Carbon cycle is a fundamental biogeochemical concept and area of Earth system science research that investigates the dynamic exchange, transformation, and storage of carbon atoms among the Earth's major reservoirs: the atmosphere, oceans, terrestrial biosphere, and lithosphere. It examines the physical, chemical, and biological processes driving carbon flux between these compartments, such as photosynthesis, respiration, decomposition, combustion, and geological processes, and is critical for understanding Earth's climate system, ecosystem functioning, and the impact of anthropogenic activities.