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Keywords:

  • Alpine tundra;
  • Cryoturbation;
  • Deflation;
  • Fluvial processes;
  • Geomorphology;
  • Nivation;
  • Solifluction;
  • Species distribution modelling

Abstract

Questions

Are earth surface processes (ESPs) important determinants of species richness, composition and fine-scale distributions? Do different ESPs have similar effects on these vegetation characteristics?

Location

Saana massif, northwest Finland (69 °N).

Methods

Vascular plant species occurrences, five environmental variables (related to soil conditions and topography) and five ESPs were surveyed across 960 1-m2 quadrats in arctic–alpine tundra. Community composition was examined using non-metric multi-dimensional scaling (NMDS), while species richness and individual species occurrence were modelled using GLMs, GAMs and boosted regression trees.

Results

Three ESPs (solifluction, fluvial activity and nivation) were strongly related to community composition, with only soil moisture and mesotopography exhibiting stronger correlations with NMDS scores. ESPs significantly improved the accuracy of species richness models based on soil conditions and topography, with solifluction and fluvial processes having the largest individual contributions. Solifluction and fluvial activity also increased the predictive power of species distribution models, with these processes often being as influential on occurrence patterns as some of the traditionally utilized direct and resource variables. Arctic–alpine species generally responded positively to ESPs, with boreal species showing the opposite trend.

Conclusions

This study, the first to examine the impacts of several independent ESPs on multiple vegetation characteristics, demonstrates that ESPs are primary drivers of species fine-scale distributions, species richness and community composition in arctic–alpine plant communities. ESPs varied in their effect and relative influence, and thus several ESPs need to be considered when examining species- and community-level properties of vegetation.