Similar vegetation-geomorphic disturbance feedbacks shape unstable glacier forelands across mountain regions
Eichel, Jana; Draebing, Daniel; Winkler, Stefan; Meyer, Nele
(2023) Ecosphere, volume 14, issue 2, pp. 1 - 18
(Article)
Abstract
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 fulfill chronosequence criteria, thus missing potential feedbacks
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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 permanently changed from high/moderate to low/stable when vegetation reached cover values of around 40%. Around this cover value, species with response and effect traits adapted to geomorphic disturbances dominated. This suggests that such species can act as “biogeomorphic” ecosystem engineers that stabilize ground through positive feedback loops. Across floristic regions, biogeomorphic ecosystem engineer traits creating ground stabilization, such as mat growth and association with mycorrhiza, are remarkably similar. Nonmetric multidimensional scaling revealed a linked sequence of decreasing geomorphic disturbance intensities and changing species composition from pioneer to late successional species. We interpret this linked geomorphic disturbance-vegetation succession sequence as “biogeomorphic succession,” a common successional pathway in unstable river and coastal ecosystems across the world. Soil and vegetation development were related to this sequence and only advanced once biogeomorphic ecosystem engineer species covered 40%–45% of a plot, indicating a crucial role of biogeomorphic ecosystem engineer stabilization. Different topoclimatic conditions could explain variance in biogeomorphic succession timescales and ecosystem engineer root traits between the glacier forelands. As glacier foreland ground is widely unstable, we propose to consider glacier forelands as “biogeomorphic ecosystems” in which ecosystem structure and function are shaped by geomorphic disturbances and their feedbacks with adapted plant species, similar to rivers and coasts.
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Keywords: biogeomorphic ecosystem, biogeomorphic succession, biogeomorphology, chronosequence, critical zone, ecogeomorphology, ecosystem engineering, geomorphic disturbances, glacier forefield, paraglacial processes, plant traits, vegetation succession
ISSN: 2150-8925
Publisher: Wiley
Note: Funding Information: This study was funded through a research grant by the Hanna Bremer Foundation and a research grant by the German Research Foundation (BIMODAL, DI 414/22-1). We thank G. Fitzgerald for acquiring and organizing our trait data, D. Hedding and T. Kattenborn for help with an Uncrewed Aerial Vehicle survey in Mueller glacier foreland, S. Schmidtlein for providing a first VegApp version and advice on isopam, I. Wieland for elemental analyses, and M. Kleinhans for comments on earlier versions of this manuscript. We acknowledge and thank the TRY initiative and database hosted, developed, and maintained at the Max Planck Institute for Biogeochemistry by J. Kattge and G. Bönisch. Permission to work in Mueller glacier foreland was kindly granted by the Department of Conservation, New Zealand (concessions 63969-AIR and 63884-RES). Vehicle access to Turtmann glacier foreland was kindly permitted by the GOUGRA AG. We thank several anonymous reviewers for their helpful comments on improving this manuscript. Funding Information: This study was funded through a research grant by the Hanna Bremer Foundation and a research grant by the German Research Foundation (BIMODAL, DI 414/22‐1). We thank G. Fitzgerald for acquiring and organizing our trait data, D. Hedding and T. Kattenborn for help with an Uncrewed Aerial Vehicle survey in Mueller glacier foreland, S. Schmidtlein for providing a first VegApp version and advice on isopam, I. Wieland for elemental analyses, and M. Kleinhans for comments on earlier versions of this manuscript. We acknowledge and thank the TRY initiative and database hosted, developed, and maintained at the Max Planck Institute for Biogeochemistry by J. Kattge and G. Bönisch. Permission to work in Mueller glacier foreland was kindly granted by the Department of Conservation, New Zealand (concessions 63969‐AIR and 63884‐RES). Vehicle access to Turtmann glacier foreland was kindly permitted by the GOUGRA AG. We thank several anonymous reviewers for their helpful comments on improving this manuscript. Publisher Copyright: © 2023 The Authors. Ecosphere published by Wiley Periodicals LLC on behalf of The Ecological Society of America.
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