| 1. |
- Cornelissen, Johannes H C, et al.
(författare)
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Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes
- 2007
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:7, s. 619-627
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Tidskriftsartikel (refereegranskat)abstract
- Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide.Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.
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| 2. |
- Barrio, Isabel C., et al.
(författare)
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Background invertebrate herbivory on dwarf birch (Betula glandulosa-nana complex) increases with temperature and precipitation across the tundra biome
- 2017
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Ingår i: Polar Biology. - : Springer. - 0722-4060 .- 1432-2056. ; 40:11, s. 2265-2278
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Tidskriftsartikel (refereegranskat)abstract
- Chronic, low intensity herbivory by invertebrates, termed background herbivory, has been understudied in tundra, yet its impacts are likely to increase in a warmer Arctic. The magnitude of these changes is however hard to predict as we know little about the drivers of current levels of invertebrate herbivory in tundra. We assessed the intensity of invertebrate herbivory on a common tundra plant, the dwarf birch (Betula glandulosa-nana complex), and investigated its relationship to latitude and climate across the tundra biome. Leaf damage by defoliating, mining and gall-forming invertebrates was measured in samples collected from 192 sites at 56 locations. Our results indicate that invertebrate herbivory is nearly ubiquitous across the tundra biome but occurs at low intensity. On average, invertebrates damaged 11.2% of the leaves and removed 1.4% of total leaf area. The damage was mainly caused by external leaf feeders, and most damaged leaves were only slightly affected (12% leaf area lost). Foliar damage was consistently positively correlated with mid-summer (July) temperature and, to a lesser extent, precipitation in the year of data collection, irrespective of latitude. Our models predict that, on average, foliar losses to invertebrates on dwarf birch are likely to increase by 6-7% over the current levels with a 1 degrees C increase in summer temperatures. Our results show that invertebrate herbivory on dwarf birch is small in magnitude but given its prevalence and dependence on climatic variables, background invertebrate herbivory should be included in predictions of climate change impacts on tundra ecosystems.
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| 3. |
- Barrio, Isabel C., et al.
(författare)
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Publisher Correction to : Background invertebrate herbivory on dwarf birch (Betula glandulosa-nana complex) increases with temperature and precipitation across the tundra biome (vol 40, pg 2265, 2017)
- 2018
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Ingår i: Polar Biology. - : Springer. - 0722-4060 .- 1432-2056. ; 41:8, s. 1653-1654
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Tidskriftsartikel (refereegranskat)abstract
- The above mentioned article was originally scheduled for publication in the special issue on Ecology of Tundra Arthropods with guest editors Toke T. Hoye . Lauren E. Culler. Erroneously, the article was published in Polar Biology, Volume 40, Issue 11, November, 2017. The publisher sincerely apologizes to the guest editors and the authors for the inconvenience caused.
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| 4. |
- Bernes, Claes, et al.
(författare)
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What are the impacts of reindeer/caribou (Rangifer tarandus L.) on arctic and alpine vegetation? : A systematic review protocol
- 2013
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Ingår i: Environmental Evidence. - : BioMed Central (BMC). - 2047-2382. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- Background: Reindeer and caribou (both belonging to the species Rangifer tarandus L.) are among the most important large herbivores in Eurasia’s and North America’s arctic, alpine and boreal zones. In Sweden, the impact of reindeer grazing on arctic and alpine vegetation has recently been re-evaluated. In the 1990s, records of grazing-related vegetation degradation helped to form a widespread perception that some mountain areas were overgrazed. However, later analyses have shown no evidence of large-scale overutilisation of reindeer ranges in the Swedish mountains.The present-day consensus is that overgrazing has been temporary and local, and that it rarely has caused permanent damage, but it is imperative to examine the scientific support for these views. Moreover, the Swedish Parliament has adopted an environmental quality objective according to which it is essential to preserve ‘a mountain landscape characterised by grazing’. No details have been given on how this goal is to be interpreted, which is another reason why the significance of reindeer grazing for arctic/alpine vegetation needs to be assessed.This protocol presents the methodology that will be used in a systematic review of the impact of reindeer herbivory in arctic and alpine ecosystems. The focus will be on Fennoscandia, but data from other parts of the range of R. tarandus will be used when deemed appropriate.Methods: The review will be based on primary field studies that compare vegetation subject to different degrees of reindeer/caribou herbivory (including grazing and browsing as well as trampling). Such comparisons can be either temporal, spatial or both. The review will cover impacts of herbivory in arctic, subarctic, alpine and subalpine areas (including the forest-tundra ecotone) across the range of R. tarandus, but not in boreal forests. Relevant aspects of vegetation include cover (abundance), biomass, diversity (e.g. species richness), structure, composition (including functional groups) and productivity.
