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

Glacier forelands are among the most rapidly changing landscapes on Earth. Stable ground is rare as geomorphic processes move sediments across large areas of glacier forelands for decades to centuries following glacier retreat. Yet, most ecological studies sample exclusively on stable terrain to fulfil chronosequence criteria, thus missing potential feedbacks between geomorphic disturbances and vegetation colonization. By influencing vegetation and soil development, such vegetation-geomorphic disturbance feedbacks could be crucial to understand glacier foreland ecosystem development in a changing climate. We surveyed vegetation and environmental properties, including geomorphic disturbance intensities, in 105 plots located on both stable and unstable moraine terrain in two geomorphologically active glacier forelands in New Zealand and Switzerland. Our plot data showed that geomorphic disturbance intensities changed permanently from high/moderate to low/stable when vegetation reached cov..., 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, ...,