| 1. |
- Alatalo, Juha M., et al.
(författare)
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Impacts of twenty years of experimental warming on soil carbon, nitrogen, moisture and soil mites across alpine/subarctic tundra communities
- 2017
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Ingår i: Scientific Reports. - : Macmillan Publishers Ltd.. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- High-altitude and alpine areas are predicted to experience rapid and substantial increases in future temperature, which may have serious impacts on soil carbon, nutrient and soil fauna. Here we report the impact of 20 years of experimental warming on soil properties and soil mites in three contrasting plant communities in alpine/subarctic Sweden. Long-term warming decreased juvenile oribatid mite density, but had no effect on adult oribatids density, total mite density, any major mite group or the most common species. Long-term warming also caused loss of nitrogen, carbon and moisture from the mineral soil layer in mesic meadow, but not in wet meadow or heath or from the organic soil layer. There was a significant site effect on the density of one mite species, Oppiella neerlandica, and all soil parameters. A significant plot-scale impact on mites suggests that small-scale heterogeneity may be important for buffering mites from global warming. The results indicated that juvenile mites may be more vulnerable to global warming than adult stages. Importantly, the results also indicated that global warming may cause carbon and nitrogen losses in alpine and tundra mineral soils and that its effects may differ at local scale.
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| 2. |
- Alsterberg, Christian, 1982, et al.
(författare)
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Habitat diversity and ecosystem multifunctionality-The importance of direct and indirect effects
- 2017
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 3:2
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Tidskriftsartikel (refereegranskat)abstract
- Ecosystems worldwide are facing habitat homogenization due to human activities. Although it is commonly proposed that such habitat homogenization can have negative repercussions for ecosystem functioning, this question has yet to receive explicit scientific attention. We expand on the framework for evaluating the functional consequences of bio-diversity loss by scaling up from the level of species to the level of the entire habitats. Just as species diversity generally fosters ecosystem functioning through positive interspecies interactions, we hypothesize that different habitats within ecosystems can facilitate each other through structural complementarity and through exchange of material and energy across habitats. We show that experimental ecosystems comprised of a diversity of habitats show higher levels of multiple ecosystem functions than ecosystems with low habitat diversity. Our results demonstrate that the effect of habitat diversity on multifunctionality varies with season; it has direct effects on ecosystem functioning in summer and indirect effects, via changes in species diversity, in autumn, but no effect in spring. We propose that joint consideration of habitat diversity and species diversity will prove valuable for both environmental management and basic research.
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| 3. |
- Cederlund, Harald, et al.
(författare)
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Soil carbon quality and nitrogen fertilization structure bacterial communities with predictable responses of major bacterial phyla
- 2014
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Ingår i: Applied Soil Ecology. - : Elsevier BV. - 0929-1393 .- 1873-0272. ; 84, s. 62-68
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Tidskriftsartikel (refereegranskat)abstract
- Agricultural practices affect the soil ecosystem in multiple ways and the soil microbial communities represent an integrated and dynamic measure of soil status. Our aim was to test whether the soil bacterial community and the relative abundance of major bacterial phyla responded predictably to long-term organic amendments representing different carbon qualities (peat and straw) in combination with nitrogen fertilization levels and if certain bacterial groups were indicative of specific treatments. We hypothesized that the long-term treatments had created distinctly different ecological niches for soil bacteria, suitable for either fast-growing copiotrophic bacteria, or slow-growing oligotrophic bacteria. Based on terminal-restriction fragment length polymorphism of the 16S rRNA genes from the total soil bacterial community and taxa-specific quantitative real-time PCR of seven different groups, all treatments significantly affected the community structure, but nitrogen fertilization was the most important driver for changes in the relative abundances of the studied taxa. According to an indicator species analysis, the changes were largely explained by the decline in the relative abundances of Acidobacteria, Gemmatimonadetes and Verrucomicrobia with nitrogen fertilization. Conditions more favourable for copiotrophic life strategies were indicated in these plots by the decreased metabolic quotient, i.e. the ratio between basal respiration rate and soil biomass. Apart from the Alphaproteobacteria that were significantly associated with peat, no taxa were indicative of organic amendment in general. However, several significant indicators of both peat and straw were identified among the terminal restriction fragments suggesting that changes induced by the organic amendments were mainly manifested at a lower taxonomical level. Our findings strengthen the proposition that certain higher bacterial taxa adapt in an ecologically coherent way in response to changes induced by fertilization. (C) 2014 Elsevier B.V. All rights reserved.
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| 4. |
- Choudhury, Maidul, et al.
