The nutrients are never lost from an ecosystem but are recycled time to time and again indenfinitely.Nutrient cycles are of two types :
1. Gaseous cycles : The reservoir for gaseous cycles exists in the atmosphere, e.g., carbon cycle, nitrogen cycle.
Sedimentary cycles : The reservoir for sedimentary cycles exists in the earth's crust, e.g., phosphorus cycle, sulphur cycle.
The function of the reservoir is to meet with the deficit, which occurs due to imbalance in the rate of influx and efflux.