Which concept describes the circulation of elements through all spheres and the flux between pools?

• A. Hydrologic Cycle
• B. Nutrient Cycles
• C. Net Primary Productivity
• D. Gross Primary Production

Answer: (B)

Nutrient cycles describe how elements move through every part of the Earth system—air, water, soil, and living organisms—and how they flow between different pools or reservoirs. Elements like carbon, nitrogen, phosphorus, and sulfur are transformed and transferred through processes such as fixation, mineralization, uptake by organisms, decomposition, and sedimentation, allowing them to be stored in soils or sediments and later released and reused. This circulating, interconnected movement of nutrients across all spheres is what the term captures. The hydrologic cycle, by contrast, is mainly about water movement, while concepts like net and gross primary production focus on how much energy from photosynthesis is captured and stored as biomass, not on the broad circulation of elements among pools.