| 1. |
- Eshghi Sahraei, Shadi, et al.
(author)
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Effects of operational taxonomic unit inference methods on soil microeukaryote community analysis using long‐read metabarcoding
- 2022
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In: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 12:3
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Journal article (peer-reviewed)abstract
- Long amplicon metabarcoding has opened the door for phylogenetic analysis of the largely unknown communities of microeukaryotes in soil. Here, we amplified and sequenced the ITS and LSU regions of the rDNA operon (around 1500 bp) from grassland soils using PacBio SMRT sequencing. We tested how three different methods for generation of operational taxonomic units (OTUs) effected estimated richness and identified taxa, and how well large-scale ecological patterns associated with shifting environmental conditions were recovered in data from the three methods. The field site at Kungsängen Nature Reserve has drawn frequent visitors since Linnaeus's time, and its species rich vegetation includes the largest population of Fritillaria meleagris in Sweden. To test the effect of different OTU generation methods, we sampled soils across an abrupt moisture transition that divides the meadow community into a Carex acuta dominated plant community with low species richness in the wetter part, which is visually distinct from the mesic-dry part that has a species rich grass-dominated plant community including a high frequency of F. meleagris. We used the moisture and plant community transition as a framework to investigate how detected belowground microeukaryotic community composition was influenced by OTU generation methods. Soil communities in both moisture regimes were dominated by protists, a large fraction of which were taxonomically assigned to Ciliophora (Alveolata) while 30%–40% of all reads were assigned to kingdom Fungi. Ecological patterns were consistently recovered irrespective of OTU generation method used. However, different methods strongly affect richness estimates and the taxonomic and phylogenetic resolution of the characterized community with implications for how well members of the microeukaryotic communities can be recognized in the data.
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| 2. |
- Hytteborn, Håkan, et al.
(author)
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Spatial heterogeneity ensures long-term stability in vegetation and Fritillaria meleagris flowering in Uppsala Kungsäng, a semi-natural meadow
- 2023
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 18:3
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Journal article (peer-reviewed)abstract
- Semi-natural grasslands are becoming increasingly rare, and their vegetation may be affected by environmental changes and altered management. At Kungsängen Nature Reserve, a wet to mesic semi-natural meadow near Uppsala, Sweden, we analysed long-term changes in the vegetation using data from 1940, 1982, 1995 and 2016. We also analysed the spatial and temporal dynamics in the Fritillaria meleagris population based on countings of flowering individuals in 1938, 1981–1988 and 2016–2021. Between 1940 and 1982 the wet part of the meadow became wetter, which led to an increased cover of Carex acuta and pushed the main area of flowering of F. meleagris up towards the mesic part. Annual variation in the flowering propensity of F. meleagris (in May) was affected by temperature and precipitation in the phenological phases of growth and bud initiation (June in the previous year), shoot development (September in the previous year) and initiation of flowering (March–April). However, the response to weather was in opposite directions in the wet and mesic parts of the meadow, and the flowering population showed large year-to-year variation but no long-term trend. Variation in management (poorly documented) led to changes in different parts of the meadow, but the overall composition of the vegetation, species richness and diversity changed little after 1982. Species richness and species composition of the meadow vegetation, and the long-term stability of the F. meleagris population are maintained by the variation in wetness, highlighting the importance of spatial heterogeneity as an insurance against biodiversity loss in semi-natural grasslands and nature reserves generally.
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| 3. |
- Bengtsson, Fia, 1986-, et al.
(author)
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Environmental drivers of Sphagnum growth in peatlands across the Holarctic region
- 2021
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In: Journal of Ecology. - : John Wiley & Sons. - 0022-0477 .- 1365-2745. ; 109:1, s. 417-431
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Journal article (peer-reviewed)abstract
- The relative importance of global versus local environmental factors for growth and thus carbon uptake of the bryophyte genusSphagnum-the main peat-former and ecosystem engineer in northern peatlands-remains unclear. We measured length growth and net primary production (NPP) of two abundantSphagnumspecies across 99 Holarctic peatlands. We tested the importance of previously proposed abiotic and biotic drivers for peatland carbon uptake (climate, N deposition, water table depth and vascular plant cover) on these two responses. Employing structural equation models (SEMs), we explored both indirect and direct effects of drivers onSphagnumgrowth. Variation in growth was large, but similar within and between peatlands. Length growth showed a stronger response to predictors than NPP. Moreover, the smaller and denserSphagnum fuscumgrowing on hummocks had weaker responses to climatic variation than the larger and looserSphagnum magellanicumgrowing in the wetter conditions. Growth decreased with increasing vascular plant cover within a site. Between sites, precipitation and temperature increased growth forS. magellanicum. The SEMs indicate that indirect effects are important. For example, vascular plant cover increased with a deeper water table, increased nitrogen deposition, precipitation and temperature. These factors also influencedSphagnumgrowth indirectly by affecting moss shoot density. Synthesis. Our results imply that in a warmer climate,S. magellanicumwill increase length growth as long as precipitation is not reduced, whileS. fuscumis more resistant to decreased precipitation, but also less able to take advantage of increased precipitation and temperature. Such species-specific sensitivity to climate may affect competitive outcomes in a changing environment, and potentially the future carbon sink function of peatlands.
