· 1 INTRODUCTION. Mountain species and habitats are expected to be particularly sensitive to ongoing global change (IPPC, 2013; Krajick, 2004; Steinbauer et al., 2018).Tree line ecotones, that are, the transition zones between the upper limit of closed forest (timberline) and the treeless alpine grasslands (Körner, 2012), are particularly diverse and dynamic habitats (, Camarero et al., 2015).