Forest Health Status in Hungary

Abstract

Because Hungary has about 18% forest area, it is not as densely forested as most of the countries in Europe. Forests are dominated by native species such as oaks, beech, hornbeam, and other broadleaves. As a result of an intensive afforestation in the last 50 years, introduced species, such as black locust, Scots pine, and improved poplars were widely planted and forest area increased by 50%—to 18 000 km 2. Several observations in Hungary from the early eighties detected an unusual amount and type of forest damage affecting native and introduced species. A shocking observation was the oak decline sweeping through the country with a dieback rate of 10 to 70% of the stems in the affected compartments within a decade. New methods had to be developed to detect and explain changes of forest health status and forest ecosystems. In close cooperation with the International Cooperative Program on the Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests), a national multi-level monitoring and research program was launched in 1986. The first level of the program—large scale monitoring—accepted defoliation and discoloration as key parameters, but a detailed survey of each sample tree was added. On the basis of the annual survey of about 22 000 trees, a significant increase of defoliation was observed. Although 79% of the trees were not defoliated in 1988, only 44% were fully foliated in 1995. Proportion of damaged trees (defoliation greater than 25%) seems to have stabilized at about 20% in the last 4 years, little lower than the average of the European survey results ranging from 7 to 59%. Oaks, black locust, and Scots pine were particularly heavily defoliated, while beech and hornbeam were only lightly affected. The disturbed balance of forest ecosystems is closely related to the lack of water—a result of river regulation since the 18th century and especially the 12-year period of dry and hot weather in the Carpathian Basin. Although SO 2 emission has been reduced by 50% since 1980 and NOx by 30% since 1987, and direct damages have not been largely observed, air pollution can be a predisposing factor of forest damages. Additional intensive research is necessary to clarify the role of climatic factors and air pollution effects on forest ecosystems, including direct effects, carbon and nutrient cycling at different sites, and damaging biotic factors.