Nutrient Cycles

Nutrient cycles describe the cycling in terrestrial, limnic, or marine ecosystems and in compartments of these ecosystems of those elements and chemical compounds that are essential for maintaining life. The essential elements include the macronutrients (nitrogen [N], potassium [K], calcium [Ca], magnesium [Mg], phosphorus [P], and sulfur [S]—ordered in the sequence of the mass contributions of these elements to dry shoot matter of higher plants according to Marschner, 1995) and the micronutrients (chlorine [Cl], boron [B], iron [Fe], manganese [Mn], zinc [Zn], copper [Cu], nickel [Ni], and molybdenum [Mo]). Some microorganisms, animals, and humans additionally require other elements such as chromium (Cr), selenium (Se), and [Page 2053]vanadium (V). Carbon and water, which are also needed by all living organisms, are usually not considered as nutrients. ...