The Nitrogen Cycle

Nitrogen Cycle

Worksheet to lead students to an independent research and understanding of the role of nitrogen in an ecosystem.


Ammonification This is the process in which organic forms of nitrogen (e.g., nitrogen present in dead plant material compounds) are converted to ammonium (NH4+) by decomposers (bacteria).
Nitrate (NO3-) A form of nitrogen that is available to plants as a nutrient. In high concentrations, it is a water pollutant.
Nitrification Nitrification is the process in which ammonium is converted to nitrite and then nitrate. This process naturally occurs in the environment, where it is carried out by specialized bacteria.
Nitrogen Fixation The process by which nitrogen gas (N2), a form of nitrogen that is readily available in the atmosphere but that cannot be used by plants, is converted to ammonium (NH4+), a form of nitrogen that can be used by plants. Nitrogen fixation is accomplished naturally by bacteria and by lightning, and by humans in industrial processes such as the production of fertilizer.
Nitrogen Mineralization This is the process in which organic forms of nitrogen (e.g., proteins in dead plant material) are converted by microbes to inorganic forms of nitrogen (e.g. ammonium and nitrate).
Nitrogen Saturation Nitrogen saturation occurs when nitrogen inputs saturate the retention capacity of a forest ecosystem. That is, as more and more nitrogen is deposited on forests (due to increases in nitrogen emissions and corresponding increases in deposition), eventually forests will no longer be able to absorb all the nitrogen. This could lead to increased nitrate leaching (which could pollute streams, lakes and drinking water), soil acidification, and maybe even forest health problems.