Nutrient Cycling

· The amount of nutrients present in the soil at a given time is known as the standing state.

· Nutrients are never lost from the ecosystem. They are only recycled from one state to another.

· The movement of nutrients through the various components of the ecosystem is called nutrient cycling or biogeochemical cycles. They are of two types:

o Gaseous

o Sedimentary

Gaseous

Reservoir for these types of cycles exist in the atmosphere.

Sedimentary

Reservoir for these types of cycles exist in the earth’s crust.

Carbon Cycle

Ø About 49% of the dry weight of living organisms is made up of carbon.

Ø The ocean reserves and fossil fuels regulate the amount of CO₂ in the atmosphere.

Ø Plants absorb CO₂ from the atmosphere for photosynthesis, of which a certain amount is released back through respiratory activities.

Ø A major amount of CO₂ is contributed by the decomposers who contribute to the CO₂ pool by processing dead and decaying matter.

Ø The amount of CO₂ in the atmosphere has been increased considerably by human activities such as burning of fossil fuels, deforestation.

Phosphorus Cycle

Ø Phosphorus is an important constituent of cell membranes, nucleic acids, and cellular energy transfer systems.

Ø Rocks contain phosphorus in the form of phosphate.

Ø When rocks are weathered, some of the phosphate gets dissolved in the soil solution and is absorbed by plants.

Ø The consumers get their phosphorus from the plants.

Ø Phosphorus returns back to the soil by the action of phosphate-solubilising bacteria on dead organisms.