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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.