Decomposition Methods

The use of litter bags is one of most common field techniques for litter decomposition studies to the point that it has become a sort of standard method in studies on decomposition. This method is used both for the quantitative assessment of litter biomass loss and for studies on its chemical changes. In this method, a bag is filled generally with 1-10 g of litter dried at room temperature until a constant moisture level is reached. High temperatures are avoided in the preparation of these litter samples to prevent important changes in microbial community and fiber structure. The bag is first exposed to field conditions for a specific time period, and then it is brought back to the laboratory for reweighing and performing chemical analyses on the remaining litter using techniques such as atomic emission spectrometry (AES), atomic absorption spectrometry (AAS), and inductively coupled plasma spectrometry (ICP). A typical litter bag size is between 10 x 10 cm and 20 x 20 cm and it is made of biologically resistant polyester or nylon. Nylon is not used in N studies because this material contains N. Mesh size and incubation time depends on aim of the study and the precision required. Sometimes a certain mesh size is purposely employed to exclude particular groups of soil fauna in order to determine their functional significance to decomposition processes. The number of replicate bags is important for the accuracy in mass loss estimation and the minimum of bags must be sufficient to estimate the decomposition rate constant k adequately. The study methods for woody detritus decomposition are analogous to the litter bags method, though they usually do not use litter confinement. Other methods commonly used to investigate decomposition include microcosm studies, or laboratory and field techniques based on the measurement of concentration and fluxes of soil CO2 through time. These measurements allow separating the different contributions to soil organic matter loss (e.g., carbon mineralization vs. leaching).

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