Ammonification. When plants and animals die, they get decomposed by decomposers, which include aerobic and anaerobic bacteria and fungi. During decomposition, bacteria convert the nitrogen nutrients back into ammonium and ammonia, which then can go through nitrification and denitrification process again
Decomposers also break down the bodies of dead organisms resulting in nitrogen being returned to the soil as ammonia. In some conditions denitrifying bacteria in the soil break down nitrates and return nitrogen to the air.
Biomes are typically not classified by temperature, because some biomes can experience extreme temperatures from one season to the next. Other biomes might have a more consistent temperature throughout the year.
