Conditions for feedbacks between geomorphic and vegetation dynamics on lateral moraine slopes: a biogeomorphic feedback window

Abstract

Little Ice Age lateral moraines represent one of the most important sediment storages and dynamic areas in glacier forelands. Following glacier retreat, simultaneous paraglacial adjustment and vegetation succession affect the moraine slopes. Geomorphic processes (e.g. debris flows, interrill erosion, gullying, solifluction) disturb and limit vegetation development, while increasing vegetation cover decreases geomorphic activity. Thus, feedbacks between geomorphic and vegetation dynamics strongly control moraine slope development. However, the conditions under which these biogeomorphic feedbacks can occur are insufficiently understood and major knowledge gaps remain. This study determines feedback conditions through the analysis of geomorphic and vegetation data from permanent plots in the Turtmann glacier foreland, Switzerland. Results from multivariate statistical analysis (i) confirm that Dryas octopetala L. is an alpine ecosystem engineer species which influences geomorphic processes on lateral moraines and thereby controls ecosystem structure and function, and (ii) demonstrate that biogeomorphic feedbacks can occur once geomorphic activity sufficiently decreases for D. octopetala to establish and cross a cover threshold. In the subsequent ecosystem engineering process, the dominant geomorphic processes change from flow and slide to bound solifluction. Increasing slope stabilization induces a decline in biogeomorphic feedbacks and the suppression of D. octopetala by shrubs. We conceptualize this relationship between process magnitude, frequency and species resilience and resistance to disturbances in a 'biogeomorphic feedback window' concept. Our approach enhances the understanding of feedbacks between geomorphic and alpine vegetation dynamics on lateral moraine slopes and highlights the importance of integrating geomorphic and ecological approaches for biogeomorphic research.

Monitoring and reconstructing past biogeomorphic succession within fluvial corridors using stereophotogrammetry

“…Past biogeomorphic succession dynamics can thus be quantified within fluvial corridors, and potentially also in different biogeomorphic ecosystems such as salt marshes, mangroves, coastal dunes and also mountainous hillslopes (Eichel et al, 2016). These archives can potentially be used to develop vegetation height models ranging from the establishment of cohorts until the adult stage, and to derive accurate growth curves for riparian woody species which interact with fluvial morphodynamics, e.g.…”

Geomorphological processes and frozen ground conditions in Elephant Point (Livingston Island, South Shetland Islands, Antarctica)

“…Solifluction processes are widespread on the moraine, though with minor landforms associated. The movement of the unconsolidated sediments on the moraine disturbs vegetation development (Eichel et al, 2015).…”

Short-term geomorphological evolution of proglacial systems

“…Recently, there has been a realisation that the assumption of a succession of vegetation or soil types is rather more complicated than this simple conceptual model and interactions of soil formation, vegetation development and geomorphological activity have become a new focus (Eichel et al, 2013(Eichel et al, , 2015Temme and Lange, 2014;d'Amico et al, 2014;Temme et al, 2016).…”

“…Then non-metric multidimensional scaling can be used to facilitate comparisons between groups, cf. Eichel et al (2013Eichel et al ( , 2015. (Table 2), but a SfM-derived DEM can be compared DEM from another source, such as ALS (e.g.…”

“…Heckmann et al, 2016a and references therein). This recent increase in attention is due to a growing realisation that these landscapes exhibit a range of properties that make them a highly relevant subject of study: First, they are unique natural laboratories where the successional development of soil and vegetation can be investigated; recent studies emphasise the interaction of soil and vegetation development and geomorphological dynamics (Temme and Lange, 2014;Eichel et al, 2013Eichel et al, , 2015Temme et al, 2016). Second, due to the high rates of geomorphological activity, they form an ideal location for the application of mapping and measurement methods to document and quantify changes, and to test models,…”