The Nitrogen Cycle
The Nitrogen Cycle
The nitrogen cycle is a complex biological cycle involving the recycling of usable nitrogen. If this cycle ceased to occur, all forms of life on the planet would die. All life forms, including humans, use nitrogen in compounds called amino acids. These amino acids then act as building blocks for proteins. Nitrogen, in fact, is the most abundant element in the atmosphere. Most organisms are unable to use this nitrogen from the atmosphere and rely on the nitrogen in the soil.
The cycle consists of three distinct parts: ammonification, nitrification, and assimilation. The first part of the cycle is ammonification. This process consists of the recycling of nitrogen from waste back into a nitrogen compound called ammonia (or ammonium). The nitrogen that enters the soil comes from trees when they rot on the ground after dying, and from wastes excreted by animals. Bacteria in the soil use these nitrogen compounds to form their own proteins and release the nitrogen as ammonia.
The next step in the cycle is that of nitrification. This involves a change in the oxidation state of nitrogen. In very basic terms, this involves the nitrogen in ammonia (NH3) transforming into nitrate (NO3-). Once the nitrogen is in the nitrate form, it can be assimilated back into the roots of the tree from the soil. This is the third and final step of the cycle. Once in the tree, the nitrogen can be transferred to animals by eating from the tree, or eating other animals that have eaten from the tree. When this tree grows old and dies, or when the animals release waste, the cycle can start all over again.
As you can clearly see, the nitrogen cycle is essential to existence of all life on earth. As well as playing a key role in the nitrogen cycle, some trees and bacteria also take place in something called nitrogen fixation. This refers to nitrogen from the atmosphere being brought down to the earth and incorporated into the nitrogen cycle. The rainforest is an extremely important resource because it plays an important role in the nitrogen cycle and contains many trees that are good nitrogen fixers—providing us with more of the nitrogen that is vital for life.