Complex effects of mammalian grazing on extramatrical mycelial biomass in the Scandes forest‐tundra ecotone

Vowles, Tage; Lindwall, Frida; Ekblad, Alf; Bahram, Mohammad; Furneaux, Brendan; Ryberg, Martin; Björk, Robert G.

doi:10.1002/ece3.3657

Cited by 13 publications

(11 citation statements)

References 76 publications

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“…In line with our first hypothesis and some earlier studies linking reindeer grazing to altered fungal community composition and growth (Santalahti et al, 2018; Vowles et al, 2018), we found that root‐associated ascomycetes, including ErM fungi, were most abundant away from mountain birches in the grazing regime exposed to year‐round reindeer grazing and tightly linked to the abundance of ericaceous dwarf shrubs. In contrast, the abundance of root‐associated basidiomycetes, mostly forming EcM, was linked to the relative abundance of Betula DNA in the soil.…”

Section: Discussionsupporting

confidence: 92%

Reindeer control over subarctic treeline alters soil fungal communities with potential consequences for soil carbon storage

Ylänne

Madsen

Castaño

et al. 2021

Global Change Biology

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The climate‐driven encroachment of shrubs into the Arctic is accompanied by shifts in soil fungal communities that could contribute to a net release of carbon from tundra soils. At the same time, arctic grazers are known to prevent the establishment of deciduous shrubs and, under certain conditions, promote the dominance of evergreen shrubs. As these different vegetation types associate with contrasting fungal communities, the belowground consequences of climate change could vary among grazing regimes. Yet, at present, the impact of grazing on soil fungal communities and their links to soil carbon have remained speculative. Here we tested how soil fungal community composition, diversity and function depend on tree vicinity and long‐term reindeer grazing regime and assessed how the fungal communities relate to organic soil carbon stocks in an alpine treeline ecotone in Northern Scandinavia. We determined soil carbon stocks and characterized soil fungal communities directly underneath and >3 m away from mountain birches (Betula pubescens ssp. czerepanovii) in two adjacent 55‐year‐old grazing regimes with or without summer grazing by reindeer (Rangifer tarandus). We show that the area exposed to year‐round grazing dominated by evergreen dwarf shrubs had higher soil C:N ratio, higher fungal abundance and lower fungal diversity compared with the area with only winter grazing and higher abundance of mountain birch. Although soil carbon stocks did not differ between the grazing regimes, stocks were positively associated with root‐associated ascomycetes, typical to the year‐round grazing regime, and negatively associated with free‐living saprotrophs, typical to the winter grazing regime. These findings suggest that when grazers promote dominance of evergreen dwarf shrubs, they induce shifts in soil fungal communities that increase soil carbon sequestration in the long term. Thus, to predict climate‐driven changes in soil carbon, grazer‐induced shifts in vegetation and soil fungal communities need to be accounted for.

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Section: Discussionsupporting

confidence: 92%

Reindeer control over subarctic treeline alters soil fungal communities with potential consequences for soil carbon storage

Ylänne

Madsen

Castaño

et al. 2021

Global Change Biology

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“…Throughout the Arctic, large herbivores are well known to influence plant community structure [15][16][17], and ecosystem processes and functions [18][19][20][21]. It is, however, difficult to quantify the magnitude of these effects.…”

Section: Effects Of Large Herbivores On Tundra Vegetationmentioning

confidence: 99%

“…The densities of large herbivores inhabiting the mammoth steppe in Alaska and northeastern Siberia have been estimated to have been as high as 105 kg ha 21, [68], which is more than an order of magnitude greater than present herbivore densities. For a comparison, domesticated reindeer in Scandinavia today rarely exceed 3 kg ha 21 . Zimov et al [7,67] proposed that this high density of herbivores resulted in the graminoid dominance of the mammoth steppe, which in turn contributed to a high nutrient availability both by providing high quality litter that decomposed quickly and by maintaining a high rate of transpiration which resulted in dry oxygenated soils, further contributing to a high nutrient mineralization rate and nutrient availability.…”

Section: The Mammoth Steppementioning

confidence: 99%

Effects of large herbivores on tundra vegetation in a changing climate, and implications for rewilding

