for fossil fuels use has led to disruption of the natural carbon cycle and rapid accumulation of carbon dioxide in the atmosphere. 

Global carbon budget: Summation of all the emissions of carbon to the atmosphere and all the carbon removed from the atmosphere by the land and ocean.

Mean residence time: The average time something (e.g., a carbon molecule) is stored in a given pool before moving out of that pool.

Other Terminology

Biodiversity: The variety of living things that make up a system.

Biomass: The total mass of organisms in a given ecosystem at a given time. For example, live tree biomass in a forest stand is composed of all  living tissue of the trees of a stand including foliage, branches, stem, and roots..

Blowdowns: Disturbance events that  topple trees, usually due to strong winds

Deforestation: The conversion of forest to non-forest use.

Disturbance: A human or natural discrete event, such as one caused by fire, disease, or drought, that alters an ecosystem’s structure, composition, or function

Forest management: Planned human intervention within a forest ecosystem using different practices, tools, and techniques to meet certain management goals.

Forest stand: A section of forest that has relatively uniform species composition and structure. The forest stand serves as the basic unit of forest management.

Greenhouse gas effect: A natural process where certain gases (greenhouse gases) in the Earth’s atmosphere trap heat near the Earth’s surface.

Harvested wood products: Wood-based materials harvested from forests that are used to create products such as furniture, paper, plywood, etc.

Land use change: The human conversion of one landscape type into another type, usually for economic use.

Mesophication: The process by which a forest composed of fire-dependent species shifts in composition to include more tree species that prefer wetter conditions and are less drought tolerant. Changes in microclimatic conditions create a reinforcing feedback loop that limits fire and continues to favor moisture-loving plant species. 

Net primary productivity: The net increase (i.e., photosynthesis minus respiration) in total plant carbon, including above- and below-ground plant carbon.

Photosynthesis: The process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar.