UNFAVORABLE CLIMATIC FACTORS AND THEIR IMPACT ON THE DECLINE OF SPRUCE AT THE KOPAONIK NATIONAL PARK (CENTRAL SERBIA)

The paper presents the results of research on the influence of natural (biotic and abiotic) factors on the decline of spruce [Picea abies (L.) Karst.] at the Kopaonik National Park (Republic of Serbia), in the period from 2010 to 2019. As an indicator of the influence of unfavorable climatic factors on the decline of forests in the Kopaonik National Park, the share of random yields of wood volume in the total allowable cut, resulting from the overpopulation of bark beetles, was determined. In order to understand the causes of decline, a sample plot, located in pure spruce stand older than 60 years in the northwest exposure and at the altitude of 1720 m, was used to monitor and assess the impact of air pollution and its effects on forest ecosystems. Furthermore, the data on temperatures and precipitation amounts during the year and in the vegetation period were analyzed in order to understand and connect the influence of unfavorable climatic factors with the decline of trees more clearly. A comparison was made between tree mortality, when occurred, with the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) as the most commonly used indicators for monitoring drought. It was stated that the decline of trees was initiated by the influence of unfavorable climatic factors during three consecutive years (2011-2013), accompanied with snowstolins during the winter of 2012, which created favorable conditions for overpopulation of bark beetles as secondary pests. As a result, one of the largest deforestations was recorded on the territory of the Kopaonik National Park. These results indicate that changes in precipitation and air temperature, whose deviations from the decade long average have been occurring regularly for several years, have significantly weakened the vitality of trees, and thus increased their predisposition to the increase of already present bark beetles.