View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by ZHAW digitalcollection J Insect Conserv (2012) 16:657–675 DOI 10.1007/s10841-011-9448-x ORIGINAL PAPER Environmental gradients and succession patterns of carabid beetles (Coleoptera: Carabidae) in an Alpine glacier retreat zone Ju¨rg Schlegel • Matthias Riesen Received: 28 June 2011 / Accepted: 10 November 2011 / Published online: 30 November 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Accelerated by global warming, retreating Habitat loss as a result of climate warming will primarily glaciers leave behind spatially ordered moraines with affect cold-stenotopic carabids, but may potentially be underlying primary succession and disturbance. Current absorbed by active selection for cooler microhabitats. knowledge of primary succession comes mainly from studies of vegetation dynamics. Information about above- Keywords Glacier foreland Á Invertebrate fauna Á ground macroinvertebrates is still scarce. We used carabid Primary succession Á Habitat factors Á Climate change Á beetles (Coleoptera; Carabidae) as indicator taxon to assess Swiss Alps the effects of (1) terrain age (species turnover along the proglacial chronosequence) and (2) small-scale habitat architecture (vegetation cover, surface texture) on the Introduction carabid assembly. For this purpose, 33 sampling sites with pitfall traps were installed throughout the glacier foreland Retreating glaciers are considered to be key indicators of Morteratsch (Engadine, Switzerland), adjacent sparse for- global warming (IPCC 2007; Oerlemans 2005; Paul et al. ests serving as reference sites. With a total of 33 carabid 2004). It is estimated that glaciers in the European Alps species on the foreland and another 2 on the reference sites, lost about half of their total volume between around 1850 the study area yielded a very high carabid species diversity (‘‘little ice age’’) and 1975, another 25% of the remaining compared to other glacier forelands. In general, the age of amount between 1975 and 2000, and an additional 10–15% deglaciation proved to be a highly significant predictor for in the first 5 years of this century (Haeberli et al. 2007). the carabid distribution, especially for particularly dis- Based on extrapolations of the ‘‘Swiss Glacier Inventory criminant species. Observed species richness and activity 2000’’, a total of more than 600 km2 has become ice-free densities showed bimodal patterns with a steep increase since 1850 (Zemp et al. 2007). within the first ca. 40 years, a decline between around Retreating glaciers leave behind barren moraines with 40–90 years, and a further increase towards the terminal various textures, stability and fertility, consisting of fine moraine. There was no evidence of dispersal-stochasticity: rock flour particles up to larger boulders. Secondary dis- distinct clusters of sites with similar species composition turbances following deglaciation include landslides from were found. Microhabitat suitability proved to be a sec- the side moraines, floodplains, wind-blown loess and winds ondary effect, embedded in a temporal framework of pri- that desiccate and cool the environment (Walker and Del mary succession. Surface cover with litter, herbs and Moral 2003). Dynamic processes such as transportation or dwarf-shrubs turned out to be the crucial habitat factors. rearrangement of till in front of the glacier snout form an unstable habitat (Geo7 and UNA 1998). Primary succession is ecosystem development in situa- J. Schlegel (&) Á M. Riesen tions where no previously developed soil exists (Dobson Institute of Natural Resource Sciences, ZHAW Zurich et al. 1997). Glacier forelands represent ideal spatio-tem- University of Applied Sciences, Gru¨ental, 8820 Wa¨denswil, Switzerland poral model systems for studying primary succession and e-mail: [email protected] recovery from severe disturbance. As most of our 123 658 J Insect Conserv (2012) 16:657–675 knowledge of primary succession comes from descriptive studies on glacier forelands in Scandinavia, while Hod- studies of vegetation development (Wood and Del Moral kinson et al. (2004) examined higher latitudes in Spits- 1987), information about fauna is scarce and often anec- bergen. Scattered information about particular alpine dotal (Mrzljak and Wiegleb 2000). invertebrate species is found in many checklists, studies Common understanding of succession implicates pho- and surveys (e.g. Killias 1894 for the beetle fauna in the toautotrophic plants as the first colonisers of newly gen- Upper Engadine), but it generally does not allow conclu- erated substrates. In primary succession, however, a review sions to be drawn about small-scale habitat colonisation on by Hodkinson et al. (2002) amassed many research