What is a biogeochemical cycle. What is | Class 12 Biology Chapter Ecosystem, Ecosystem NCERT Solutions

The Earth is a closed system with respect to matter and all matter on the Earth cycles. Nutrient cycling (or element cycling) is the movement of elements through both the biotic and abiotic components of the Earth. It is the transport and transformations of elements within and among ecosystems. It involves the incorporation of elements by living organisms and their subsequent release back into the environment through the decomposition. It binds biotic and abiotic parts of ecosystem. The movement of elements through atmosphere, hydrosphere, lithosphere and biosphere is normally termed as Biogeochemical Cycles (bio- living organisms and non- living things and geo means- rocks, air and water etc.). All the organisms require nutrients for their growth and reproduction that includes carbon, hydrogen, oxygen, nitrogen, phosphorus, sodium, Sulphur, chlorine, potassium, calcium and magnesium. The plants obtain these nutrients through the atmosphere by the gaseous cycles or from the soil through the weathering of parent rocks. The function of the reservoir is to meet with the deficit that occurs to imbalance in the rate of influx and efflux. Nutrient cycles or biogeochemical cycles are classified into two types:

1. Gaseous cycle: In this cycle, atmosphere acts as the major reservoir of the element. This cycles shows little or no permanent changes in the distribution and abundance of the element. Carbon and nitrogen are the primary representatives of the biogeochemical cycles with the prominent gaseous phase.
2. Sedimentary cycle: In this cycle, the major reservoir is the Lithosere from which the elements are released largely through the weathering of rocks. This cycle is exemplified by phosphorus, sulphur and other biologically important elements are found; these reservoirs are located in the Earth’s crust. A portion of the supply may get accumulated in the large quantities like in the deep ocean and then become inaccessible to the organisms for the continuation of the cycle.

In the comparison of gaseous cycle to the sedimentary cycle; sedimentary cycle is less perfect because the contents remains locked in the reservoir pool. (Note*: Some of the elements that are characterized by the sedimentary cycle also do have a gaseous phase like Sulphur and iodine but these phases are insignificant cause there is no gaseous large reservoir).    

General model of Nutrient or biogeochemical cycling: