xxxvi. Biogeochemical cycles

UPSC Sample Notes [English]

Biogeochemical cycle:

Any of the natural pathways by which essential elements of living matter are circulated can be called the biogeochemical cycle.
The term biogeochemical is a contraction that refers to the consideration of the biological, geological, and chemical aspects of each cycle.
Elements within biogeochemical cycles flow in various forms from the nonliving (abiotic) components of the biosphere to the living (biotic) components and back.
Each biogeochemical cycle can be considered as having a reservoir pool, a larger (slow-moving, usually abiotic portion), and an exchange (cycling) pool (a smaller but more active portion) concerned with the rapid exchange between the biotic and abiotic aspects of an ecosystem.
Energy and nutrient circulation are the major functions of the ecosystem. Energy is lost as heat whereas nutrients are recycled indefinitely.

Types of biogeochemical cycling:

A nutrient cycle is gaseous or sedimentary based on the nature of the reservoir.

Gaseous cycle:

The main reservoir of nutrients is the atmosphere and the hydrosphere.
Gaseous cycles tend to move more rapidly to adjust more readily to changes in the biosphere because of the large atmospheric reservoir.
Extraordinary disturbances (such as global warming) and more-frequent local disturbances(such as wildfires and storm-driven events) can, however, seriously affect the capacity for self-adjustment.
Examples: water cycle, oxygen cycle, carbon cycle, nitrogen cycle, etc.
They are usually perfect- nutrients are replaced as fast as they are utilized.

Sedimentary cycle:

The main reservoir is the soil and the sedimentary and other rocks of the earth’s crust.
Sedimentary cycles vary from one element to another, but each cycle consists fundamentally of a solution(or water-related) phase and a rock (or sediment) phase.
Examples: phosphorus cycle, sulfur cycle, calcium cycle, magnesium cycle, etc.
These are imperfect as some nutrients lost get locked into sediments and are unavailable for immediate cycling.

Importance of biogeochemical cycle:

The proper functioning of the various biogeochemical cycles is crucial for life forms on the earth. These cycles transform matter from one form to another for use of different organisms and natural systems. These cycles facilitate the storage of various elements for long-term and short-term usage.
These cycles connect different ecosystems and sustain them as well by maintaining a continuous flow of matter and energy through them. all the variants of the ecosystems whether living or non-living are interconnected through these cycles.