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| 5. |
- Björkman, Anne, 1981, et al.
(författare)
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Plant functional trait change across a warming tundra biome
- 2018
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 562:7725, s. 57-62
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Tidskriftsartikel (refereegranskat)abstract
- The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature–trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.
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| 6. |
- Bokhorst, Stef Frederik, et al.
(författare)
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Variable temperature effects of Open Top Chambers at polar and alpine sites explained by irradiance and snow depth
- 2013
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 19:1, s. 64-74
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Forskningsöversikt (refereegranskat)abstract
- Environmental manipulation studies are integral to determining biological consequences of climate warming. Open Top Chambers (OTCs) have been widely used to assess summer warming effects on terrestrial biota, with their effects during other seasons normally being given less attention even though chambers are often deployed year-round. In addition, their effects on temperature extremes and freeze-thaw events are poorly documented. To provide robust documentation of the microclimatic influences of OTCs throughout the year, we analysed temperature data from 20 studies distributed across polar and alpine regions. The effects of OTCs on mean temperature showed a large range (-0.9 to 2.1 degrees C) throughout the year, but did not differ significantly between studies. Increases in mean monthly and diurnal temperature were strongly related (R-2 = 0.70) with irradiance, indicating that PAR can be used to predict the mean warming effect of OTCs. Deeper snow trapped in OTCs also induced higher temperatures at soil/vegetation level. OTC-induced changes in the frequency of freeze-thaw events included an increase in autumn and decreases in spring and summer. Frequency of high-temperature events in OTCs increased in spring, summer and autumn compared with non-manipulated control plots. Frequency of low-temperature events was reduced by deeper snow accumulation and higher mean temperatures. The strong interactions identified between aspects of ambient environmental conditions and effects of OTCs suggest that a detailed knowledge of snow depth, temperature and irradiance levels enables us to predict how OTCs will modify the microclimate at a particular site and season. Such predictive power allows a better mechanistic understanding of observed biotic response to experimental warming studies and for more informed design of future experiments. However, a need remains to quantify OTC effects on water availability and wind speed (affecting, for example, drying rates and water stress) in combination with microclimate measurements at organism level.
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| 7. |
- Elmendorf, Sarah C., et al.
(författare)
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Global assessment of experimental climate warming on tundra vegetation : heterogeneity over space and time
- 2012
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 15:2, s. 164-175
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Forskningsöversikt (refereegranskat)abstract
- Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation and associated ecosystem consequences have the potential to be much greater than we have observed to date.
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| 8. |
- Elmendorf, Sarah C., et al.
(författare)
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Plot-scale evidence of tundra vegetation change and links to recent summer warming
- 2012
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Ingår i: Nature Climate Change. - : Nature Publishing Group. - 1758-678X .- 1758-6798. ; 2:6, s. 453-457
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Tidskriftsartikel (refereegranskat)abstract
- Temperature is increasing at unprecedented rates across most of the tundra biome. Remote-sensing data indicate that contemporary climate warming has already resulted in increased productivity over much of the Arctic, but plot-based evidence for vegetation transformation is not widespread. We analysed change in tundra vegetation surveyed between 1980 and 2010 in 158 plant communities spread across 46 locations.We found biome-wide trends of increased height of the plant canopy and maximum observed plant height for most vascular growth forms; increased abundance of litter; increased abundance of evergreen, low-growing and tall shrubs; and decreased abundance of bare ground. Intersite comparisons indicated an association between the degree of summer warming and change in vascular plant abundance, with shrubs, forbs and rushes increasing with warming. However, the association was dependent on the climate zone, the moisture regime and the presence of permafrost. Our data provide plot-scale evidence linking changes in vascular plant abundance to local summer warming in widely dispersed tundra locations across the globe.
