Potential elevation shift of oriental beech (Fagus orientalis L.) in Hyrcanian mixed forest ecoregion under future global warming

Abstract

Iran's Hyrcanian forests cover a relatively narrow strip in the north part of Iran, which are among the most important and valuable ecosystems registered in UNESCO's World Heritage List. Although there are worries about the impact of climate change, the influences of this issue on tree species in the Hyrcanian forest less studied. The effect of climate change on species distribution usually results in species shifting to higher altitudes and latitudes. In this study, the effect of climate change on the elevation shift of oriental beech as one of the most abundant and important tree species of the Hyrcanian forests was investigated, using an ensemble species distribution model for the current year, 2050, and 2070 under different climatic scenarios. Totally, 1092 occurrences of the beech were recorded for constructing the models. Results showed the mean elevation of the beech at the current climate conditions was 1110 m, which will be shifted to higher altitudes. The mean elevation distribution under RCP2.6, 4.5, 6.0, and 8.5 were 1210 m, 1279.2 m, 1280 m, and 1340 m for the year 2050; for the year 2070, they were 1190 m, 1370 m, 1340 m, and 1460.2 m. As a result, the species will shift to higher altitudes under the future climate change. The predicted potential distributions suggested that the most suitable areas for oriental beech at the current climate conditions are in the center (Mazandaran province) and west (Guilan province). Because of climate change, high potential habitats for the beech will shift from east to west that can provide a vision into the availability of suitable areas for the species regeneration and reforestation programs.