(författare)
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Disentangling the roles of plant functional diversity and plaint traits in regulating plant nitrogen accumulation and denitrification in freshwaters
- 2022
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 36, s. 921-932
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Tidskriftsartikel (refereegranskat)abstract
- 1. There is a growing recognition that functional measures of diversity, based on quantification of functionally important species traits, are useful for explaining variation in ecosystem processes. However, the mechanisms linking functional diversity to different processes remain poorly understood, hindering development of a predictive framework for ecosystem functioning based on species traits.2. The current understanding of how the functional traits of aquatic plants (macrophytes) affect nitrogen (N) cycling by regulating microbial communities and their activity in freshwater habitats is particularly limited. Denitrifying bacteria are typically associated with the roots of both aquatic and terrestrial plants and denitrification is the main cause of loss of N from ecosystems. Disentangling the interplay between plants and microbial denitrifiers is key to understanding variation in rates of denitrification from local to landscape scales.3. In a mesocosm experiment, we varied the species richness (monocultures or two-species mixtures) and composition of macrophytes. We quantified effects of both macrophyte functional diversity, quantified as functional trait dissimilarity, and functional trait composition, quantified as community weighted mean trait values, on N removal in wetlands. We used structural equation modelling to disentangle the direct and indirect influences of traits on N accumulation in plant biomass, denitrification activity and abundance of key bacterial denitrification genes (nirS and nirK).4. Both functional diversity and functional trait composition regulated N removal, explaining 70%-94% variation in the underlying ecosystem processes. Increased macrophyte functional diversity increased plant N accumulation, and indirectly enhanced denitrification by increasing denitrification gene abundance. Among traits, greater plant relative growth rates, specific leaf area and above-ground biomass increased plant N accumulation. Denitrification activity increased with increasing below-ground biomass but decreased with increasing root diameter.5. These findings improve our understanding of N removal in freshwater wetlands dominated by macrophytes, and have broad ecological implications for wetland management targeting enhanced ecosystem services. Our results highlight the potential for optimizing denitrification and plant N accumulation in wetlands and thereby improving water purification by increasing macrophyte functional diversity and ensuring the presence of key traits in macrophyte assemblages.
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| 5. |
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| 6. |
- Guasconi, Daniela, 1992-, et al.
(författare)
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Vegetation, topography, and soil depth drive microbial community structure in two Swedish grasslands
- 2023
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Ingår i: FEMS Microbiology Ecology. - 0168-6496 .- 1574-6941. ; 99:8
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Tidskriftsartikel (refereegranskat)abstract
- Soil microbial diversity and community composition are shaped by various factors linked to land management, topographic position,and vegetation. To study the effects of these drivers, we characterized fungal and bacterial communities from bulk soil at four soildepths ranging from the surface to below the rooting zone of two Swedish grasslands with differing land-use histories, each includingboth an upper and a lower catenary position. We hypothesized that differences in plant species richness and plant functional groupcomposition between the four study sites would drive the variation in soil microbial community composition and correlate withmicrobial diversity, and that microbial biomass and diversity would decrease with soil depth following a decline in resource availability.While vegetation was identified as the main driver of microbial community composition, the explained variation was significantlyhigher for bacteria than for fungi, and the communities differed more between grasslands than between catenary positions. Microbialbiomass derived from DNA abundance decreased with depth, but diversity remained relatively stable, indicating diverse microbialcommunities even below the rooting zone. Finally, plant-microbial diversity correlations were significant only for specific plant andfungal functional groups, emphasizing the importance of functional interactions over general species richness
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| 7. |
- Hallin, Sara, et al.
(författare)
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Shaping of soil microbial communities by plants does not translate into specific legacy effects on organic carbon mineralization
- 2021
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 163
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Tidskriftsartikel (refereegranskat)abstract
- Plants shape soil microbial communities through their root architecture, their rhizodeposits and return of dead plant material to the soil. These interactions can have a strong influence on the soil organic carbon dynamics. However, it is unclear whether the plant species effects on the soil microbial community could influence the organic carbon mineralization through plant legacy effects. Therefore, we examined how and to what extent a short-term plant growing phase affected the total and active soil microorganisms and through a possible plant legacy, also the mineralization of soil organic carbon, a central ecosystem function. Using a controlled pot experiment, we first showed that the two phylogenetically distinct plants, Arabidopsis thaliana and Triticum aestivum, differently shaped the soil microbial communities when recruiting from the same soil community. Although both plants recruited plant-growth promoting bacteria in the vicinity of their roots, A. thaliana had a stronger effect than T. aestivum and also recruited saprophytic fungi, while inhibiting fungal pathogens. Due to plant legacy effects on the soil microbial communities, different microbial successions occurred in the two previously planted soils when subjected to plant litter. By contrast, plant legacy effects on soil basal respiration were not plant-specific, with basal respiration increasing similarly in both cases and moreover did not translate to changes in litter carbon mineralization in the short-term of 49 days. Our results suggest that the soil nutrient dynamics rather than changes in soil microbial community composition drive the organic carbon mineralization of added litter. The present study brings new insights in how the relationships between plants, microorganisms and soil nutrient dynamics affect litter carbon cycling.