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| 4. |
- Bengtsson, Fia, et al.
(author)
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Mechanisms behind species-specific water economy responses to water level drawdown in peat mosses
- 2020
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In: Annals of Botany. - : Oxford University Press (OUP). - 0305-7364 .- 1095-8290. ; 126:2, s. 219-230
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Journal article (peer-reviewed)abstract
- Background and AimsThe ecosystem engineers Sphagnum (peat mosses) are responsible for sequestering a large proportion of carbon in northern peatlands. Species may respond differently to hydrological changes, and water level changes may lead to vegetation shifts in peatlands, causing them to revert from sinks to sources of carbon. We aimed to compare species-specific responses to water level drawdown within Sphagnum, and investigate which traits affect water economy in this genus.MethodsIn a mesocosm experiment, we investigated how water level drawdown affected water content (WC) in the photosynthetically active apex of the moss and maximum quantum yield of photosystem II (i.e. Fv/Fm) of 13 Sphagnum species. Structural traits were measured, and eight anatomical traits were quantified from scanning electron microscopy micrographs.Key ResultsMixed-effects models indicated that at high water level, large leaves were the most influential predictor of high WC, and at low water level WC was higher in species growing drier in the field, with larger hyaline cell pore sizes and total pore areas associated with higher WC. Higher stem and peat bulk density increased WC, while capitulum mass per area and numerical shoot density did not. We observed a clear positive relationship between Fv/Fm and WC in wet-growing species.ConclusionsWhile we found that most hummock species had a relatively high water loss resistance, we propose that some species are able to maintain a high WC at drawdown by storing large amounts of water at a high water level. Our result showing that leaf traits are important warrants further research using advanced morphometric methods. As climate change may lead to more frequent droughts and thereby water level drawdowns in peatlands, a mechanistic understanding of species-specific traits and responses is crucial for predicting future changes in these systems.
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| 5. |
- Colson, Daniel W., et al.
(author)
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Six Decades of Changes in Pool Characteristics on a Concentric-Patterned Raised Bog
- 2023
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In: Ecosystems. - 1432-9840 .- 1435-0629.
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Journal article (peer-reviewed)abstract
- Raised bogs are wetland ecosystems which, under the right climatic conditions, feature patterns of pool hollows and hummock ridges. The relative cover and the spatial arrangement of pool and ridge microforms are thought to be influential on peatland atmosphere carbon gas fluxes and plant biodiversity. The mechanisms responsible for the formation and maintenance of pools, and the stability of these features in response to warming climates, remain topics of ongoing research. We employed historical aerial imagery, combined with a contemporary uncrewed aerial vehicle survey, to study 61 years of changes in pools at a patterned raised bog in central Sweden. We used a pool inheritance method to track individual pools between image acquisition dates throughout the time series. These data show a rapid loss of open-water pool area during the study period, primarily due to overgrowth of open-water pools by Sphagnum. We postulate that these changes are driven by ongoing climate warming that is accelerating Sphagnum colonisation. Open-water pool area declined by 26.8% during the study period, equivalent to a loss of 1001 m2 y−1 across the 150-hectare site. This is contradictory to an existing theory that states pools are highly stable, once formed, and can only convert to a terrestrial state through catastrophic drainage. The pool inheritance analysis shows that smaller pools are liable to become completely terrestrialised and expire. Our findings form part of a growing body of evidence for the loss of open-water habitats in peatlands across the boreal and elsewhere.
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| 6. |
- Fonturbel, Francisco E., et al.
