Original article Consequences of reducing a full model of variance analysis in tree breeding experiments

Summary — An analysis of variance was performed on height measurement of 11-year-old trees (7 in the field), using the results of a non-orthogonal progeny within provenance experiment establi-shed for Norway spruce (Picea abies (L.) Karst.) at 2 locations in Poland. The full model including locations, provenances, progenies within provenances, blocks within locations and trees within plots is used assuming all sources of variation to be random. This model is compared with various models reduced by 1 factor or the other within the model. Theoretical modifications of estimated variance components and heritabilities are tested with experimental data. By referring to the original model it is shown how changes came to be and where the losses of information occurred. A method is pro-posed to reduce the factor level number without bias. The general conclusion is that it pays to make the effort and work with the full model