Community assembly along proglacial chronosequences in the high Arctic: vegetation and soil development in north‐west Svalbard

Abstract

Summary 1 Community assembly is described for two contrasting high Arctic chronosequences representing glacial regression of up to 2000 years on Svalbard. The chronosequences included a nutrient-poor glacier foreland (Midtre Lovénbre) and a series of nutrientenriched islands (Lovén Islands) progressively released from below a tidewater glacier. 2 Soil development and community assembly paralleled proglacial sequences elsewhere but time scales were extended and mature vegetation types comprised species-poor prostrate communities. 3 Initial colonization by Cyanobacteria stabilized soil surfaces and raised nutrient status. Cyanobacteria formed the dominant ground cover (up to 34%) for 60 years, after when they declined. 4 Vascular plants established slowly and represented minor components of ground cover for the first 100 years. Earliest colonizers were often species with ectomycorrhizal associations , followed by mid-successional species that tended to disappear as ground cover increased. Some species present in the mature vegetation at the oldest sites, established only after 60+ years. 5 Species richness of vascular plants increased for c . 100 years, beyond when only occasional species were added. Bryophytes became increasingly dominant with time. 6 Soil development on the Midtre Lovénbre and Lovén Island chronosequences was similar after 100 years. Differences subsequently developed, with organic horizon depth, percentage organic matter and water content on the older Lovén islands significantly greater than at equivalent Midtre Lovénbre sites. This was associated with increased bryophyte cover but lower vascular plant species richness. One explanation is a slightly more favourable microclimate, coupled with nutrient input from nesting birds. 7 Communities progressively recruit from a limited pool of effectively dispersed species, each with particular ecological requirements that determine their point of entry into the community. A measure of determinism by default is suggested in the way communities assembled. 8 Under climate warming, in the absence of nutrient enrichment, community development will accelerate but will be constrained by nutrient limitations and a restricted species pool. Where nutrients are less limiting, acceleration towards a moss-dominated community is expected, with a lower species richness of vascular plants.

Vegetation diversity and selected abiotic factors influencing the primary succession process on the foreland of Gåsbreen, Svalbard

“…Since the 1980s, a number of studies has been conducted on glacier forelands on the north-western coast of Spitsbergen, near Ny-Ålesund (Brossard 1985;Moreau et al 2008). A significant proportion of the world's latest research related to primary succession on glacier marginal zones is based on this area and covers a variety of topics, including plant communities evolution (Hodkinson et al 2003;Moreau et al 2005;Moreau et al 2008), pioneering species , species ecology (Nakatsubo et al 2005;Uchida et al 2006;Yoshitake et al 2007), and the role of soil microorganisms (Bekku 2004), including mycorrhizal fungi . Apart from the Ny-Ålesund region, research has been conducted on the western coast of Spitsbergen (Tishkov 1986), in central Spitsbergen (Ziaja and Dubiel 1996;Prach and Rachlewicz 2012), and in southern Spitsbergen (Kuc 1964;Fabiszewski 1975;Pirożnikow and Górniak 1992;Wojtuń et al 2008).…”

“…In the case of bryophytes, only Kuc (1996) included specific names of species inhabiting glacier forelands. Regarding lichens, in studies conducted near Ny-Ålesund, only large fruticose terrestrial lichenised fungi, such as Cetrariella delisei, were taken into account (Hodkinson et al 2003;Moreau et al 2005), and from the total group of bryophytes only Sanionia uncinata and Polytrichaceae were noted (Moreau et al 2005). Only large terrestrial lichens (Cladonia mitis, Cetraria spp.…”

New Multicentury Evidence for Dispersal Limitation during Primary Succession

“…Soil C content increased with succession, typical for both forelands (Hodkinson et al 2003;Nakatsubo et al 2005;Tanner et al 2013) and circles (Walker et al 2008). The presence of soil C in young overburden might be attributable to preglacial organic matter that dominates soil C in soils !50 years old in an Austrian foreland (Bardgett et al 2007).…”

“…Here succession is characterized by shifts in dominant growth form, from cyanobacteria and bryophytes on recently exposed overburden, to deciduous vascular plants in intermediate seres, to evergreen plants in later seres (Chapin et al 1994;Hodkinson et al 2003;Jones and Henry 2003;Nakatsubo et al 2005;Robbins and Matthews 2009). High latitudes are expected to be especially prone to anthropogenic climate warming, accelerating glacial melt and the exposure of forelands (Heckmann et al 2015).…”

“…In glacial forelands, the chronosequence spans some kilometers (Hodkinson et al 2003;Nakatsubo et al 2005;Robbins and Matthews 2009), but in sorted circles, the successional chronosequence spans several meters (Kessler and Werner 2003;Haugland and Beatty 2005;Walker et al 2008). Thus, propagules need to disperse several kilometers on forelands but only a few meters on circles.…”