Biogeomorphic interactions in the Turtmann glacier forefield, Switzerland Jana Eichel a, ⁎, Michael Krautblatter b , Sebastian Schmidtlein c , Richard Dikau a a Department of Geography, University of Bonn, Meckenheimer Allee 166, 53115 Bonn, Germany b Engineering Geology, Technical University München, Arcisstrasse 21, 80333 München, Germany c Department of Geography and Geoecology, Karlsruhe Institute of Technology, Kaiserstraße 12, 76128 Karlsruhe, Germany abstract article info Article history: Received 3 December 2012 Received in revised form 12 June 2013 Accepted 14 June 2013 Available online xxxx Keywords: Biogeomorphology Geomorphic activity Vegetation succession Biogeomorphic succession Geomorphic-engineer species Paraglacial Glacier forefields are dynamic environments dominated by active paraglacial processes and simultaneous veg- etation succession, triggered by glacier retreat since the Little Ice Age. While these dynamics are accelerating in the last decades owing to climate change, interactions between vegetation and geomorphic processes and components and the resulting patterns are only partly understood. Using a biomorphic approach based on preexisting geomorphic and glaciological data, geomorphic activity was classified and mapped in the Turtmann glacier forefield, Switzerland. Vegetation and environmental parameters were sampled. Vegetation analysis was subsequently carried out with vegetation classification and ordination for identifying relation- ships to environmental parameters. A paraglacial impact on vegetation succession could be shown and differ- entiated according to geomorphic activity on constant terrain age. Biogeomorphic concepts were then applied to explain these patterns. Three biogeomorphic succession phases were identified and related to degrees of activity, species composition, and strength of interactions. Integrating our results into the paraglacial concept, we show how the paraglacial adjustment of a glacier forefield is significantly affected by biogeomorphic interactions. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Since the late nineteenth century, glacier forefields have been a key research interest for geomorphologists, ecologists, and biologists (Coaz, 1887; Poser, 1932). Their continuous ecological and geomor- phological change is conditioned by the ongoing stepwise glacier retreat since the end of the Little Ice Age (LIA) and its recent accel- eration in the last decades (Paul et al., 2004). Dynamics of glacier re- treat steadily expand the space for active geomorphic processes as well as vegetation colonization and succession. 1.1. Paraglacial glacier forefield systems As unvegetated valley-floor deposits are exposed to erosion, they undergo paraglacial modification by mass movements, frost sorting, and wind and water transport (Ballantyne, 2005). Lateral moraines are especially prone to paraglacial sediment reworking, e.g., through slope failure, surface wash, and debris flows, which are considered to be the dominant agents (Ballantyne, 2002a). Occurring glaciofluvial processes within the glaciofluvial subsystem also contribute strongly to sediment reworking (Irvine-Fynn et al., 2011). This accelerated geomorphic activity declines as soon as the metastable paraglacial system stabilizes caused by the exhaustion of paraglacial sediment storages or vegetation colonization (Ballantyne, 2002b). 1.2. Vegetation colonization and primary succession in glacier forefields Vegetation colonization starts with pioneer species. These are adapt- ed to the dominance of abiotic processes by their dispersal mechanisms (Chapin et al., 1994), their seed sizes and growth rates (Stöcklin and Bäumler, 1996), as well as by their physiognomy (Schröter et al., 1926). Colonization by pioneers proceeds to primary succession that can be defined as ‘species change on substrates with little or no biolog- ical legacy’ over time (Walker and del Moral, 2003, p. 7). This process is controlled by abiotic and biotic factors, which change with increas- ing terrain age, as described in the geoecological succession model (Matthews, 1992). At the beginning of primary succession, abiotic im- pacts are the most important influences (Raab et al., 2012). In glacier forefields, they include sediment characteristics and active geomor- phic processes (‘terrain age factor complex’) as well as topographic and hydrological controls such as snow melt, exposure, slope aspect, and moisture (‘microtopography factor complex’)(Matthews and Whittaker, 1987; Whittaker, 1987; Raffl et al., 2006). With proceed- ing vegetation succession, biotic processes – such as competition (Clements, 1928), facilitation, tolerance, and inhibition (Connell and Slatyer, 1977) – receive increasing importance (Matthews, 1992; Walker and del Moral, 2003; Raab et al., 2012). These temporal abiotic–biotic dynamics result in gradients in spe- cies composition, which can be interpreted as specific successional pathways, phases, and succession trends (Matthews, 1992). They in- clude increasing vegetation cover, biomass, and vegetation stratifica- tion with increasing terrain age (Walker and del Moral, 2003) and a Geomorphology xxx (2013) xxx–xxx ⁎ Corresponding author. Tel.: +49 228 739098; fax: +49 228 739099. E-mail address: j.eichel@uni-bonn.de (J. Eichel). GEOMOR-04394; No of Pages 13 0169-555X/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.geomorph.2013.06.012 Contents lists available at SciVerse ScienceDirect Geomorphology journal homepage: www.elsevier.com/locate/geomorph Please cite this article as: Eichel, J., et al., Biogeomorphic interactions in the Turtmann glacier forefield, Switzerland, Geomorphology (2013), http://dx.doi.org/10.1016/j.geomorph.2013.06.012