Go or grow? Feedbacks between moving slopes and shifting plants in high mountain environments

Abstract

High mountains are climate change hotspots. Quickly rising temperatures trigger vegetation shifts such as upslope migration, possibly threatening mountain biodiversity. At the same time, mountain slopes are becoming increasingly unstable due to degrading permafrost and changing rain and snowfall regimes, which favour slope movements such as rockfall and debris flows. Slope movements can limit plant colonization, while, at the same time, plant colonization can stabilize moving slopes. Thus, we here propose that response of high mountain environments to climate change depends on a ‘biogeomorphic balance’ between slope movement intensity and the trait-dependent ability of mountain plants to survive and stabilize slopes. We envision three possible scenarios of biogeomorphic balance: (1) Intensifying slope movements limit vegetation shifts and thus amplify instability. (2) Shifting ecosystem engineer species reduce slope movement and facilitate shifts for less movement-adapted species. (3) Trees and tall shrubs shifting on stable slopes limit slope instability but decrease biodiversity. Previous geomorphic, ecological and palaeoecological studies support all three scenarios. Given differences in ecologic and geomorphic response rates to climate change, as well as high environmental heterogeneity and elevational gradients in mountain environments, we posit that future biogeomorphic balances will be variable and heterogeneous in time and space. To further unravel future biogeomorphic balances, we propose three new research directions for joint research of mountain geomorphologists and ecologists, using advancing field measurement, remote sensing and modelling techniques. Recognizing high mountains as ‘biogeomorphic ecosystems’ will help to better safeguard mountain infrastructure, lives and livelihoods of millions of people around the world.

Structural shifts in plant functional diversity during biogeomorphic succession: Moving beyond taxonomic investigations in an alpine glacier foreland

“…This high trait diversity offers beneficial effects for slope stabilization (Martin et al, 2010;Ohler et al, 2023;Zhu et al, 2015). At this point, the rates of geomorphic processes already decreased, resulting in reduced allogenic pressure (geomorphic disturbance, Eichel, Stoffel, & Wipf, 2023;Haselberger et al, 2021). This may be a result of autogenic factors, specifically ecosystem engineering (Osterkamp et al, 2012), species facilitation that allows the colonization of new species (Brooker et al, 2008;Corenblit et al, 2015;Wheeler et al, 2015) and an accelerated expansion in plant cover, which can be attributed to a more effective utilization of resources via niche differentiation (Díaz et al, 2007;Ravenek et al, 2014).…”

“…Incorporation of a trait-based approach has significant potential for advancing biogeomorphology (Larsen et al, 2020;Viles & Coombes, 2022). Previous studies in glacier forelands addressing the role of geomorphic processes in vegetation development have mainly focused on specific landforms and provided descriptive accounts of functional traits during stages of biogeomorphic succession (for a comprehensive overview, see Eichel, 2019;Eichel, Stoffel, & Wipf, 2023;Miller & Lane, 2018). With traits including clonal growth, burial tolerance, resprouting capacity and mat formation, Dryas octopetala L. has been recognized as an ecosystem engineer on lateral moraine slopes, influencing hillslope processes through sediment trapping, run-off reduction and moisture storage (Eichel et al, 2016).…”

“…Stabilization on lateral moraine slopes occurs stepwise in association with distinct species communities. These species communities, along with their traits and related on geomorphic processes, have been observed as common across ecosystems facing similar constraints (Eichel, Stoffel, & Wipf, 2023). Despite the identification of functional traits relevant for biogeomorphic succession, there is a notable research gap concerning the variability of trait diversity in vegetation communities throughout the biogeomorphic succession in glacier forelands.…”

Assessment and Mechanism Analysis of Forest Protection against Rockfall in a Large Rock Avalanche Area

“…In addition, in the village of Schneizlreuth in the Alps of Bavaria, Germany, rockfalls have occurred many times in recent years, posing a massive threat to roads and buildings in the region [14]. In recent years, studies have found that forests growing on mountain slopes have obvious protection and mitigation effects on rockfall disasters [15][16][17][18]. Currently, research on the protective effect of forests against rockfalls has been well verified in the mountainous regions of Europe, and some countries (e.g., Switzerland and France) have formulated afforestation policies to cope with rockfalls, 2 of 20 which have achieved good results [17,19,20].…”