Patch-level facilitation fosters high-Andean plant diversity at regional scales

Survey of the alpine vegetation in seven mountains of the Patagonian Andes from January to March of 2017 and 2018. On each mountain, we established one study site at each of three elevations (1600, 1800 and 2000 m). Accordingly, we sampled a total of 21 alpine plant communities (i.e., seven mountains x three elevations) dominated by cushion plants. At each community, 50 individual cushion plants were haphazardly selected within an area of approx. 0.5 ha, pairing each cushion with an adjacent non-cushion or open area 50 cm away in a random direction. In order to sample a similar surface in the surrounding open area, a wire hoop was shaped to match the size of the sampled cushion that was then placed on the ground. The number and identity of all plant species were recorded at both cushion and open area plots. Given that cushion plants are roughly elliptical, microsites were defined as elliptical plots, and thus, the longer and shorter axes of each cushion were measured as an approximate estimation of its area. In total, we sampled 2100 plots (1050 cushion plants and 1050 open area plots).