DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 7-8/1973 str. 15 <-- 15 --> PDF |
Summary CORRELATION ANALYSES OF HEIGHT INCREMENT, HEIGHT, DIAMETER B. H. AND DIAMETER INCREMENT IN CERTAIN STANDS OF SILVER FIR In stands of Silver Fir belonging to the forest communities of Blechno-Abietum Horv. (Forest Districts Sušica and Tuški Laz) and Fagetum abietetosum Horv. (Forest District of Toričak) in the Gorski Kotar Reg on (Croatia) there were taken measurements of felled Fir trees. In each tree were measured: diameter b. h. (di,a = 1), total height (h = 2), diameter increment of the last five years (ia5 = 3), diameter increment of the penultimate five years (ijdo-s) = 4), height increment of the last five years (ihs = 5) and height increment of the penultimate five years (ih(10 5) = 6). There vere measured a total of 755 Fir trees, of which 231 in the Forest District of Sušica, 268 in Tuški Laz and 256 in Toričak. The diameter increment was established by using the Pressler borer, while the height increment with a tape by measuring distances between whorls. On the basis of measured magnitudes the author wished to establish the degree of the connection of the mentioned variables in various different Fir stands and to find out a favourable combination of available variables on the basis of which it would be possible to perform an assessment of height increment. In addition to the mentioned six variables there was also taken into computation the average annual diameter increment of a 10-year period (i,jio = 7) and the average annual height increment of a 10-year period (ihio = 8). Through the correlation analysis the author computed the linear partial and multiple correlation coefficients under the assumption that the studied population possesses a mult.variable normal distribution. Data processing was performed on an electric computer of the CAE 90—40 type. Because of the volume of the material in Tables the author presents — according to his opinion — the interesting partial (Tabs. 1—4) and multiple (Tab. 5) correlation coefficients. Testing of significance was performed by means of the null hypothes s and the Z-transformation by R. A. Fisher. Although in the correlation analysis it is not possible to determine which is a dependent variable and which not, the author considered the height increment primarily a dependent variable because he was interested in the assessment of height increment. Correlation between the height increment and diameter b. h., as between the height increment and height was very weak or almost absent in all the three forest districts irrespective of which order of correlation coefficients was in question. Only in the Forest District of Sušica the partial coefficients of the first order — under the exclusion of the influence of diameter increment — were of medium strength (Tab. 1). The height increment of the last and penultimate five years exhibited a strong connection in the Forest District of Sušica and Tuški Laz, while in the Forest D strict of Toričak this connection was very weak (Tab. 2). The correlation between the height increment and diameter increment in all three forest districts was positive: in the Forest District of Sušica medium, in Tuški Laz weak, in the Forest District of Toričak a very weak correlation only between the height increment and diameter increment of the last five years; other partial correlation coefficients in the Forest Distr ct of Toričak were not signnificantly different from zero (Tabs. 3 and 2). The diameter increment and diameter b. h., as the diameter increment and height were in a significant correlat on in all three forest districts (Tab. 4). However, under the exclusion of the influence of diameter b. h., there was no correlation between the diameter increment and height in the Forest D´stricts of Tuški Laz and Toričak, while in the Forest District of Sušica this connection existed between the 95- and 99-percent limit of significance. There was also no correlation between the diameter increment and diameter b. h. under the exclus:on of height in the Forest District of Sušica, while in the Forest Districts of Tuški Laz und Toričak it did exist. Multiple correlation coefficients between the height increment, diameter b. h. and heights were very small in the Forest Districts of Sušica and Toričak, while in the Forest D strict of Tuški Laz they were insignificant (Tab. 5). The height increment exhibited the best correlation with the diameter increment and with other factors associated with the diameter increment. Multiple correlation coeff cients between the height increment, diameter b. h. and diameter increment respectively, or between the height increment, diameter increment and |