Woody organic matter

Dead vegetation also afreets the global carbon cycle. Dead organic matter decomposes, releasing carbon dioxide to the atmosphere. Rates of decomposition vary with material, location, and climate. Non-woody organic matter decomposes rapidly woody organic matter slowly. Decomposition tends to occur faster at the soil surface than below. Decomposition is relatively fast in warm moist climates. In cold climates and in wetlands, decomposition is so slow that there is a net increase of stored carbon in the soil and organic soils called, "histosols, are formed. 

Grasses and other similar plants, which may be annual, biennial, or perennial in their growth habit, do not have woody components, but also add leaves and stems to the soil each year. These leaves and stems decompose over a 1-year period, adding organic matter to the soil surface. Often these leaves seem to decompose faster than tree leaves however, in all cases, the rate of decomposition will largely depend on both the characteristics of the plant material and local environmental conditions. 

The second source of biochemicals is molecules excreted from cells such as extracellular enzymes and other organic matter. A typical example is cellulase, which is excreted by fungi such as Penicillium in order to break down wood and woody material into sugars that can be used by the organisms. Other common extracellular enzymes found in soil are ureases and amylases. Often enzymes are associated with clay particles, and in such associations, their activity may be increased, decreased, unchanged, or completely destroyed [15],... 

The USDA (1999) defines organic wetland soils as having an organic carbon content of at least 12 % if the mineral fraction has no clay, 18 % if > 60 % clay, or 12-18 % if < 60 % clay. Further differentiation is based on the botanical origin of the organic matter-whether mosses, herbaceous plants, or woody plants-and its state of decomposition fibrists contain predominantly recognizable, little-decomposed plant debris, saprists predominantly well-decomposed plant debris. 

Saprophyte—This refers to an organism that derives its energy by decomposing dead organic matter. Many species of mushroom-producing fungi live off the organic debris that is present in the mineral soil and, especially, the surface litter of leaves and woody debris on the forest floor. 

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