The potential impact of climate change on the distribution of key tree species in Serbia under RCP4.5 and RCP 8.5 scenarios

The survival of forest tree species within certain areas of their distributions is in question due to the increasing occurrence of disturbances and degradation processes in forest ecosystems due to climate change. The aim of this paper is to predict changes in the spatial distribution of the ten most important tree species in Serbia (European beech, Pedunculate oak, Austrian oak, Hungarian oak, Sessile oak, Narrow-leafed ash, Silver fir, Norway spruce, Black and Scots pine) using climate indices (Forestry Aridity Index, FAI and Ellenberg Quotient, EQ) with up-to-date climate observations (E-OBS, covering the time period 1990-2019) and projections of future climate conditions (RCP 4.5 and RCP 8.5 scenarios, split into two time periods 2041-2070, 2071-2100). The computation of the area under the receiver operating characteristic (ROC) curves has shown that both FAI and EQ have a "fair" to "excellent" ability to predict the occurrence of five out of ten species (European beech, Silver fir, Norway spruce, Black and Scots pine), with EQ having a slightly better predicting ability. EQ-based projections from mid (2041-2070) to late 21st century (2071-2100) under RCP 4.5 predict that reduction rates will not exceed 25%. Similar reduction rates are given by FAI-based projections until 2070, while rates increase to approximately 35% towards the end of this century. For RCP 8.5, FAI-based projections are significantly worse than EQ-based projections. Irrespective of the used index, projections until 2070 suggest that 55-75% of existing habitats will remain intact. Towards the end of the century, however, our analysis indicate that 75-85% (EQ) to 90-100% (FAI) of the five analyzed species habitats, will be found outside of their current climate space.