Olofsson

Post

2018

Phil. Trans. R. Soc. B

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In contrast to that of the Pleistocene epoch, between approximately 2.6 million and 10 000 years before present, the extant community of large herbivores in Arctic tundra is species-poor predominantly due to human extinctions. We here discuss how this species-poor herbivore guild influences tundra ecosystems, especially in relation to the rapidly changing climate. We show that present herbivore assemblages have large effects on tundra ecosystem composition and function and suggest that the effect on thermophilic species expected to invade the tundra in a warmer climate is especially strong, and that herbivores slow ecosystem responses to climate change. We focus on the ability of herbivores to drive transitions between different vegetation states. One such transition is between tundra and forest. A second vegetation transition discussed is between grasslands and moss- and shrub-dominated tundra. Contemporary studies show that herbivores can drive such state shifts and that a more diverse herbivore assemblage would have even higher potential to do so. We conclude that even though many large herbivores, and especially the megaherbivores, are extinct, there is a potential to reintroduce large herbivores in many arctic locations, and that doing so would potentially reduce some of the unwanted effects of a warmer climate. This article is part of the theme issue ‘Trophic rewilding: consequences for ecosystems under global change’.

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“…Côté, Rooney, Tremblay, Dussault, & Walker, ; Estes et al, ; Jia et al, ; Tanentzap & Coomes, ). In the high‐latitude ecosystems of Eurasia and North America, reindeer and caribou ( Rangifer tarandus L.) are well known to influence plant community structure (Bernes, Bråthen, Forbes, Speed, & Moen, ; Jefferies, Klein, & Shaver, ; Suominen & Olofsson, ), and ecosystem processes and functions (Christie et al, ; Väisänen et al, ; Vowles et al, ), particularly at the local scale. Hence, a recent systematic review of the current literature on reindeer effects on vegetation patterns across high‐latitude ecosystems found strong local responses to reindeer grazing in a wide array of plant functional groups (Bernes et al, ).…”

Section: Introductionmentioning

confidence: 99%

Experimental evidence of the long‐term effects of reindeer on Arctic vegetation greenness and species richness at a larger landscape scale

et al. 2019

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1. Large herbivores influence plant community structure and ecosystem processes in many ecosystems. In large parts of the Arctic, reindeer (or caribou) are the only large herbivores present. Recent studies show that reindeer have the potential to mitigate recent warming-induced shrub encroachment in the Arctic and the associated greening of high-latitude ecosystems. This will potentially have large scale consequences for ecosystem productivity and carbon cycling.2. To date, information on variation in the interactions between reindeer and plants across Arctic landscapes has been scarce. We utilized a network of experimental sites across a latitudinal gradient in the Scandinavian mountains where reindeer have been excluded from 59 study plots for at least 15 years. We used this study system to test the effect of long-term exclusion of reindeer on the abundance of major plant functional groups, the greenness indexes Leaf Area Index (LAI) andNormalized Difference Vegetation Index (NDVI), soil mineral nitrogen (N) and phosphorous (P), and species richness, and to determine whether the effect of reindeer exclusion is dependent on reindeer density, productivity, soil fertility or climate.3. We found that NDVI and LAI, lichen and deciduous shrub abundances were largely reduced while soil mineral N was enhanced by reindeer. The direction and amplitude of other plant functional group responses to reindeer exclusion differed between forest and tundra as well as shrub-and herbaceous-dominated vegetation. Higher reindeer densities were related to decreased plant species richness in low-productive sites and to increased species richness in productive sites. The relative reduction in LAI and associated absolute reductions of deciduousshrubs in response to reindeer were positively related to reindeer density, while the relative reduction in NDVI was not. Further, relative reductions in LAI and NDVI in response to reindeer were unrelated to climate and soil fertility. Synthesis.Our results provide long-term experimental evidence highlighting the role of reindeer density in regulating plant species richness, global climate change induced greenness patterns and shrub encroachment at regional scales in the Arctic. These findings emphasize the need to consider reindeer in models predicting vegetation patterns and changes in high-latitude ecosystems. | 2725Journal of Ecology SUNDQVIST eT al.

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Complex effects of mammalian grazing on extramatrical mycelial biomass in the Scandes forest‐tundra ecotone

Cited by 13 publications

References 76 publications

Reindeer control over subarctic treeline alters soil fungal communities with potential consequences for soil carbon storage

Reindeer control over subarctic treeline alters soil fungal communities with potential consequences for soil carbon storage

Effects of large herbivores on tundra vegetation in a changing climate, and implications for rewilding

Experimental evidence of the long‐term effects of reindeer on Arctic vegetation greenness and species richness at a larger landscape scale

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