The primary building blocks of all plant tissue is essentially carbon, hydrogen and oxygen, however there are 14 other elements that are required to maintain existing tissue and build new biomass. These elements are termed nutrients.

Plants collect nutrients from the soil and combine them with carbon to build biomass and later return the nutrients to the soil in the form of dead leaves, needles, branches and stems (Mackenzie et al. 1998). The material then undergoes decomposition in the forest floor to complete the nutrient cycle. The nutrient cycle is termed a biogeochemical process since it is controlled by the activity of plants, soil microorganisms, and geochemical process of the soil.