Impact of climate change on alpine vegetation of mountain summits in Norway

Thomas Vanneste,Sigrid Lindmo,Magni Olsen Kyrkjeeide,Rozália Erzsebet Kapás,Pieter De Frenne,Håkon Holien,Kristian Hassel,Bente Jessen Graae,Ottar Michelsen

doi:10.1007/s11284-017-1472-1

Abstract

Climate change is affecting the composition and functioning of ecosystems across the globe. Mountain ecosystems are particularly sensitive to climate warming since their biota is generally limited by low temperatures. Cryptogams such as lichens and bryophytes are important for the biodiversity and functioning of these ecosystems, but have not often been incorporated in vegetation resurvey studies. Hence, we lack a good understanding of how vascular plants, lichens and bryophytes respond interactively to climate warming in alpine communities. Here we quantified long-term changes in species richness, cover, composition and thermophilization (i.e. the increasing dominance of warm-adapted species) of vascular plants, lichens and bryophytes on four summits at Dovrefjell, Norway. These summits are situated along an elevational gradient from the low alpine to high alpine zone and were surveyed for all species in 2001, 2008 and 2015. During the 15-year period, a decline in lichen richness and increase in bryophyte richness was detected, whereas no change in vascular plant richness was found. Dwarf-shrub abundance progressively increased at the expense of lichens, and thermophilization was most pronounced for vascular plants, but occurred only on the lowest summits and northern aspects. Lichens showed less thermophilization and, for the bryophytes, no significant thermophilization was found. Although recent climate change may have primarily caused the observed changes in vegetation, combined effects with non-climatic factors (e.g. grazing and trampling) are likely important as well. At a larger scale, alpine vegetation shifts could have a profound impact on biosphere functioning with feedbacks to the global climate.

Highlights

Biological consequences of climate change are increasingly evident across a wide range of ecosystems
Dwarf-shrub abundance progressively increased at the expense of lichens, and thermophilization was most pronounced for vascular plants, but occurred only on the lowest summits and northern aspects
We observed a significant increase in the cover of some vascular plant species at a relatively constant rate between 2001 and 2015, especially for dwarf shrubs (B. nana, E. nigrum, V. uliginosum and V. vitis-idaea) and graminoids (F. ovina, J. trifidus and L. arcuata), but almost exclusively on the lowest summit

Summary

Introduction

Biological consequences of climate change are increasingly evident across a wide range of ecosystems. Tundra ecosystems are considered to be susceptible to global warming as they are generally limited by low temperatures (Klanderud and Birks 2003; Walker et al 2006; Elmendorf et al 2015). These ecosystems can be used as indicators for the impacts of climate change (Grabherr et al 2010; Malanson et al 2011), and they provide an excellent base for detection of its early-warning signals (Wolf et al 2012). Widespread implications of warming on tundra vegetation have been reported (Post et al 2009; Mayor et al 2017), including an upslope migration and increasing species richness of vascular plants (Pauli et al 2007) and a progressive shrub expansion (Myers-Smith et al 2011)

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Discussion

Conclusion