Prediction of the European beech (Fagus sylvatica L.) xeric limit using a regional climate model: An example from southeast Europe

Ellenberg's climate quotient (EQ), which is a simple biometeorological index, was used to predict the xeric limit of the European beech distribution and potential future changes in Serbia (southeast Europe). The general aim of this study was to evaluate EQ as a predictive tool of the xeric limit of the beech at the southern edge of its distribution and to predict future changes in the xeric limit. The novelty of this study is its assessment of EQ accuracy for Serbia, the beech populations of which were separated from Central European refugia during the last glacial period. Climate projections from the coupled regional climate model EBU-POM were used to predict the changes in the xeric limit in the 21st century. The computation of the area under the receiver operating characteristic curves showed that EQ had “good” and “fair” predictive ability for two samples. Using three threshold criteria and different samples, the beech xeric limit in Serbia for the reference period of 1961–1990 varied between EQ values of 20.1 and 29.5. Significant changes in the beech xeric limits were predicted for the 21st century. The EQ calculations for 2001–2030 (A1B scenario) predicted that more than 20% of the present-day beech forests will be located outside of the ideal bioclimatic niche characterised by EQ ≤ 30 that was proposed by Ellenberg. For 2071–2100 (A1B and A2 scenarios), up to 90% of the current beech forests are expected to be located outside of that niche, and approximately 50% will be located beyond the limit EQ = 40 for which beech mass mortalities have been observed. The results suggest an urgent need for the development of adaptive forest management strategies for beech in this region.