Decomposer

Heterotrophic organisms, chiefly the microorganisms, that break down the bodies of dead animals or parts of dead plants and absorb some of the decomposition products while releasing similar compounds usable by producers.

Source
Society for Range Management. 1998. Glossary of terms used in range management, fourth edition. Edited by the Glossary Update Task Group, Thomas E. Bedell, Chairman. Used with permission.