[On methodological aspects of ecological experiments (comments on M. V. Kozlov publication)].
The meaning of conception of pseudoreplication in ecological experiments is discussed. The replications are found to be pseudo if factors causing random variation act on such replications as on one unit. For example, preudoreplications could appear if a single flipped coin would be split up. The absence of random spatial distribution of experimental and control fields could be considered as a mistake because the experimental results could interfere with spatial heterogeneity. However, there are no pseudoreplications in this case, because the variations of ecological systems are produced by factors that are different in different places and each organism responds to these factors individually. The pseudoreplication should be created by multiple determination of a response of an individual organism. Also recommendations for applications of randomized block design and analysis of covariance for field trials in plant communities are proposed. Randomized blocks unite the experimental and control fields occupying the identical place in the series of spatial heterogeneity. The influence of such heterogeneity on random variation of determined parameters could be excluded by this approach. The heterogeneity considered only at the scale of used blocks. As far as control and experimental fields belongs to a single set, the series of heterogeneities, that comprises the range of their parameters, is identical. The random sorting of the large amount of experimental and control samples consisting of the same number of replications will produces replications in the same place of the series of general heterogeneity of investigated set. The replications occupying the same places of the sorted series form "virtual block". The population of such blocks includes the majority of random variation and allows one to reveal even very weak experimental effects by variance analysis.
Tatarnikov
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D000704:Analysis of Variance; D000818:Animals; D004463:Ecology / Q000379:methods*; D010944:Plants; D012107:Research Design