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| 8. |
- Hallin, Sara, et al.
(författare)
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Site-specific responses of fungal and bacterial abundances to experimental warming in litter and soil across arctic and alpine tundra
- 2021
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Ingår i: Arctic science. - : Canadian Science Publishing. - 2368-7460.
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Tidskriftsartikel (refereegranskat)abstract
- Vegetation change of the Arctic tundra due to global warming is a well-known process, but the implication for the belowground microbial communities, key in nutrient cycling and decomposition, is poorly understood. We characterized the fungal and bacterial abundances in litter and soil layers across 16 warming experimental sites at 12 circumpolar locations. We investigated the relationship between microbial abundances and nitrogen (N) and carbon (C) isotopic signatures, indicating shifts in microbial processes with warming. Microbial abundances were 2–3 orders of magnitude larger in litter than in soil. Local, site-dependent responses of microbial abundances were variable, and no general effect of warming was detected. The only generalizable trend across sites was a dependence between the warming response ratios and C:N ratio in controls, highlighting a legacy of the vegetation on the microbial response to warming. We detected a positive effect of warming on the litter mass and δ15N, which was linked to bacterial abundance under warmed conditions. This effect was stronger in experimental sites dominated by deciduous shrubs, suggesting an altered bacterial N-cycling with increased temperatures, mediated by the vegetation, and with possible consequences on ecosystem feedbacks to climate change.
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| 9. |
- Hellman, Maria, et al.
(författare)
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External carbon addition for enhancing denitrification modifies bacterial community composition and affects CH4 and N2O production in sub-arctic mining pond sediments
- 2019
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Ingår i: Water Research. - : Elsevier. - 0043-1354 .- 1879-2448. ; 158, s. 22-33
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Tidskriftsartikel (refereegranskat)abstract
- Explosives used in mining operations release reactive nitrogen (N) that discharge into surrounding waters. Existing pond systems at mine sites could be used for N removal through denitrification and we investigated capacity in tailings and clarification pond sediments at an iron-ore mine site. Despite differences in microbial community structure in the two ponds, the potential denitrification rates were similar, although carbon limited. Therefore, a microcosm experiment in which we amended sediment from the clarification pond with acetate, cellulose or green algae as possible carbon sources was conducted during 10 weeks under denitrifying conditions. Algae and acetate treatments showed efficient nitrate removal and increased potential denitrification rates, whereas cellulose was not different from the control. Denitrifiers were overall more abundant than bacteria performing dissimilatory nitrate reduction to ammonium (DNRA) or anaerobic ammonium oxidation, although DNRA bacteria increased in the algae treatment and this coincided with accumulation of ammonium. The algae addition also caused higher emissions of methane (CH4) and nitrous oxide (N2O). The bacterial community in this treatment had a large proportion of Bacteroidia, sulfate reducing taxa and bacteria known as fermenters. Functional gene abundances indicated an imbalance between organisms that produce N2O in relation to those that can reduce it, with the algae treatment showing the lowest relative capacity for N2O reduction. These findings show that pond sediments have the potential to contribute to mitigating nitrate levels in water from mining industry, but it is important to consider the type of carbon supply as it affects the community composition, which in turn can lead to uwanted processes and increased greenhouse gas emissions.
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| 10. |
- Hellman, Maria, et al.
(författare)
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Microbial succession and denitrifying woodchip bioreactor performance at low water temperatures
- 2024
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Ingår i: Journal of Environmental Management. - : Elsevier. - 0301-4797 .- 1095-8630. ; 356
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Tidskriftsartikel (refereegranskat)abstract
- Mining activities are increasingly recognized for contributing to nitrogen (N) pollution and possibly also to emissions of the greenhouse gas nitrous oxide (N2O) due to undetonated, N-based explosives. A woodchip denitrifying bioreactor, installed to treat nitrate-rich leachate from waste rock dumps in northern Sweden, was monitored for two years to determine the spatial and temporal distribution of microbial communities, including the genetic potential for different N transformation processes, in pore water and woodchips and how this related to reactor N removal capacity. About 80 and 65 % of the nitrate was removed during the first and second operational year, respectively. There was a succession in the microbial community over time and in space along the reactor length in both pore water and woodchips, which was reflected in reactor performance. Nitrate ammonification likely had minimal impact on N removal efficiency due to the low production of ammonium and low abundance of the key gene nrfA in ammonifiers. Nitrite and N2O were formed in the bioreactor and released in the effluent water, although direct N2O emissions from the surface was low. That these unwanted reactive N species were produced at different times and locations in the reactor indicate that the denitrification pathway was temporally as well as spatially separated along the reactor length. We conclude that the succession of microbial communities in woodchip denitrifying bioreactors treating mining water develops slowly at low tem-perature, which impacts reactor performance.
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