engleski

Management models applied to fir forests in Gorski Kotar

Fir forests in Gorski kotar have been managed with different models, the majority of which are derived from the normal mathod.Models resulting from the Normal Method Before and After Cutting(precribed by the Instructions of 1903), as well as Klepac`s"New System of Managing Selection Forests" and the Institute`s(ecological-management types), have been used since the beginning of management with these forests.Its clear from the position of tree number curves in "old" normal models(which represnt the correction of the condition in the forest) and in the nomal model of the studied EGT I-C-10b in relation to adequate Klepac`s normal models that in the majority of old models the curve of tree number is above Klepac`s curve, with more significant deviations occurring(in%)in lower and higher diameter classes.This is the consequence of the condition of these forests at the time of management(the end of the nineteenth and the first several decades of the twentieth century), when these forests contained excessive growing stock resulting from extensive management. One part of these models was constructed under an unrealistic assumption that the basal areas of all diameter classes were equal. It is for this reason that the deviation of these models from the model by Klepac is the most distinct the lowest diameter classes.It is interesting that the deviation in percentages of the Institute`s normal model EGT I-C-10b, adjusted to pure fir codition before cutting, almost completely coincides with Jovanovac` normal model for the land community Benkovac from 1912.This model was made under the assumption of the equality of basal areas of all diameter classes.Furthermore, within this EGT, represented by one model, there were stands with a wide range of quality classes, fir I/II-IV and beech II-IV.Basedon these facts, the use of original Klepac`s normal models is recommended formanaging fir selection forests.Inthis way, an artificial lowering of the heights of dominant trees(the result of cutting the trees above a certain maturity dimension and different ways of defining dominant heights used by some authors)will be avoided(Božić&Čavlović 2001).Based on the position of the curves of the tree numbers from different years of measurement and on their position towards the proposed model, it is possible to draw conclusions on the condition of stand`s managed status and to determine the trends of a given stand in relation to the proposed model.This, along with the record of the completed activities, may greatly assist in the future management of these stands.The proposed model by Klepac should be regarded as a transitional model rather than a permanent one until a more favourable model is found through management activities.

Gorski Kotar ; forest management ; models

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