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Abstract. Using an inter-disciplinary methodology, the paper aims to assess structural changes of the private forests restituted to their owners in early '90 in Romania (under the Law 18/1991), and to further estimate the economic rent resulted due to alternative management activities. The study area consists of restituted, private forests (799 ha) in Forest District Vama (North of the Romanian Eastern Carpathians). The forest structure dynamics was assessed by comparing initial forest structural characteristics at restitution (1990) , the used alternative being a minimum of 23 m 3 year -1 ha -1 harvested between 1990and 2004. In Romania, between 1994, the timber price significantly increased in comparison with the capitalization rate. Under these circumstances, the harvesting of forests immediately after restitution conducted to a total economic loss of about 9 million USD (present value -2014), compared with the alternative -maintaining the forest resources 20 years further. It is concluded that in Romania, the mismanagement of private forests restituted in '90s (Law 18/1991) resulted in direct economic losses for forest owners, of similar importance as the ecological consequences.

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The increasing worldwide interest in renewable energy and carbon storage has led to the development of relatively fast solutions to obtain wood biomass. The cultivation of fast-growing tree species in short-rotation crops, such as hybrid poplar clones, is one such solution, at least in temperate areas. Sometimes these monocultures are affected by disturbing factors, including severe insect defoliation, with strong destructive effects. The impact of defoliation on the growth and productivity of poplar crops is often estimated in the context of artificial defoliation. There have been few studies in which the effect of defoliation was calculated after natural defoliation. Among defoliating insect species, Clostera anastomosis L. is one of the most important defoliators of young poplars. This species developed severe defoliation in a 4-year-old poplar clone AF8 crop, from the northeastern part of Romania, in the spring and summer of 2017. The study aimed to assess the impact of defoliation both on the growth and mortality of defoliated trees and the productivity of the affected crop. To reach this goal, the height and radial growth of 150 trees with different defoliation rates (50 non-defoliated, 50 partially defoliated, and 50 completely defoliated) were measured and the defoliation symptoms and mortality were also evaluated for 4780 poplars (10% of the analyzed population). The defoliation caused a significant decrease in the annual height growth (28.6% of the partially defoliated trees and 38.5% of the completely defoliated trees) and a severe decrease in the radial growth, between 82.2% and 90.4%, respectively, depending on the defoliation rate. These strong decreases led to a significant decline in tree-level biomass accumulation, approximately 74.8% for partially defoliated trees and 83.1% for completely defoliated trees, for the year of defoliation. As a result, the loss in total biomass (for the four years of the rotation) was between 28.1% and 34.6%, respectively, depending on the defoliation rate. Therefore, the total biomass loss was 5 t·ha−1, representing approximately 70% of the forecasted production for 2017 only (approximately 7 t·ha−1).