Any study of soil microbial ecology requires that we consider the spatial and temporal interactions of potential reactants such as soil type and moisture content. Hence, the time, location, season of sampling, sample volume, mixing, compositing, and replication are all important for deriving meaningful data (see Chap. 3). Since all samples are by their nature small volumes on which measurements are taken to represent the whole soil, scaling errors can occur frequently. For molecular analyses, it is critical that representative samples are taken, that samples are protected from change between the field and the time they are analyzed in the laboratory, and that samples are not contaminated either by inadvertent mixing with each other or by coming in contact with other samples during handling, transport, and analysis. To avoid altering the composition of the microflora prior to analysis, soil samples should be stabilized as soon as practicable. For molecular measures, soil should be frozen immediately at -20°C and processed within several weeks of sampling. If analyses will be significantly delayed, soil should be stored at -80°C. Unlike sampling for soil chemical and physical parameters, soil drying should be avoided entirely when intended for analyzing microbial populations.
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