Decomposition Lab 5

Topics: Soil, Humus, Organic matter Pages: 4 (1061 words) Published: January 8, 2012
Lab 5


Decomposition is the breakdown of organic material into its smaller molecules and elements. (This term is generally considered as a biotic process but one may find it also used to describe an abiotic process, e.g., due to weathering.) The decomposing organisms may use the release of elements for nutrients and by breaking apart the carbon-carbon bonds in organic matter this can release energy for them. These smaller molecules and nutrient elements may also become available for use by the primary producers (i.e., plants and phototropic microorganisms). Decomposition is an important step in the food chain and contributes to the nutrient cycling within an ecosystem. Most of the organic matter in an ecosystem ultimately passes through the decomposer subsystem.

Decomposition of organic matter is a major ecosystem process involving an array of different organisms. The catabolism (breakdown of molecules into smaller units) of the organic compounds is mostly accomplished by bacteria and fungi. However if one considers decomposition as the disappearance or breakdown of organic litter then the soil fauna (invertebrates such as the springtails, mites, isopods, etc) must be included in this array of soil biota that contributes to the decomposition of organic matter. Wood decomposition is also influenced by the fungal species that break it down. Some of these species form brown rot (where only cellulose and hemicellulose are broken down leaving lignin which is brown), while others form white rot where all three are broken down). The majority of fungi are white rotters, but brown rot fungi are ecologically important because they form long-lived nurse logs.

Decomposition rates vary due to abiotic factors such as moisture level, temperature, and soil type. The rates also vary depending on the amount of initial breakdown caused by the prior consumers in the food chain. The more broken down the organic matter...
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