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- Santruckova, Hana, et al.
(författare)
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Significance of dark CO2 fixation in arctic soils
- 2018
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 119, s. 11-21
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Tidskriftsartikel (refereegranskat)abstract
- The occurrence of dark fixation of CO2 by heterotrophic microorganisms in soil is generally accepted, but its importance for microbial metabolism and soil organic carbon (C) sequestration is unknown, especially under C limiting conditions. To fill this knowledge gap, we measured dark (CO2)-C-13 incorporation into soil organic matter and conducted a C-13-labelling experiment to follow the C-13 incorporation into phospholipid fatty acids as microbial biomass markers across soil profiles of four tundra ecosystems in the northern circumpolar region, where net primary productivity and thus soil C inputs are low. We further determined the abundance of various carboxylase genes and identified their microbial origin with metagenomics. The microbial capacity for heterotrophic CO2 fixation was determined by measuring the abundance of carboxylase genes and the incorporation of C-13 into soil C following the augmentation of bioavailable C sources. We demonstrate that dark CO2 fixation occurred ubiquitously in arctic tundra soils, with increasing importance in deeper soil horizons, presumably due to increasing C limitation with soil depth. Dark CO2 fixation accounted on average for 0.4, 1.0, 1.1, and 16% of net respiration in the organic, cryoturbated organic, mineral and permafrost horizons, respectively. Genes encoding anaplerotic enzymes of heterotrophic microorganisms comprised the majority of identified carboxylase genes. The genetic potential for dark CO2 fixation was spread over a broad taxonomic range. The results suggest important regulatory function of CO2 fixation in C limited conditions. The measurements were corroborated by modeling the long-term impact of dark CO2 fixation on soil organic matter. Our results suggest that increasing relative CO2 fixation rates in deeper soil horizons play an important role for soil internal C cycling and can, at least in part, explain the isotopic enrichment with soil depth.
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| 2. |
- Varsadiya, Milan, et al.
(författare)
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Extracellular enzyme ratios reveal locality and horizon-specific carbon, nitrogen, and phosphorus limitations in Arctic permafrost soils
- 2022
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Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 0168-2563 .- 1573-515X. ; 161:2, s. 101-117
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Tidskriftsartikel (refereegranskat)abstract
- Permafrost affected soils are highly vulnerable to climate change. These soils store huge amounts of organic carbon (C), and a significant proportion of this carbon is stored in subsoil horizons where it might become available to microbial decomposition under global warming. An important factor in understanding and quantifying the C release from soils include the limitation of resources for microbes. Microbes decompose soil organic matter (SOM) by secreting extracellular enzymes into the soil, thus enzyme activity and their ratios are considered important indicators of soil nutrient availability and microbial substrate limitation. To evaluate nutrient limitation and the limitation of microbial substrate utilization, we investigated the potential enzyme activity from whole soil profiles, including topsoil, cryoturbated organic matter, mineral subsoil, and permafrost of Herschel Island (Canada) and Disko Island (Greenland). We included seven enzymes (five hydrolytic and two oxidative) and related them to bacterial and fungal gene abundance. The results showed hydrolytic enzymatic activity was strongly influenced by soil type, whereas oxidative enzymes varied between different localities. The enzyme ratios indicated that the topsoil microbial communities were C and phosphorus (P) co-limited in both localities, whereas the subsoil communities were nitrogen (N) limited from HI and C, P limited from DI. A strong positive correlation between all measured enzymes and bacterial gene abundance compared to that of fungi suggested that bacteria might play a more important role in SOM decomposition in permafrost soil horizons. This study suggests that Arctic permafrost microbial communities were not only limited by N, but also by C, P, and their co-limitation under specific conditions (i.e., higher abundance of bacteria and lower abundance of fungi).
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| 3. |
- Wild, Birgit, et al.
(författare)
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Plant-derived compounds stimulate the decomposition of organic matter in arctic permafrost soils
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Arctic ecosystems are warming rapidly, which is expected to promote soil organic matter (SOM) decomposition. In addition to the direct warming effect, decomposition can also be indirectly stimulated via increased plant productivity and plant-soil C allocation, and this so called “priming effect” might significantly alter the ecosystem C balance. In this study, we provide first mechanistic insights into the susceptibility of SOM decomposition in arctic permafrost soils to priming. By comparing 119 soils from four locations across the Siberian Arctic that cover all horizons of active layer and upper permafrost, we found that an increased availability of plant-derived organic C particularly stimulated decomposition in subsoil horizons where most of the arctic soil carbon is located. Considering the 1,035 Pg of arctic soil carbon, such an additional stimulation of decomposition beyond the direct temperature effect can accelerate net ecosystem C losses, and amplify the positive feedback to global warming.
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