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Economic analysis of even-aged fir stand management was illustrated using the example of the forests of the Croatian Dinaric region, as well as their transformation into more stable unevenaged structures. Two scenarios (even- aged, uneven-aged) were simulated against the backdrop of the existing forest stand structure of future forest stand management during a 140- year period using forest growth modeling software MOSES version 3.0 in order to identify economic differences amongst different scenarios both at stand level and at forest level. The research included forest management analysis throughout the transformation period and subsequently the continuation of balanced state forest management. Moreover, the research also provided the opportunity of forest purchase within the price range from 1000 to 12, 500 EUR/ha, amid assumed fluctuation of selling prices of timber assortments throughout the simulation period. Discount rates from 1% to 5% were used during the economic analysis. The research findings showed that, according to harvesting costs, Net Present Value and Internal Rate of Return, uneven-aged forest management system, including the transformation period, achieved superior economic results, albeit at discount rates that exceeded 1.24%. The conclusion was reached that, according to all economic criteria, uneven-aged mixed silver fir-beech management system is preferred compared with the pure even-aged silver fir management.

Background and Purpose: Regeneration and conversion of pure spruce plantations is a very important task for forest management in Europe. This subject is less marked in Croatia in view of the fact that in Croatia there are only 75, 000 ha of pure coniferous plantations, which are raised on unstocked forest land. In Croatia, no investigation has yet been carried out on the development of the stand structure, succession processes of autochthonous species and methods of reforestation and conversion of spruce plantations. This study is one of the first which deals with the aforementioned problems. Materials and Methods: Since 1956 five successive measurements (d b h and tree heights, tree-crown diameters, height of crown base, condition and position of a tree, horizontal crown projections, density and structure of regeneration, comparison of chemical and physical characteristics of soils between the plantation, natural stand and meadow) have been performed in a 161-year-old spruce plantation on a permanent experimental plot (1 ha), in which no silvicultural treatments were carried out during the last 42 years. Results and discussion: The period of the last 42 years, during which there were no management interventions in the stand, is characterised by the specific development of the stand structure. The fact is that in the old Norway spruce plantation there was a considerable potential for succession of autochthonous European beech and silver fir, at the time of the first measurement in 1956. However, in spite of two thinnings performed at the beginning of the 48-year long period (66 Norway spruce trees per ha) and 110 naturally cleared (removed) spruce trees during the last 42 years (self-thinning), the processes of beech and fir succession were very slow. Conclusions: The results obtained of slowed down development of the stand structure of an old spruce plantation, and slowed down succession processes, related to the absence of management interventions and delayed regeneration, are discussed in accordance with the results of spruce plantation management in Central Europe. Further investigations are necessary of the old spruce stand in two directions ; under regime without silvicultural treatment (natural development) and under regime by different silvicultural methods.