projects glacier forelands. with heterotrophic organisms as leadoff arrivals. This also Due to effective passive and active dispersal mecha- seems to hold true for newly exposed glacier moraines nisms and high reproductive rates, many invertebrates react where predators were almost exclusively the first colonis- more quickly to environmental conditions than plant ers, as observed in the Arctic (Hodkinson et al. 2001) and communities: this also seems to be true in the Alpine zone, in central Europe (Kaufmann 2001). The typical sequence where all processes slow down with increasing altitude in secondary succession, where invertebrate carnivores (Kaufmann 2004). At the opposite extreme, microorgan- follow herbivorous invertebrates (Kaufmann 2001), is isms, with their very rapid responses to changing envi- reversed. The diet of the first arrivals, among those pred- ronmental conditions, tend to fluctuate more wildly and be atory carabids, is organic ‘‘fallout’’ such as springtails and less stable indicators of longer-term trends (Hodkinson and aphids, drifted by wind turbulence. Walker and Del Moral Jackson 2005). Invertebrates, for example the surface (2003) mention insects on barren sites hastening soil active carabid beetles (=ground beetles; Coleoptera, Cara- development by introducing carbon and nitrogen. bidae), are therefore considered to have high overall Soil and vegetation development on glacier forelands in potential to serve as good indicators when studying land- the European Alps are well documented (e.g. Caccianiga scape features and habitat changes (New 2010, but see and Andreis 2004 in the Italian Alps; Burga 1999, Egli reservations in Rainio and Niemela¨ 2003). Literature et al. 2006 in the Swiss Alps; Raffl et al. 2006 in the focusing on the response of carabid beetles to changing Austrian Alps). Research on soil communities has been environments is diverse (Gobbi et al. 2007), especially for conducted by Matthews (1992), Ohtonen et al. (1999), lowland agroecosystems (e.g. Aviron et al. 2005) and for- Tscherko et al. (2005) and numerous others. Several studies ests (e.g. Fuller et al. 2008). Although carabids found in have analysed the succession of microbes on glacier fore- European mountains have been studied by several authors lands (e.g. Sigler et al. 2002). Ha˚gvar (2010) analysed the (see review in Brandmayr et al. 2003), little is known about springtail fauna, and Seniczak et al. (2006) determined the responses of carabids to climate and ecosystem chan- oribatid mites in Norwegian glacier forelands. Recent ges. Carabids are diverse and abundant, occur in all major research in proglacial areas highlights the potential of terrestrial habitats, and are generally well documented invertebrate fauna to help understand the responses of taxonomically and autecologically (Lindroth 1986; Marggi living organisms to environmental and climatic changes 1992). They are mainly epigaeic, which allows for easy (Gobbi et al. 2006b; Kaufmann 2001). Albrecht et al. collection with pitfall traps (Thiele 1977; Samways et al. (2010) studied interactions between insect-pollinated plants 2010) and makes large samples of individuals often easy to and plant-pollinating insects. The zoobenthos of glacier-fed obtain. Many studies have proved significant correlations streams has been documented in several studies, e.g. by to habitat characteristics and habitat modifications (New Milner et al. (2002) and Robinson et al. (2001). 2010). Despite all the research projects mentioned and the need Spatially ordered chronosequences of increasing age to enhance biological knowledge, very few studies have might represent, with some care, the history of succession focussed on the primary succession of above-ground in glacier forelands (Matthews 1992; Kaufmann 2001). macroinvertebrates on glacier forelands. Matthews (1992) Walker and Del Moral (2003) presume a nonlinear process noted the absence of relevant published data in respect of of change in proglacial areas. Burga et al. (2010) also animals in glacier forelands at the time of his study. In found non-linear microhabitat-controlled (grain size, water Europe, research on epigaeic arthropods is primarily supply, microclimate) succession patterns with different restricted to studies by Janetschek (1949, 1958), Franz pathways for the different ecological niches on the Mort- (1969), Gereben (1995), Paulus and Paulus (1997), Kauf- eratsch glacier foreland, converging to a common ‘‘cli- mann (2001, 2002, 2004), and Kaufmann and Raffl (2002) max’’. Time since deglaciation did not sufficiently in the Austrian Alps. Gobbi et al. (2006a, b, 2007, 2010, contribute to a better understanding of small-scale plant 2011) studied ground-dwelling arthropods on glacier succession. forelands