NUTRIENT CYCLE

The cyclic conversions of nutrients from one form to another within the biological communities. A simple example of such a cycle would be the production and release of molecular oxygen (O2) from water (H2O) during photosynthesis by plants and the subsequent reduction of atmospheric oxygen to water by the respiratory metabolism of other biota. The cycle of nitrogen is much more complex, with the nitrogen atom undergoing several changes in oxidation state (N2, NO3-, R: NH2, and NH4+, among others) during the cycling of this element through the biological community, and into the air, water, or soil, and back.