Organic matter cycling

Williams, P.M., 1971. The distribution and cycling organic matter in the ocean. In S.J. Faust and J.V. Hunter (Editors), Organic Compounds in Aquatic Environments. Marcel Dekker, New York, N.Y., pp. 145—163. 

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. 

Fresh organic matter plays a fundamental role in plant nutrition by supplying nutrients released through degradation processes however, humified organic substances also become a source of nutrients when subjected to mineralization processes. The main aspects of the cycle of organic matter at the rhizosphere soil are reported in Chap. 6. 

Carbon Dioxide. Carbon dioxide, also a colorless and odorless gas, makes up about 0.03% of dry air. Carbon dioxide is introduced into the atmosphere by several natural processes it is released from volcanoes, from burning organic matter, and from living animals as a byproduct of the respiration process. It is for this latter reason that carbon dioxide plays a vital role in the carbon cycle (see Fig. 62), which makes possible one of the more important scientific tools in archaeology, radiocarbon dating (see Textbox 52). 

Denier van der Gon HAC, Neue HU. Influence of organic matter incorporation on the methane emission from a wetland rice field. Global Biogeochem. Cycl. 1995 9 11— 22. 

---