Reindeer influence on ecosystem processes in the tundra

Olofsson, Johan; Stark, Sari; Oksanen, Lauri

doi:10.1111/j.0030-1299.2004.13048.x

Cited by 196 publications

(259 citation statements)

References 50 publications

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“…My results indicate that the reindeer-induced transition from dwarf shrub-to graminoid-dominated ecosystems (Olofsson et al , 2004) is reversible, but that the recovery of dwarf shrubs is a slower process than the increase of graminoids. This is in agreement with studies from boreal ecosystems, where dwarf-shrubs replace graminoids after only a few years of fertilization (Strengbom et al 2002), whereas it takes decades for the dwarf shrubs to recover after fertilization has ended (Strengbom et al 2001).…”

Section: Discussionmentioning

confidence: 83%

“…4). Long-term intensive grazing has transformed the dwarf-shrub and moss-dominated heathlands into grass and sedge meadows with higher soil temperatures, higher nutrient turnover and higher primary production (Olofsson et al , 2004.…”

Section: Discussionmentioning

confidence: 99%

“…However, the graminoid-dwarf shrub transition is not a gradual cline, but is represented as a sharp boundary at the fence Olofsson et al 2004). Thus, it is highly unlikely that the vegetation transition is caused by an environmental gradient other than grazing, especially as it occurs across the boundary of different fences .…”

Section: Discussionmentioning

confidence: 99%

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Short‐ and long‐term effects of changes in reindeer grazing pressure on tundra heath vegetation

2006

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Summary1 Previous studies of plant-herbivore interactions have typically focused either on short-term or long-term effects. By directly comparing effects at different temporal scales, I studied whether short-term experiments provide good indications of the long-term effects of herbivory. 2 I reciprocally transplanted turfs of tundra heath vegetation within areas covered by a long-term (40 years) reindeer manipulation experiment, in order to examine the effects of all possible permutations of light, moderate and heavy grazing pre-and post-transplantation. 3 The effects of a short-term (three growing seasons) increase in reindeer grazing pressure gave good qualitative indications of most of the long-term effects of grazing on plant biomass, species richness, moss cover and lichen cover. In contrast, reducing grazing pressure on previously heavily grazed vegetation had no significant effects on any of these variables over the same time-scale. 4 Although few effects on individual species were recorded from the short-term manipulations, all those that were significant were qualitatively similar to the long-term responses of the respective species to herbivory. 5 The grass-dominated vegetation from the heavily grazed area changed little when grazing and trampling pressure were reduced for 3 years. In contrast, the dwarf shrubdominated vegetation in the lightly grazed area changed rapidly into grasslands when the grazing pressure was enhanced. 6 Re-establishment of dwarf shrubs appears to be both seed and microsite limited, but it appears that dwarf shrubs may be able to re-establish in previously heavily grazed vegetation in the absence of reindeer. 7 Transitions from moss-or dwarf shrub-dominated ecosystems to grass-dominated ecosystems are currently occurring at different locations in boreal, arctic and alpine regions due to atmospheric nitrogen deposition and livestock grazing. This loss of habitat may be reversible, given a relatively long time frame.

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Section: Discussionmentioning

confidence: 83%

Section: Discussionmentioning

confidence: 99%

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Short‐ and long‐term effects of changes in reindeer grazing pressure on tundra heath vegetation

2006

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“…With fewer megafauna on the landscape and proboscideans absent, the reduction of trampling, browsing, and grazing pressure by big animals is postulated to have stimulated an increase in woody and leafy plants, which set off an ecological cascade by promoting accumulation of surface leaf litter that insulated soil, reduced summer soil temperatures, caused formation of permafrost, and favored growth of mosses and shrubs at the expense of grasses and other nutritious fodder for herbivores. Experimental studies support this idea (26,27,65).…”

Section: Significancementioning

confidence: 91%

Variable impact of late-Quaternary megafaunal extinction in causing ecological state shifts in North and South America

