Similar vegetation-geomorphic disturbance feedbacks shape unstable glacier forelands across mountain regions

In the Mueller glacier foreland, we surveyed 55 plots with 125 species in total in February 2018, using the smartphone-based VegApp (www.vegapp.de) to note field observations. In the Turtmann glacier foreland, we surveyed 50 plots with 121 species in total in July and August 2015 using a paper-based survey. We visually determined individual species cover, as well as tree, shrub, herb, bare ground and total cover (Appendix S1: Table S2). Our survey focused on vascular plants, however, we included two prominent Racomitrium moss species with dominant cover (up to 90%) in the Mueller glacier foreland (cf. Burrows 1973). In the Turtmann glacier foreland, moss cover was < 10% and not included in further analyses. Nomenclature follows Lauber and Wagner (2018) for Turtmann and Breitwieser et al. (2010) for the Mueller glacier foreland. Based on our observations of visible landforms and active sediment transport, we noted which geomorphic processes (gullying, debris flow, interrill erosion, debris sliding, wind erosion, wash, cryoturbation, solifluction) disturb or recently disturbed plot vegetation (Fig. 1c, Table 1). Using known magnitude and frequency for identified geomorphic processes in general (Rapp 1960, Flageollet 1996, Otto and Dikau 2004) and on moraine slopes (Curry et al. 2006, Woerkom et al. 2019), we assigned a geomorphic disturbance intensity to each plot based on the most intense geomorphic process that disturbed the plot (Table 1; Eichel et al., 2016). Thereby, geomorphic disturbance intensities became comparable across glacier forelands.