| 1. |
- 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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| 2. |
- 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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| 3. |
- Falk, Julie Maria, et al.
(författare)
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Effects of simulated increased grazing on carbon allocation patterns in a high arctic mire
- 2014
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Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 1573-515X .- 0168-2563. ; 119:1-3, s. 229-244
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Tidskriftsartikel (refereegranskat)abstract
- Herbivory is an important part of most ecosystems, and grazing alone can have a considerable impact on the ecosystems carbon balance with both direct and indirect effects. Removal of above-ground biomass by consumption of herbivores will change the below-ground carbon stock; the reduction of litter that goes into the ground will influence the total ecosystem carbon content. Little is however known about how plant-herbivory interactions effect the carbon balance, in particular methane emissions, of high arctic mires. We hypothesized that increased grazing pressure will change carbon allocation patterns resulting in decreased net ecosystem uptake of carbon and subsequently in lower methane emissions. An in-situ field experiment was conducted over 3 years in a high arctic mire at Zackenberg in NE Greenland. The experiment consisted of three treatments, with five replicates of each (1) control, (2) vascular plants were removed (NV), (3) clipped twice each growing season in order to simulate increased muskox grazing. Immediately after the initiation of the experiment net ecosystem uptake of CO2 decreased in clipped plots (mean total decrease for the three following years was 35 %). One year into the experiment a significantly lower CH4 emission was observed in these plots, the total mean reduction for the following 2 years was 26 %. Three years into the experiment significantly lower substrate (acetic acid) availability for CH4 production was observed (27 % reduction). NV plots had a mean decrease in CO2 uptake of 113 %, a 62 % decrease in ecosystem respiration and an 84 % decrease in CH4 emission (mean of all 3 years). Our study shows that increased grazing pressure in a high arctic mire can lead to significant changes in the carbon balance, with lower CO2 uptake leading to lower production of substrate for CH4 formation and in lower CH4 emission.
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