Biomass

Definition

The total mass of living organisms in a given area, volume, or trophic level, expressed as dry weight or wet weight. In arthropod studies, biomass serves as a currency for comparing production, consumption, and energy flow across taxa of vastly different sizes, and is often partitioned into standing crop biomass (present at one time) versus productivity (biomass accumulated over time).

Etymology

From Greek bios (life) + maza (mass, barley cake), via modern ecological usage.

Example

A single colony of army ants (Eciton burchellii) may contain 10^6 workers with a collective wet biomass exceeding 20 kg, yet consumes roughly 30,000 prey items daily—demonstrating how high biomass turnover, not merely standing biomass, drives ecosystem predation pressure in tropical forests.

Synonyms

• phytomass
• zoomass

Related Terms

• standing crop
• productivity
• Trophic level
• allometry
• dry weight
• fresh weight
• energy flow
• production-to-biomass ratio

Usage Notes

Dry weight is preferred for arthropod biomass measurements to remove variable water content; fresh weight is sometimes reported for live collections. In entomology, biomass is frequently used to scale physiological rates (metabolism, consumption) and to compare guilds—e.g., herbivorous beetle biomass versus predatory spider biomass in the same habitat. The term excludes dead organic matter (detritus, necromass). Contrast with abundance (individual count), which can diverge sharply from biomass when size varies: a habitat may host millions of springtails yet less biomass than a few hundred scarab beetles.