The pool of organic matter accumulated in the surface terrestrial soil is larger than the amount of carbon (CO2) in the atmosphere (Fig. 6.1). Only the pool of oceanic carbon is larger than that in the terrestrial soil organic horizons. The source of organic matter in the soil is estimated globally from biogeochemical cycles and data obtained from various ecosystems (Schlesinger, 1997). It is estimated that 560 X 1015 g C is held in terrestrial plant tissues, mostly as wood. A fraction is shed annually as litter from roots, leaves and woody debris for decomposition. The soil organic matter (SOM) consists of annual additions of plant-derived litter, as well as litter from organisms of the above-ground production food webs (Fig. 6.2). It also includes litter from saprotrophic organisms, as dead organisms, shed body parts and excreted wastes. The SOM is decomposed by saprotrophs releasing CO2 and metabolic wastes, as well contributing to new biomass through growth of cells, cell divisions and sexual reproduction, yielding new individuals (Fig. 6.3). In terrestrial systems, decomposition of SOM into CO2 is the largest source of carbon anthropogenic sources and fossil fuels 6 x 1015 g C/year
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Your Alternative Fuel Solution for Saving Money, Reducing Oil Dependency, and Helping the Planet. Ethanol is an alternative to gasoline. The use of ethanol has been demonstrated to reduce greenhouse emissions slightly as compared to gasoline. Through this ebook, you are going to learn what you will need to know why choosing an alternative fuel may benefit you and your future.