quantitative term used in ecology to describe the amount of biological material (total weight) of a certain species or group of species in a certain area. Biomass can be expressed as so-called "wet-weight" (bruto weight of the living or dead organism), dry-weight (after drying in an oven to exterminate the water) and ashfree dry-weight (after incineration in an oven to exterminate all carbohydrates). Nowadays carbon weight (difference between dry-weight and ashfree dry-weight) is considered to be the most usable unit in ecological studies.