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| 9. |
- Elphinstone, Cassandra, et al.
(författare)
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Multiple Pleistocene refugia for Arctic Bell-Heather revealed with genomic analyses of modern and historic plants
- 2024
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Ingår i: Journal of Biogeography. - 0305-0270 .- 1365-2699.
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Arctic plants survived the Pleistocene glaciations in unglaciated refugia. The number, ages, and locations of these refugia are often unclear. We use high-resolution genomic data from present-day and Little-Ice-Age populations of Arctic Bell-Heather to re-evaluate the biogeography of this species and determine whether it had multiple independent refugia or a single refugium in Beringia. Location: Circumpolar Arctic and Coastal British Columbia (BC) alpine. Taxon: Cassiope tetragona L., subspecies saximontana and tetragona, outgroup C. mertensiana (Ericaceae). Methods: We built genotyping-by-sequencing (GBS) libraries using Cassiope tetragona tissue from 36 Arctic locations, including two ~250- to 500-year-old populations collected under glacial ice on Ellesmere Island, Canada. We assembled a de novo GBS reference to call variants. Population structure, genetic diversity and demography were inferred from PCA, ADMIXTURE, fastsimcoal2, SplitsTree, and several population genomics statistics. Results: Population structure analyses identified 4–5 clusters that align with geographic locations. Nucleotide diversity was highest in Beringia and decreased eastwards across Canada. Demographic coalescent analyses dated the following splits with Alaska: BC subspecies saximontana (5 mya), Russia (~1.4 mya), Europe (>200–600 kya), and Greenland (~60 kya). Northern Canada populations appear to have formed during the current interglacial (7–9 kya). Admixture analyses show genetic variants from Alaska appear more frequently in present-day than historic plants on Ellesmere Island. Conclusions: Population and demographic analyses support BC, Alaska, Russia, Europe and Greenland as all having had independent Pleistocene refugia. Northern Canadian populations appear to be founded during the current interglacial with genetic contributions from Alaska, Europe and Greenland. We found evidence, on Ellesmere Island, for continued recent gene flow in the last 250–500 years. These results suggest that a re-analysis of other Arctic species with shallow population structure using higher resolution genomic markers and demographic analyses may help reveal deeper structure and other circumpolar glacial refugia.
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| 10. |
- Hofgaard, Annika, et al.
(författare)
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Comparing warming and grazing effects on birch growth in an alpine environment : a 10-year experiment
- 2010
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Ingår i: Plant Ecology & Diversity. - : Informa UK Limited. - 1755-0874 .- 1755-1668. ; 3:1, s. 19-27
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Tidskriftsartikel (refereegranskat)abstract
- Background : Tree encroachment of arctic tundra and alpine vegetation is a generally predicted response to climate warming. However, herbivory plays an important role in structuring these ecosystems and their responses to warming. Aims : To experimentally test how grazing and increased growing season temperature influence growth, physiognomy and stature of birch in the alpine zone. Methods: Trait responses of naturally regenerated birch saplings to warming (open-top chambers), and changed grazing regime (exclosures) were compared with those growing in unmanipulated conditions over a 10-year period (1999–2008). The effect of treatment over time and differences between treatments were analysed with repeated measures GLM (Generalised Linear Model) and simple contrasts in GLM. Results: Warming alone had no major effect on trait responses, however, significantly smaller leaves and an increased number of short shoots indicated warming-related growth constraints. Grazing showed a strong controlling effect on most traits, conserving low stature sapling stage characterised by fewer shoots and larger leaves, compared with non-grazed treatments. Conclusions: Although derived from one experimental site, the results point to a grazing-controlled response to environmental change, with climate (warming) as a secondary driver. This herbivore-driven masking of expected climate-driven tree expansion emphasises the necessity to consider changes in grazing regimes along with climate change, in order to avoid misleading interpretations regarding climate-driven tundra encroachment.
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