Biological Phosphorus Cycling in Arctic and Alpine Soils

Abstract

Soil phosphatases, particularly acid and alkaline phosphomonoesterases, have been extensively studied [see reviews by Ramirez-Martinez (Folia Microbiol 13:161--174, 1968); Speir and Ross (Soil phosphatase and sulphatase. Soil enzymes. Academic, London, pp 197--250, 1978); Malcom (Soil Biol Biochem 15:403--408, 1983); and Tabatabai (Soil enzymes. Methods of soil analysis. Part 2. Microbiological and biochemical properties. Soil Science Society of America, Madison, pp 775--833, 1994)] because they mineralise organic phosphorus (P) to inorganic P. The effects of agricultural and forest managements, pollutants and any environmental factor on phosphatase activities of soil cannot be adequately interpreted because the currently available enzyme assays do not discriminate between the contribution of phosphatases associated with active microbial cells and that of extracellular phosphatases stabilised by soil colloids. Despite multiple evidence indicating that phosphatases can be adsorbed by surface-reactive particles such as clay minerals or entrapped by humic materials, the visualisation of the extracellular phosphatases in the soil matrix has never been achieved because ultracytochemical tests combined with electron microscopy cannot locate enzymes in electron-dense minerals such as clays, or in soil components such as humic materials, that react with counterstainers such as OsO 4 .