Næringsstoffkretser

Næringsstoffkretser, also known as nutrient cycles or biogeochemical cycles, describe the pathways by which nutrients move through the Earth's biotic and abiotic components. These cycles are fundamental to the functioning of ecosystems, as they ensure the continuous availability of essential elements for life. Key nutrients involved include carbon, nitrogen, phosphorus, and water.

The carbon cycle, for instance, involves the exchange of carbon between the atmosphere, oceans, land, and living organisms. Photosynthesis by plants removes carbon dioxide from the atmosphere, while respiration and decomposition release it back. The nitrogen cycle is crucial for the production of amino acids and nucleic acids. It involves processes like nitrogen fixation, nitrification, and denitrification, which transform nitrogen between different chemical forms.

Phosphorus, primarily found in rocks and soil, moves through terrestrial and aquatic ecosystems. Its cycle is slower than carbon and nitrogen, and it lacks a significant atmospheric component. The water cycle, or hydrologic cycle, involves the continuous movement of water on, above, and below the surface of the Earth, driven by solar energy and gravity, involving evaporation, transpiration, condensation, precipitation, and runoff.

Disruptions to these nutrient cycles, often caused by human activities such as pollution, deforestation, and the use of fertilizers, can have significant ecological consequences, including eutrophication of water bodies and climate change. Understanding and protecting nutrient cycles is therefore vital for maintaining ecosystem health and sustainability.