Non-random Height Pattern Formation in Even aged Scots Pine (<i>Pinus syhestris</i> L.) Nelder Plots as affected by Spacing and Site Quality

A competition experiment with even age Scots pine ( Pinus sylvestris L.) in Nelder design was established on a poor arid a rich site. The experiment was of 4 years' duration. Size of neighbouring trees were compared by means of a function of differences in their heights. A computer intensive statistical test was developed to examine the existence of clusters of trees of uniform height. The test estimated the probability of the measured variability in height resulting from random processes within applied spacings. Site fertility affected the appearance of significantly non-random height patterns, i.e. tree groups of several large and small individuals. The patterns first appeared on the rich site at spacings from 0.157 to 0.396 m 2 /tree and widened on spacings from 0.046 to 1.365 m 2 /tree during the experiment. The appearance of the pattern was delayed on the poor site until the third year and was confined to the spacing of 0.085 m 2 /tree. Even after the fourth year of the experiment the pattern was confined to spacing from 0.046 to 0.291 m 2 /tree. The results suggest that there is an early phase of tree population growth during which the appearance of clusters of trees of fairly uniform size is promoted.

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