1 23 European Journal of Forest Research ISSN 1612-4669 Eur J Forest Res DOI 10.1007/s10342-020-01319-y European beech stem diameter grows better in mixed than in mono-specific stands at the edge of its distribution in mountain forests Hans Pretzsch, Torben Hilmers, Enno Uhl, Kamil Bielak, Michal Bosela, Miren del Rio, Laura Dobor, David I. Forrester, Thomas A. Nagel, et al.