FORESTRY IDEAS, 2011, vol. 17, No 1 (41) NATURAL DISTURBANCE HISTORY OF THE PRISTINE PICEA ABIES FOREST PARANGALITSA Momchil Panayotov 1,2 , Dominik Kulakowski 3 , Heinrich Spiecker 4 , Frank Krumm 2 , Lucinda Laranjeiro 5 and Peter Bebi 2 1 University of Forestry, Sofia, Bulgaria. E-mail: mp2@abv.bg 2 WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland. 3 Clark University, USA. 4 Institute for Forest Growth, University of Freiburg, Germany. 5 WSL Swiss Federal Institute for Forest, Snow and Landscape Research, Birmensdorf, Switzerland. UDC 574.4 Received: 03 August 2010 Accepted: 07 July 2011 Abstract Although understanding natural disturbance regime is very important for the management of subalpine coniferous forests, studies for Southern European Mountain ecosystems are still scarce. Among the reasons are difficulties in finding unmanaged forests that could serve as reference. We studied the disturbance history of an old Norway spruce-dominated forest in the “Parangalitsa” biosphere reserve in Bulgaria. It was declared a reserve in the 1930 s , but was protected from human intervention before that. We used aerial photo interpretation to detect disturbance areas and dendroecological methods to date the occurrence moment of the disturbance events. Over the past 150 years windthrows have been the main type of disturbance. About 20 percent of the forested area was subjected to complete blowdown. The largest proportion of the affected territory was due to medium sized windthrows with dimensions of 1 to 10 ha. Although Ips typhographus populations were large enough to cause mortality of some live trees, the populations did not grow to epidemic proportions. Fire disturbance was of limited importance and only two areas (4 percent of the study area) showed evidence of fire in the 20 th century. The forest ecosystem in Parangalitsa has high resilience, which is probably due to the high landscape heterogeneity of forest structures and continuous interaction between natural disturbances. Key words: Bulgaria, natural disturbances, Picea abies, windthrow. Introduction Disturbances are among the key proc- esses that guide forest dynamics. They affect forest structure, compo- sition, patchiness and resource avail- ability (Oliver and Larson 1990, Laska 2001). To enable a real understand- ing of forest dynamics within a given ecosystem, their role on biodiversity and thus justify adequate forest eco- system management, thorough knowl- edge of local natural disturbance regime is needed (Veblen et al. 1994, Schütz