The response of plant diversity to grazing varies along an elevational gradient

Speed, James D. M.; Austrheim, Gunnar; Mysterud, Atle

doi:10.1111/1365-2745.12133

Cited by 48 publications

(52 citation statements)

References 57 publications

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“…Grazing by sheep and reindeer is increasing throughout Norway and the number of herbivores increased by approximately 6% in Dovrefjell during the last decades (Syverhuset 2009). Grazing has the potential to buffer climate-induced changes in plant diversity as it can hamper the increase in species richness and abundance at high elevations (Pajunen et al 2012;Speed et al 2013;Barrio et al 2016). The absence of an increasing trend in vascular plant species richness on our study summits could, therefore, also be related to the increasing number of grazing mammals.…”

Section: Other Possible Drivers Of Changes In Vegetationmentioning

confidence: 99%

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

Vanneste

Michelsen

Graae

et al. 2017

Ecological Research

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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.Keywords Alpine vegetation AE Climate change AE Resurvey study AE Thermophilization AE CryptogamsThe original version of this article was revised due to a retrospective Open Access.Electronic supplementary material The online version of this article

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Section: Other Possible Drivers Of Changes In Vegetationmentioning

confidence: 99%

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

Vanneste

Michelsen

Graae

et al. 2017

Ecological Research

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“…At this stage the impact on ecosystem C stocks will be minor. (2) On a longer timescale (decades) shifts in vegetation composition (Speed et al, 2013) may occur, and increased tree recruitment and growth above the treeline may become apparent (Speed et al, 2011b). Any vegetation changes are likely to lead to changes in litter quality, increasing the decomposability of soil organic matter (Kammer et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

Continuous and discontinuous variation in ecosystem carbon stocks with elevation across a treeline ecotone

et al. 2015

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Abstract. Treelines differentiate vastly contrasting ecosystems: open tundra from closed forest. Treeline advance has implications for the climate system due to the impact of the transition from tundra to forest ecosystem on carbon (C) storage and albedo. Treeline advance has been seen to increase above-ground C stocks as low vegetation is replaced with trees but decrease organic soil C stocks as old carbon is decomposed. However, studies comparing across the treeline typically do not account for elevational variation within the ecotone. Here we sample ecosystem C stocks along an elevational gradient (970 to 1300 m), incorporating a large-scale and long-term livestock grazing experiment, in the southern Norwegian mountains. We investigate whether there are continuous or discontinuous changes in C storage across the treeline ecotone, and whether these are modulated by grazing. We find that vegetation C stock decreases with elevation, with a clear breakpoint between the forest line and treeline above which the vegetation C stock is constant. C stocks in organic surface horizons of the soil were higher above the treeline than in the forest, whereas C stocks in mineral soil horizons are unrelated to elevation. Total ecosystem C stocks also showed a discontinuous elevational pattern, increasing with elevation above the treeline (8 g m −2 per metre increase in elevation), but decreasing with elevation below the forest line (−15 g m −2 per metre increase in elevation), such that ecosystem C storage reaches a minimum between the forest line and treeline. We did not find any effect of short-term (12 years) grazing on the elevational patterns. Our findings demonstrate that patterns of C storage across the treeline are complex, and should be taken account of when estimating ecosystem C storage with shifting treelines.

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“…; Olofsson ; van der Wal & Hessen ). Moreover, some studies also highlight that the effects of grazing on tundra plant communities cannot be considered in isolation from several locally varying factors such as soil nutrient status (Eskelinen, Harrison & Tuomi ) and many abiotic conditions changing with an elevation gradient (Speed, Austrheim & Mysterud ).…”

Section: Introductionmentioning

confidence: 99%

Environmental perturbation, grazing pressure and soil wetness jointly drive mountain tundra toward divergent alternative states

et al. 2014

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Summary1. Plant communities are structured by complex interactions between multiple factors, which veil our understanding of the effects of environmental changes on communities and ecosystems. Besides the relative role of biotic and abiotic factors as community-structuring processes, addressing how they jointly affect the ecological resilience and resistance of plant communities is crucial to understand better the long-term response of communities facing global changes. 2. Here, we used the results from a long-term (23 years) perturbation experiment set up in Fennoscandian mountain tundra to test these mechanisms. The experiment consisted of a transplantation of twenty blocks of Vaccinium myrtillus heath vegetation including upper soil layer from a lower elevation tundra heath habitat to a snowbed habitat 150 m higher in elevation where V. myrtillus lies at its upper limit. In the snowbed with contrasting levels of soil wetness, half of the transplanted blocks were protected from mammalian herbivores. 3. Our results revealed that in addition to the important role of environmental conditions as a structuring force, the joint effects of multiple drivers resulted in divergent patterns in both plant functional composition and species diversity among transplanted communities. Under environmental perturbation (i.e. transplantation to snowbed), the heath vegetation was altered by grazing pressure that reduced the cover of shrubs (especially V. myrtillus). In grazed dry snowbed, a species-rich community with high functional type evenness and diversity developed. Reversely, in dry exclosures, V. myrtillus gained high dominance associated with only few graminoids and forbs. In wet snowbed conditions, shrubs tended to decline both in grazed plots and exclosures whereas bryophytes attained high abundance. Grazing promoted species richness while soil waterlogging tended to promote among-plot heterogeneity (b-diversity) which was highest in wet exclosures. 4. Synthesis. Our long-term experiment reveals that environmental perturbation, grazing and soil wetness exhibit joint effects that induce divergent trajectories of tundra plant communities. We suggest that a strong environmental perturbation triggers mountain tundra heath community to move away from its equilibrium state. The outcome of this shift depends on the interplay between grazing pressure and soil wetness that drive tundra plant communities toward divergent alternative states.

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The response of plant diversity to grazing varies along an elevational gradient

Cited by 48 publications

References 57 publications

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

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

Continuous and discontinuous variation in ecosystem carbon stocks with elevation across a treeline ecotone

Environmental perturbation, grazing pressure and soil wetness jointly drive mountain tundra toward divergent alternative states

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