Question

biogeochemical 

a. Where do nutrients that ecosystem use come from ? 
b. What happens to the nutrients within ecosystem itself? 
c. What happens to the nutrients once they leave the ecosystem ? 
d. Once the nutrients are cycle, how do they get back ? 
e. What are the rates of exchange of nutrients between the different pools ? 

Answer 1

These nutrients – essentially chemical elements – are continuously in a circular movement, the nutrient cycle. The nutrient cycle is hence a general term that describes how nutrients move from the physical environment into living organisms, and are subsequently recycled back to the physical environment. Nutrients in the soil are taken up by plants, which are consumed by humans or animals, and excreted again by them — or they are released back into the environment when organisms die (e.g. plants lose their leaves). Microorganisms in the soil break this matter down, and again make nutrients available in their mineral form, which makes it possible for plants to take them up again.Essentially, all nutrients that plants and also human beings require to survive are cycled in this way. In relation to water management and sanitation, it is mainly N, P and K that are of high priority. They are the most important nutrients to sustain plant growth and agriculture, and thus humanity.

All the chemicals, nutrients, or elements used in ecosystems by living organisms—such as carbon, nitrogen, oxygen, and phosphorus—operate on a closed system, which means that these chemicals are recycled, instead of lost, as they would be in an open system. The energy of an ecosystem occurs in an open system; the sun constantly gives the planet energy in the form of light, which is eventually used and lost in the form of heat, throughout the trophic levels of a food web.

Although components of the biogeochemical cycle are not completely lost, they can be held for long periods of time in one place. This place is called a reservoir, which, for example, includes such things as coal deposits that are storing carbon for a long period of time. When chemicals are held for only short periods of time, they are being held in exchange pools. Generally, reservoirs are abiotic factors while exchange pools are biotic factors. Examples of exchange pools include plants and animals, which temporarily use carbon in their systems and release it back into a particular reservoir. Carbon is held for a relatively short time in plants and animals when compared to coal deposits. The amount of time that a chemical is held in one place is called its residence time.

The most well-known and important biogeochemical cycles include the carbon cycle, the nitrogen cycle, the oxygen cycle, the phosphorus cycle, and the water cycle.

Biogeochemical cycles always involve equilibrium states: A balance in the cycling of the element between compartments. However, overall balance may involve compartments distributed on a global scale.

Biogeochemical cycles of particular interest in ecology are:

• Nitrogen cycle
• Oxygen cycle
• Carbon cycle
• Phosphorus cycle
• Sulfur cycle
• Water cycle
• Hydrogen cycle