In most ecosystems nitrogen is primarily stored in living and dead organic matter. This organic nitrogen is converted into inorganic forms when it re-enters the biogeochemical cycle via decomposition. Decomposers, found in the upper soil layer, chemically modify the nitrogen found inorganic matter from ammonia (NH3 ) to ammonium salts (NH4+ ). This process is known as mineralization and it is carried out by a variety of bacteria, actinomycetes, and fungi.