Biological importance: Nitrogen is a component of amino acids and nucleic acids.
Forms available to life: Producers can use inorganic ammonium (NH4+) or nitrate (NO3-). Consumers can only use organic nitrogen.
Reservoirs: The main reservoir is the atmosphere, which is 80% nitrogen gas (N2).
Key processes: Nitrogen enters ecosystems through nitrogen fixation by Rhizobium bacteria.
Ammonifying bacteria decompose organic nitrogen to NH4+.
Nitrifying bacteria convert NH4+ to NO3-, while denitrifying bacteria use NO3- in their metabolism and releases N2.