“…Seedling establishment is a demographic bottleneck to regeneration beyond current treelines; although the establishment and survival of seedlings is an obvious precursor to the presence of mature trees, they are also very sensitive to environmental conditions and mortality can be extremely high among young tree seedlings (Alexander, 1987;Germino, Smith, & Resor, 2002). In particular, limitations to establishment beyond the treeline have been attributed to the long time periods required for trees to reach reproductive maturity (Aitken, Yeaman, Holliday, Wang, & Curtis-Mclane, 2008), the variable importance of interspecific interactions with other plant species (Loranger, Zotz, & Bader, 2017;Maher, Germino, & Hasselquist, 2005), the effects of predation and herbivory on tree seeds and seedlings (Brown & Vellend, 2014;Kambo & Danby, 2017;Urli, Brown, Perez, Chagnon, & Vellend, 2016) and the effects of microclimate extremes (Renard, Mcintire, & Fajardo, 2016;Rundel et al, 2014). Importantly, these key factors do not act in isolation from one another, and studies of establishment dynamics should therefore attempt to consider their effects simultaneously.…”