(author)
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Cryptic interactions revisited from ecological networks : Mosses as a key link between trees and hummingbirds
- 2021
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In: Functional Ecology. - : John Wiley & Sons. - 0269-8463 .- 1365-2435. ; 35:1, s. 226-238
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Journal article (peer-reviewed)abstract
- Ecological interactions are the glue of biodiversity, structuring communities and determining their functionality. However, our knowledge about ecological interactions is usually biased against cryptic interactions (i.e. overlooked interactions involving inconspicuous species). Mosses are a neglected component in community ecology despite being diverse and abundant in boreal and temperate forests. Therefore, the cryptic relationships of trees as hosts for epiphytic mosses, and vertebrates using mosses as nesting material, may have important consequences for community structuring. We built species- and individual-based ecological networks to characterise tree-moss associations in 120 tree individuals representing 13 species, which hosted 19 moss species. We also used those ecological networks to simulate the effects of non-random extinctions due to selective logging, to assess the presence of moss species in hummingbird nests (30 nests), whether these mosses were a subset of those found on the trees if moss diversity varies with tree height and whether these moss-tree relationships are phylogenetically constrained. We found a nested pattern in the tree-moss network. Taller trees were the most connected, with tree height positively related to number of moss species, network degree and centrality. Extinction simulations showed changes in network topology, with the strongest effect from the removal of the most connected tree species. However, tree and moss networks were not influenced by phylogenetic relatedness. The hummingbirdSephanoides sephaniodesselectively collected mosses; the moss species used as nesting material by hummingbirds were a subset of available species. These complex relationships among trees, birds and mosses underpin the importance of neglected components in the community. We found that tree-moss associations were non-random, showing a positive relationship between tree height and moss diversity. Those associations are the reflection of preferences beyond relative abundances in the forest, and the removal of certain tree species (due to selective logging) may have cascade effects in the community. Furthermore, the lack of phylogenetic correspondence suggests that tree-moss associations are governed by ecological factors (host tree preferences). Moss-hummingbird associations are non-random, as hummingbirds (that pollinate these trees) are actively selecting mosses for nest building, stressing the importance of cryptic interactions as a community-structuring process. A freePlain Language Summarycan be found within the Supporting Information of this article.
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| 7. |
- van den Elzen, Eva, et al.
(author)
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Variation in symbiotic N-2 fixation rates among Sphagnum mosses
- 2020
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In: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 15:2
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Journal article (peer-reviewed)abstract
- Biological nitrogen (N) fixation is an important process supporting primary production in ecosystems, especially in those where N availability is limiting growth, such as peatlands and boreal forests. In many peatlands, peat mosses (genus Sphagnum) are the prime ecosystem engineers, and like feather mosses in boreal forests, they are associated with a diverse community of diazotrophs (N-2-fixing microorganisms) that live in and on their tissue. The large variation in N-2 fixation rates reported in literature remains, however, to be explained. To assess the potential roles of habitat (including nutrient concentration) and species traits (in particular litter decomposability and photosynthetic capacity) on the variability in N-2 fixation rates, we compared rates associated with various Sphagnum moss species in a bog, the surrounding forest and a fen in Sweden. We found appreciable variation in N-2 fixation rates among moss species and habitats, and showed that both species and habitat conditions strongly influenced N-2 fixation. We here show that higher decomposition rates, as explained by lower levels of decomposition-inhibiting compounds, and higher phosphorous (P) levels, are related with higher diazotrophic activity. Combining our findings with those of other studies, we propose a conceptual model in which both species-specific traits of mosses (as related to the trade-off between rapid photosynthesis and resistance to decomposition) and P availability, explain N-2 fixation rates. This is expected to result in a tight coupling between P and N cycling in peatlands.
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| 8. |
- Yusup, Shuayib, et al.
(author)
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Smoke promotes germination of peatland bryophyte spores
- 2023
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In: Journal of Experimental Botany. - : Oxford University Press. - 0022-0957 .- 1460-2431. ; 74:1, s. 251-264
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Journal article (peer-reviewed)abstract
- Northern peatlands are globally important carbon stores. With increasing fire frequency, the re-establishment of bryophytes becomes crucial for their carbon sequestration. Smoke-responsive germination is a common trait of seeds in fire-prone ecosystems but has not been demonstrated in bryophytes. To investigate the potential role of smoke in post-fire peatland recovery, we tested the germination of spores of 15 bryophyte species after treatment with smoke-water. The smoke responsiveness of spores with different laboratory storage times and burial depths/age (3-200 years) was subsequently tested. Smoke increased the germination percentage for 10 of the species and the germination speed for four of these. Smoke responsiveness increased along the fire frequency gradient from open expanse to forest margin, consistent with the theory that this selects for the maintenance of fire-adapted traits. Smoke enhanced the germinability of 1-year but not 4-year laboratory-stored spores, and considerably increased the germinability of spores naturally buried in peat for up to similar to 200 years. The effect of fire may be overlooked in non-fire-prone ecosystems, such as those in which wetland bryophytes dominate. Our study reveals a mechanism by which an increase in fire frequency may lead to shifts in species dominance, which may affect long-term carbon sequestration in peatlands.
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