| 1. |
- Brachmann, Cole, 1993, et al.
(författare)
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CH4 uptake along a successional gradient in temperate alpine soils
- 2020
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Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 0168-2563 .- 1573-515X. ; 147, s. 109-123
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Tidskriftsartikel (refereegranskat)abstract
- The effects of climate change appear to be amplified in mountains compared with lowland areas, with rapid changes in plant community composition, soil properties, and increased substrate for biological development following retreat of glaciers. Associated soil gaseous fluxes in alpine ecosystems contribute to the global balance of greenhouse gases, but methane and carbon dioxide soil fluxes and their controls are not well known. We used a dynamic closed-chamber method to measure methane and carbon dioxide fluxes along a successional gradient during the peak growing season in the North Selkirk Mountains, British Columbia, Canada. Soil physico-chemical properties, vegetation cover, and topographic variables were quantified to determine mechanisms influencing these fluxes. Mean methane uptake ranged from - 155 lg CH4-C m- 2 h-1 in well vegetated sites to zero in recently deglaciated terrain. Soil total carbon (TC) and water content were the primary drivers of methane uptake. Sites with TC greater than 4% and moisture below 0.22 water fraction by volume (w.f.v) corresponded to the strongest methane sinks. Increased vegetation cover and relatively drier soil conditions, anticipated with future climate change, suggest that methane uptake may increase in these alpine ecosystems.
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| 2. |
- Brachmann, Cole, 1993, et al.
(författare)
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Herbivore-shrub interactions influence ecosystem respiration and biogenic volatile organic compound composition in the subarctic
- 2023
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Ingår i: Biogeosciences. - 1726-4170 .- 1726-4189. ; 20, s. 4069-4086
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Tidskriftsartikel (refereegranskat)abstract
- Arctic ecosystems are warming nearly 4 times faster than the global average, which is resulting in plant community shifts and subsequent changes in biogeochemical processes such as gaseous fluxes. Additionally, herbivores shape plant communities and thereby may alter the magnitude and composition of ecosystem respiration and biogenic volatile organic compound (BVOC) emissions. Here we determine the effect of large mammalian herbivores on ecosystem respiration and BVOC emissions in two southern and two northern sites in Swedish Scandes, encompassing mountain birch (LOMB) and shrub heath (LORI) communities in the south and low-herb meadow (RIGA) and shrub heath (RIRI) communities in the north. Herbivory significantly altered BVOC composition between sites and decreased ecosystem respiration at RIGA. The difference in graminoid cover was found to have a large effect on ecosystem respiration between sites as RIGA, with the highest cover, had 35 % higher emissions than the next highest-emitting site (LOMB). Additionally, LOMB had the highest emissions of terpenes, with the northern sites having significantly lower emissions. Differences between sites were primarily due to differences in exclosure effects and soil temperature and the prevalence of different shrub growth forms. Our results suggest that herbivory has a significant effect on trace gas fluxes in a productive meadow community and that differences between communities may be driven by differences in shrub composition. Copyright:
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| 3. |
- Brachmann, Cole, 1993
(författare)
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Trophic interactions in the tundra: Impacts of large mammal herbivory on carbon processes and fungal communities
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Plant productivity is generally increasing in the Arctic as a consequence of accelerated climate change. The change in plant communities may coincide with a loss of carbon from Arctic soils due to increased decomposition and respiration. Herbivores can mediate these changes through preferential foraging on highly productive plant species, trampling, and waste deposition. Soil fungi are also a major component in these interactions and are controlled by plant community and soil conditions. Soil fungi have large impacts on the cycling of carbon in soil and its subsequent release to the atmosphere. Understanding of the effects of large mammalian herbivores on carbon processes, such as respiration and decomposition, and fungal communities is important for understanding the context of future changes in carbon storage in tundra soils. I investigated the effect of herbivory on trace gas fluxes, decomposition and stabilization of organic matter, and soil fungal communities through the use of herbivore exclusion fences in tundra communities. Herbivory reduced ecosystem respiration in a meadow community, reduced stabilization under a deciduous shrub in a heath community, reduced arbuscular mycorrhizal fungi across the Arctic, and reduced ectomycorrhizal fungi locally in Swedish tundra. The presence of herbivores on the landscape can have complex effects on carbon in tundra habitats by reducing respiration rates and limiting fast cycling arbuscular mycorrhizal fungi, while simultaneously reducing the stability of organic matter as it decomposes and locally limiting slower cycling ectomycorrhizal fungi. The relative contribution of each of these processes to carbon cycling will determine the net effect of herbivores on tundra soils. Herbivory impacts are context dependent and the net effect on soil carbon is likely related to the proportion of different tundra community types on the landscape.
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| 4. |
- Scharn, Ruud, et al.
(författare)
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Vegetation responses to 26 years of warming at Latnjajaure Field Station, northern Sweden
- 2022
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Ingår i: Arctic Science. - 2368-7460. ; 8:3, s. 858-877
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is rapidly warming high latitude and high elevation regions influencing plant community composition. Changes in vegetation composition have motivated the coordination of ecological monitoring networks across the Arctic, including the International Tundra Experiment (ITEX). We have established a long-term passive warming experiment using open-top chambers, which includes five distinct plant communities (Dry Heath; Tussock Tundra; and Dry, Mesic, and Wet Meadow). We have measured changes in plant community composition based on relative abundance differences over 26 years. In addition, relative abundance changes in response to fertilization and warming treatments were analysed based on a 7-year Community-Level Interaction Program (CLIP) experiment. The communities had distinct soil moisture conditions, leading to community specific responses of the plant growth forms (deciduous shrubs, evergreen shrubs, forbs and graminoids). Warming significantly affected growth forms, but the direction of the response was not consistent across the communities. Evidence of shrub expansion was found in nearly all communities, with soil moisture determining whether it was driven by deciduous or evergreen shrubs. Graminoids increased in relative abundance in the Dry Meadow due to warming. Growth form responses to warming are likely mediated by edaphic characteristics of the communities and their interactions with climate.
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