biomass

biomass, the weight or total quantity of living organisms of one animal or plant species (species biomass) or of all the species in a community (community biomass), commonly referred to a unit area or volume of habitat. The weight or quantity of organisms in an area at a given moment is the standing crop. In a separate but related usage, the term biomass refers to plant materials and animal waste used especially as a source of fuel.

In contrast, the total amount of organic material produced by living organisms in a particular area within a set period of time is called primary productivity (that is, biomass production by plants and other photosynthetic organisms) and secondary productivity (that is, biomass production by animals). Primary and secondary productivity are usually measured as rates in units of energy per unit area per time, such as gram calories or kilojoules per square meter per year. Measures of weight, characterized as the mass of carbon per unit area per time—such as tons of carbon per square kilometer per year or gigatons of carbon per year—are also commonly recorded.