Abstract

Climate change is expected to affect alpine and Arctic tundra communities. Most previous long-term studies have focused on impacts on vascular plants, this study examined impacts of long-term warming on bryophyte communities. Experimental warming with open-top chambers (OTCs) was applied for 18 years to a mesic meadow and a dry heath alpine plant community. Species abundance was measured in 1995, 1999, 2001 and 2013. Species composition changed significantly from original communities in the heath, but remained similar in mesic meadow. Experimental warming increased beta diversity in the heath. Bryophyte cover and species richness both declined with long-term warming, while Simpson diversity showed no significant responses. Over the 18-year period, bryophyte cover in warmed plots decreased from 43 % to 11 % in heath and from 68 % to 35 % in meadow (75 % and 48 % decline, respectively, in original cover), while richness declined by 39 % and 26 %, respectively. Importantly, the decline in cover and richness first emerged after 7 years. Warming caused significant increase in litter in both plant communities. Deciduous shrub and litter cover had negative impact on bryophyte cover. We show that bryophyte species do not respond similarly to climate change. Total bryophyte cover declined in both heath and mesic meadow under experimental long-term warming (by 1.5–3 °C), driven by general declines in many species. Principal response curve, cover and richness results suggested that bryophytes in alpine heath are more susceptible to warming than in meadow, supporting the suggestion that bryophytes may be less resistant in drier environments than in wetter habitats. Species loss was slower than the decline in bryophyte abundance, and diversity remained similar in both communities. Increased deciduous shrub and litter cover led to decline in bryophyte cover. The non-linear response to warming over time underlines the importance of long-term experiments and monitoring.

Highlights

  • Arctic and alpine ecosystems are likely to experience a faster rate of warming than the global average (Chapin et al 1995; Mack et al 2004; IPCC 2013)

  • The principal response curves (PRCs) for the meadow, with 1995 used as reference, indicated that the species composition of the warming and control plots was relatively different at the start of the experiment, but between 2001 and 2013 it became more similar (Fig. 1)

  • Most previous studies on the potential impact of climate change on bryophytes have focused on cover/biomass (Sistla et al 2013), but this study we examined the potential impact of warming on bryophyte community composition

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Summary

Introduction

Arctic and alpine ecosystems are likely to experience a faster rate of warming than the global average (Chapin et al 1995; Mack et al 2004; IPCC 2013). Bryophytes are important contributors to ecosystem services, while some host nitrogen-fixing bacteria and provide nitrogen inputs to ecosystems (During and Van Tooren 1990; Turetsky 2003). They act as the major food source for some invertebrates (Collembola, cranefly, various species of Diptera) and vertebrates (Soay sheep, reindeer, barnacle geese) (Herbert and Prins 1982; Crafford and Chown 1991; Hodkinson et al 1994; Smith et al 2001; Glime 2006; Imada and Kato 2016). Vascular plants rather than bryophytes have been the focus of most climate change studies to date (Arft et al 1999; Walker et al 2006; Elmendorf et al 2012a; 2012b; Alatalo et al 2014b; Dumais et al 2014; Wheeler et al 2016; Zhang et al 2016)

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