Data from: Density-dependent species interactions modulate alpine treeline shifts

Species interactions such as facilitation and competition play a crucial
role in driving species range shifts. However, density-dependence as a key
feature of these processes has received little attention in both empirical
and modelling studies. Herein, we used a novel, individual-based treeline
model informed by rich in-situ observations to quantify the contribution
of density-dependent species interactions to alpine treeline dynamics, an
iconic biome boundary recognized as an indicator of global warming. We
found that competition and facilitation dominate in dense versus sparse
vegetation scenarios, respectively. The optimal balance between these two
effects was identified at an intermediate vegetation thickness where the
treeline elevation was the highest. Further, treeline shift rates
decreased sharply with vegetation thickness and the associated transition
from positive to negative species interactions. We thus postulate that
vegetation density must be considered when modeling species range dynamics
to avoid inadequate predictions of its responses to climate warming.