In the mutual struggle for survival in forest stands it is a normal phenomenon that individual trees dieback and are through regular silvicultural work removed from the stands. However, a rather serious, large- scale dying back of pedunculated oak in some European countries (Rumania, USSR) and the USA was observed at the beginning of this century, and some twenty years ago massive dying back of this species was also noted in Yugoslavia. The phenomenon has taken such proportions that in individual regions entire forest management units have been affected, so that local foresters are compelled in an unplanned way to meet the annual felling quotas from such forests, i.e. from died-back trees. In Yugoslavia there are about 2,5 milion hectares of land under pure and mixed pedunculated oak stands whose standing timber together with sessile-flowered oak totals almost 100 million cu.m., and whose annual volume increment amounts up to 3 million cu.m. of high-quality growing stock of great national value. This has caused serious concern among forest specialists, who have immediately started scientifically to investigate the causes of this phenomenon. We have, on our part, begun to study the economic consequences of the dieback of oak woods in Jugoslavia. The results of one of our investigations of this kind are presented in this paper too. For this investigation we selected 44 pedunculated oak stands in the Socialist Republic of Croatia and arranged them into 22 pairs of stands of the same age, fertility class habitat and the same mode of management. In each of these pairs one stand was regularly completely health and the other seriously affected by the dieback. According to an especially devised methodology, we measured all relevant data to arrive at the necessary conclusions regarding the economic consequences of the dieback of oak forests. On the basis of only two pairs of the investigated stands, aged 68 and 126 years respectively, and on the basis of data presented in table 8 of this paper, we can conclude as follows: 1. The average quality of standing timber in the younger pedunculated oak stands (68 years) affected by the dieback was 13,7 percent and in the ripending stands (126 years) even 40,2 percent below the average quality of healthy stands (table 1). 2. Diameter increment of standing timber in the younger stands (68 years) affected by the dieback was bu 13,7 percent and in the ripening ones by 21,6 percent smaller than in the same but healthy such stands (table 2). As a result, the younger stands afftected by the dieback lagged behind the healthy ones by 4 years, and the ripening ones by even as much as 12,7 years (table 2). 3. The percentage of sapwood in the investigated assortments amounted to 23,5 percent (table 3). In dieback- affected stands sapwood first begins to decay or rots away in 2 to 3 years, which must for this reason .....
