Biogeochemical cycles describe how organisms can continuously survive over millions of years. The recycling of water, carbon, and nitrogen are the most important cycles in the biosphere. Water, carbon, and nitrogen undergo changes to form different physical and chemical state in a continuous process. They pass through food webs and are combined and recombined in different ways. Each of their steps within the cycles affects both biotic and abiotic components.
Biogeochemical Cycles: The passing and recycling of different chemical elements through biotic and abiotic components of the biosphere.
Exchange Pool: Part of a biogeochemical cycle that holds water or another element for a short period of time.
Reservoir: Part of a biogeochemical cycle that holds water or another element for a long period of time.
Water Cycle: The continuous movement of water in our biosphere.
Evaporation: The process where water in its liquid form changes into its gas form.
Sublimation: Water in its solid state directly forms water vapor.
Transpiration: Occurs when plants release water through leaf pores called stomata.
Condensation: The process in which water vapor changes into tiny droplets of water.
Precipitation: A stage that may occur after condensation. If the tiny droplets get large enough, they will fall.
Groundwater: Precipitation that is absorbed into the ground.
Carbon Cycle: The continuous process in which carbon is exchanged throughout the biosphere.
Nitrogen Cycle: Process by which nitrogen moves through the biosphere.
Assimilation: When plants absorb and incorporate nitrogen into organic compounds.
Nitrogen Fixation: The process of combining nitrogen with hydrogen to form ammonia.
Nitrification: Production of nitrate from ammonia.
One important biogeochemical cycle is the water cycle. There is no beginning or end to the water cycle. The cycle takes place on, above, and below Earth’s surface. We often think of water in its liquid form, but it can also exist as a gas (water vapor) or a solid (ice). The form of water changes as it goes through the water cycle.
Liquid → Gas:
Gas → Liquid:
Not all parts of the water cycle proceed at the same speed. A reservoir like the ocean is capable of holding liquid water for a long time.The atmosphere, however, is an exchange pool that can only hold water for a couple of days.
The carbon cycle is another important biogeochemical cycle.
Although not as obvious as the water cycle and the carbon cycle, the nitrogen cycle is also an important biogeochemical cycle.