Organic matter

Soil organic matter consists of fresh litter, partially decomposed organic materials, and humus. As fresh litter is decomposed to humus, the plant nutrients contained within the organic matter are slowly released making them available for biological uptake. Soil organic matter is a very important nutrient pool in forest ecosystems, especially for nitrogen, sulfur, and phosphorus (see Table 10 and Table 12.) The pool of nutrients contained in organic matter is made slowly available through decomposition and mineralization by microorganisms over a period of months to years. The mean residence time of soil organic matter ranges widely (0.4 to 353 years) depending on the litter quality and the environmental conditions. Nutrient release from organic matter has a similar but not identical mean residence time compared to the organic matter itself. See DECOMPOSITION and MINERALIZATION for more information on organic matter transformations in the soil environment.