Barnosky

Lindsey

Villavicencio

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

116

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Loss of megafauna, an aspect of defaunation, can precipitate many ecological changes over short time scales. We examine whether megafauna loss can also explain features of lasting ecological state shifts that occurred as the Pleistocene gave way to the Holocene. We compare ecological impacts of late-Quaternary megafauna extinction in five American regions: southwestern Patagonia, the Pampas, northeastern United States, northwestern United States, and Beringia. We find that major ecological state shifts were consistent with expectations of defaunation in North American sites but not in South American ones. The differential responses highlight two factors necessary for defaunation to trigger lasting ecological state shifts discernable in the fossil record: (i) lost megafauna need to have been effective ecosystem engineers, like proboscideans; and (ii) historical contingencies must have provided the ecosystem with plant species likely to respond to megafaunal loss. These findings help in identifying modern ecosystems that are most at risk for disappearing should current pressures on the ecosystems' large animals continue and highlight the critical role of both individual species ecologies and ecosystem context in predicting the lasting impacts of defaunation currently underway. megafauna | extinction | Quaternary | North America | South America D efaunation is occurring at a rapid pace presently (1-3).Losses are particularly severe for megafauna (1) (considered here as animals with an average body size ≥44 kg), whose removal can trigger the following: changes in vegetation structure and species composition; reductions in environmental heterogeneity, species richness, evenness, seed dispersal, nutrient cycling and distribution, and ecosystem services; coextinction of dependent species; and increases in disease-transmitting organisms (1, 4-14) and fire frequency and/or intensity (15-17).Most work on defaunation has been in contemporary ecosystems. Much less is known about how it manifests over millennial time scales. A natural experiment to assess lasting effects of megafauna loss is provided by the extinctions of late-Quaternary megafauna in the Americas, part of global-scale ecological state shift (18), during which about half of the world's large-bodied mammal species (19,20) disappeared. In North America, ∼60 megafaunal species died out, with the youngest occurrences of dated species typically falling between ∼13,000 and 11,000 y ago (19). In South America, ∼66 species were lost over a longer time span (21-23).With a few important exceptions (6, 17, 24-29), the major changes in vegetation and mammalian community structure that accompanied Quaternary extinctions have been interpreted as responses to changing climate (17-19, 21, 23, 25-27, 29-35). Here, we build on recent work of paleoecologists (17,25,28,29,32,36) and ecologists (1, 3-7, 9, 10, 15, 16, 37) ApproachThe late-Quaternary impact of losing 70-80% of the megafauna genera in the Americas (19) would be expected to trigger biotic transitions that would b...

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“…This is undoubtedly the case for large herbivores, although lemmings and voles will not be excluded from OTCs, and reduced pollination has not been identified as a problem to date. The exclusion of large herbivores from OTC plots and not from control plots is an experimental artefact which is likely to become cumulatively more important as experiments progress (see Grellmann 2002;Olofsson et al 2004;Bråthen et al 2007;Ims et al 2007). An uncoupling between the magnitudes of air and soil warming is also likely to have cumulative effects on plantsoil interactions (Bardgett et al 2005), nutrient recycling and ecosystem C flux.…”

Section: Itex-specific Constraints?mentioning

confidence: 99%

Experimental approaches to predicting the future of tundra plant communities

Wookey

2008

Plant Ecology & Diversity

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Predicting the future of tundra plant communities is a major intellectual and practical challenge and it can only be successful if underpinned by an understanding of the evolutionary history and genetics of tundra plant species, their ecophysiology, and their responsiveness (both individually and as component parts of communities) to multiple environmental change drivers. This paper considers the types of experimental approaches that have been used to understand and to predict the future of tundra plant communities and ecosystems. In particular, the use of 'environmental manipulation' experiments in the field is described, and the merits and limitations of this type of approach are considered with specific reference to the International Tundra Experiment (ITEX) as an example to indicate the key principles. The approach is compared with palaeo-environmental investigations (using archives -or proxies -of past change) and the study of environmental gradients (so-called 'space-for-time substitution') to understand potential future change. Environmental manipulation experiments have limitations associated with, for example, short timescales, treatment artefacts, and trade-offs between technical sophistication and breadth of deployment in heterogeneous landscapes/regions. They do, however, provide valuable information on seasonal through decadal phenological, growth, reproductive, and ecosystem responses which have a direct bearing on ecosystem-atmosphere coupling, species interactions and, potentially, trophic cascades. Designed appropriately, they enable researchers to test specific hypotheses and to record the dynamics of ecosystem responses to change directly, thus providing a robust complement to palaeo-environmental investigations, gradient studies and ecosystem modelling.

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Reindeer influence on ecosystem processes in the tundra

Cited by 196 publications

References 50 publications

Short‐ and long‐term effects of changes in reindeer grazing pressure on tundra heath vegetation

Short‐ and long‐term effects of changes in reindeer grazing pressure on tundra heath vegetation

Variable impact of late-Quaternary megafaunal extinction in causing ecological state shifts in North and South America

Experimental approaches to predicting the future of tundra plant communities

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