Glacier foreland succession and the fading effect of terrain age

Abstract

Questions What are the most important factors explaining present‐day variation in species composition in a glacier foreland? Does the rate of species compositional change in glacier forelands decelerate through primary succession? How do data set properties and analytic methods influence our understanding of glacier foreland successional dynamics? Location Nigardsbreen glacier foreland, western Norway. Methods We sampled the species composition and recorded 21 explanatory variables in 74 plots, distributed on eight classes of terrain age (dated moraines). Gradients in species composition found using global non‐metric multidimensional scaling (GNMDS) ordination were interpreted with split‐plot generalized linear models. Yearly succession rates were calculated from plot positions along a vector of maximum compositional change related to terrain age in the interpreted GNMDS ordination. Results We interpreted the main gradient in species composition as being related to a complex gradient with soil moisture and soil nutrients as primary constituents. Terrain age contributed to the second most important gradient. Succession rates were nonlinear with time. Terrain age explained variation in species composition only when plots from the two youngest terrain age classes were retained in the data set. Conclusions In contrast to the majority of studies of glacier foreland successions performed so far, we find that terrain age is not the principal factor that explains present‐day variation in species composition. Instead, local environmental variables are the main determinants of species composition. This result emphasizes the importance of taking environmental gradients into account when variation in glacier foreland vegetation is studied. The limited importance of terrain age in our study is interpreted as likely due to this glacier foreland being situated below the tree line, the relatively long distance between the bulk of the studied foreland and the glacier snout, and inclusion of few plots from young terrain in our data set. The non‐linearity of succession rates with time implies that a linear time‐since‐deglaciation variable is inappropriate for constrained ordination of glacier foreland vegetation.

Animal Successional Pathways for about 200 Years Near a Melting Glacier: A Norwegian Case Study

“…It has been argued for a 'geo-ecological' view on primary succession, where both biotic and abiotic factors were taken into considerations [4]. A recent study from Nigardsbreen foreland in Norway confirmed the modifying effect of microtopography on the floral succession [6].…”

“…• Are there alternative succession patterns for arthropods, in the same way as there are alternative succession patterns for vegetation [4][5][6]33]?…”

Impacts of Geomorphic Disturbances on Plant Colonization in Ebba Valley, Central Spitsbergen, Svalbard

“…Matthews (1978) and Whittaker (1989) emphasize that other variables than time and distance from the glacier may play the main role in creating vegetation spatial pattern. Also Rydgren et al (2014) proves that terrain age is not the main factor that explains present-day variation in species composition but local environmental variables may be more deterministic for vegetation structure. This also seems to be the case in Ebba Glacier foreland within all the zones.…”

“…Investigation of sample plots within homogenous sites (at the first sight) proves that calling into question the chronosequence approaches which "are based on the implicit assumption that spatial and temporal variations are equivalent" (Pickett 1989, Rydgren et al 2014:1367 is well justified. Matthews (1978) and Whittaker (1989) emphasize that other variables than time and distance from the glacier may play the main role in creating vegetation spatial pattern.…”

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“…Shrubs, but also clumps of certain herbaceous species, e.g., Saxifraga oppositifolia, have 84 a tendency to increase in size and number of flowering individuals with increasing terrain age 85 (Těšitel et al 2014). However, it has recently been shown that terrain age is not the principal 86 factor in explaining present-day variation in species composition in glacier forelands, and that 87 succession rates are not linearly related to time (Rydgren et al 2014 …”