An unusually high shrubline on the Tibetan Plateau.

The genus Juniperus, composed of ca. 76 species, has a broad altitudinal distribution over the northern Hemisphere (Adams 2014). For instance, some juniper shrub species grow in coastal sites (Garcia-Cervigon et al. 2019) whereas others grow in alpine regions at ˃5,000 m a.s.l. in the Himalayas (Huang et al. 2019, Lu et al. 2019). In the so-called 'Third Pole' region, Juniperus species form some of the highest alpine treelines worldwide (ca. 4,900 m a.s.l.) and survive in harsh environments on poor rocky soils (Miehe et al. 2007, Lyu et al. 2019). Juniperus trees and shrubs at their upper distributional margins ("treeline" and "shrubline", respectively) likely experience the highest warming rates of all junipers and are recognized as sensitive ecological indicators of responses of land ecosystems to shifting abiotic and biotic conditions (Korner 2012). Accordingly, treelines and shrublines are especially suited for long-term ecological studies as they are easily relocated over time. However, the upper altitudinal limit of Juniperus and its cause(s) remain unknown.