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ŠUMARSKI LIST 5-6/2016 str. 48     <-- 48 -->        PDF

approximately equal values of statistical indicators. The values of R2 of all the studied models range from 0,65 to 0,82.
In order to further evaluate the proposed models, their visual comparisons in the form of performances in Figure 1 were also carried out. Furthermore, anamorphic site index curve was calculated for each reported model to determine the age and the value of the current height increment at the time of culmination and thus assess the consistency of the model regarding the real situation in the field.
The obtained results indicate that current height increment culminates at the age of 21 (Korsun’s model), 25 (Korf’s and Schumacher’s model), 29 (Champan-Richards’ model) and 37 (Todorović’s model). Hossfeld IV function proved to be the most unfavorable, with different culmination times and values which is the result of limiting the curve to pass through the desired point or height at the age of 100 (site index).
Although Korsun’s and Schumacher’s models gave very similar fits, Korsun’s equation (a little better overall statistics than that for the Schumacher’s one) was chosen as the most appropriate model to assess dominant height-age relations. The performed site index curves according to Korsun’s models are presented in Figure 2.
All modeled function parameters of Korsun’s equation are statistically significant. According to the implemented model, the current annual height increment culminates at the age of 21 and the values of the current annual height increment at this age vary from 0,45 m for SI32 to 0,22 m for SI16 (the bottom right corner of Figure 2). The lowest value of SI100 is 16 m, while the highest one is 32 m. There are three site classes between these values and the study area has a total of 5 site classes. The difference of 4 m between site index values represents approximately the average standard deviation of the values from the regression line for the age class 100 (90-110).
The optimum utilization of the production capacity of forest communities and forest tree species related to a specific site conditions is of crucial importance for successful