DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/1966 str. 90 <-- 90 --> PDF |
ADAPTING PROVENANCE TRIALS TOWARDS THE MOST EFFICIENT SELECTION AND PRESERVATION OF DESIRABLE FOREST POPULATIONS (Contributed paper) by MACIEJ M. GIERTYCH Institute of Dendrology and Körnik Arboretum, Polish Academy of Science, Poland. Earlier provenance tests that have yielded so useful information, have been laid out on fairly large plots, however, they were usually without or with only few replications. In recent years it has become obvious that in order to obtain a truly reliable comparison of provenances, replication in essential and the number of replicates needed is considerably larger than was anticipated earlier. When introducing several replicates the experimenters had to reduce the plot size in order to keep the experiment within manageable limits. A discussion ensued as to the most efficient ratio between plot size and number of replicates. Wright and Freeland (1958) have calculated that most information per tree is obtained when dealing with plots containing only one tree each. The main purpose of provenance trials is to compare the provenances and to select the best. Evaluation of the productivity of a provenance may not be possible from single trees. There are of course also other objections to the use of single tree plots. Earlier provenance tests have shown that it is not always possible to locate the same stand from which the seed was collected for an experiment. In fact the collection is either made on fellings, or the stand is felled in the period between the seed collection and the time when the provenance tests have yielded reliable results. Thus the information obtained is at best an indication of the expected value of the principal region in which the provenance was located. The exact original population may not be available for the utilization of the experimental results in practice. In this case the population can only be reconstructed from the trees still remaining on the experimental site. These trees will constitute an even better population than the original one, since by means of thinnings it was further selected for the specific conditions of the new locality on which its progeny is growing. Thus the general requirements that have to be specified for the provenance trials now established are that the trials must provide reliable information about the differences between the provenances in respect of their economically important characters, and also that they must provide enough trees per provenance at the end of the experiment, to permit a reconstruction of the original population. |