Shifts in native tree species distributions in Europe under climate change

Key European tree species are expected to contract their ranges under changing climate, thus there is a need to assess range shifts for other native tree species that could fill their forest niche. Recent studies have focused on economically important species, revealing a wide range of shifts in their distribution worldwide and highlighting several pathways for potential future changes. We aimed to quantify changes in projected ranges and threat levels by the years 2041-60 and 2061-80, for 20 European temperate forest tree species under four climate change scenarios. We compared ten standard stock tree species with ten alternative stock species, that are less frequent and less preferred by managers. We combined distribution data from several sources for each tree species and developed species distribution models using MaxEnt and seven bioclimatic variables. We applied these models to projections of future climate from four global circulation models, under four Shared Socioeconomic Pathways and for near and middle terms: 2041-60 and 2061-80. We also assessed the relationships between predicted range contraction and their functional traits. Analysis of MaxEnt models divided the studied tree species into three groups: non-threatened (Sorbus torminalis, Ulmus minor, Tilia platyphyllos, Acer pseudoplatanus, Prunus avium, and Carpinus betulus), partially threatened (U. laevis, Betula pendula, Quercus robur, Q. petraea, A. platanoides, Fagus sylvatica, Fraxinus excelsior, T. cordata, Alnus glutinosa, and U. glabra), and the most threatened (Abies alba, Larix decidua, Picea abies, and Pinus sylvestris). For the last group, almost half of the range contraction will occur earlier (2041-2060) compared to our previous predictions (2061-2080). The proportion of range contraction decreased with increasing specific leaf area, leaf area, leaf nitrogen content, seed mass, and specific stem density while it increased with increasing height. Our study provides novel predictions of shifts in climatic optima under the most recent climate change scenarios, which would be useful for evidence-based conservation and management of European forests. The near-term predicted threats to the main standard stock tree species call for intensified preparation for incoming changes. We recommend splitting the silvicultural risks over a wider range of tree species, also including alternative stock species.