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Bengtsson, F. (2019). Functional Traits in Sphagnum. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Functional Traits in Sphagnum
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Peat mosses (Sphagnum) are ecosystem engineers that largely govern carbon sequestration in northern hemisphere peatlands. I investigated functional traits in Sphagnum species and addressed the questions: (I) Are growth, photosynthesis and decomposition and the trade-offs between these traits related to habitat or phylogeny?, (II) Which are the determinants of decomposition and are there trade-offs between metabolites that affect decomposition?, (III) How do macro-climate and local environment determine growth in Sphagnum across the Holarctic?, (IV) How does N2 fixation vary among different species and habitats?, (V) How do species from different microtopographic niches avoid or tolerate desiccation, and are leaf and structural traits adaptations to growth high above the water table?

Photosynthetic rate and decomposition in laboratory conditions (innate growth and decay resistance) were related to growth and decomposition in their natural habitats. We found support for a trade-off between growth and decay resistance, but innate qualities translated differently to field responses in different species. There were no trade-offs between production of different decay-affecting metabolites. Their production is phylogenetically controlled, but their effects on decay are modified by nutrient availability in the habitat. Modelling growth of two species across the Holarctic realm showed that precipitation, temperature and vascular plant cover are the best predictors of performance, but responses were stronger for the wetter growing species. N2 fixation rates were positively related to moss decomposability, field decomposition and tissue phosphorus concentration. Hence, higher decomposition can lead to more nutrients available to N2-fixing microorganisms, while higher concentrations of decomposition-hampering metabolites may impede N2 fixation. A mesocosm experiment, testing effects of water level drawdown on water content and chlorophyll fluorescence, showed that either slow water loss or high maximum water holding capacity can lead to desiccation avoidance. Furthermore, leaf anatomical traits rather than structural traits affected the water economy.

This thesis has advanced the emerging field of trait ecology in Sphagnum by comparing many species and revealing novel mechanisms and an ever more complex picture of Sphagnum ecology. In addition, the species-specific trait measurements of this work offers opportunities for improvements of peatland ecosystem models.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 45
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1771
Keywords
peat mosses, functional traits, NPP, decay resistance, N2 fixation, desiccation resistance, climate
National Category
Ecology
Research subject
Biology with specialization in Ecological Botany
Identifiers
urn:nbn:se:uu:diva-375011 (URN)978-91-513-0568-4 (ISBN)
Public defence
2019-03-15, Zootissalen, EBC, Villavägen 9, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2019-02-21 Created: 2019-01-25 Last updated: 2019-03-18
Mazziotta, A., Granath, G., Rydin, H., Bengtsson, F. & Norberg, J. (2019). Scaling functional traits to ecosystem processes: Towards a mechanistic understanding in peat mosses. Journal of Ecology, 107(2), 843-859
Open this publication in new window or tab >>Scaling functional traits to ecosystem processes: Towards a mechanistic understanding in peat mosses
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2019 (English)In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 107, no 2, p. 843-859Article in journal (Refereed) Published
Abstract [en]

The role of trait trade-offs and environmental filtering in explaining the variability in functional traits and ecosystem processes has received considerable attention for vascular plants but less so for bryophytes. Thus, we do not know whether the same forces also shape the phenotypic variability of bryophytes. Here, we assess how environmental gradients and trade-offs shape functional traits and subsequently ecosystem processes for peat mosses (Sphagnum), a globally important plant genus for carbon accumulation. We used piecewise Structural Equation Modeling (SEM) to understand how environmental gradients influence vital processes across levels of biological organization. We gathered data on functional traits for 15 globally important Sphagnum species covering a wide range of ecological preferences. Phenotypes lie along well-established axes of the plant economic spectrum characterizing trade-offs between vital physiological functions. Using SEM, we clarified the mechanisms of trait covariation and scaling to ecosystem processes. We tested whether peat mosses, like vascular plants, constrain trait variability between a fast turnover strategy based on resource acquisition via fast traits and processes, and a strategy of resource conservation, via slow traits and processes. We parameterized a process-based model estimating ecosystem processes linking environmental drivers with architectural and functional traits. In our SEM approach the amount of variance explained varied substantially (0.29 <= R-2 <= 0.82) among traits and processes in Sphagnum, and the model could predict some of them with high to intermediate accuracy for an independent dataset. R-2 variability was mainly explained by traits and species identity, and poorly by environmental filtering. Some Sphagnum species avoid the stress caused by periodic desiccation in hollows via resource acquisition based on fast photosynthesis and growth, while other species are adapted to grow high above the water-table on hummocks by slow physiological traits and processes to conserve resources. Synthesis.We contribute to a unified theory generating individual fitness, canopy dynamics and ecosystem processes from trait variation. As for vascular plants, the functional traits in the Sphagnum economic spectrum are linked into an integrated phenotypic network partly filtered by the environment and shaped by trade-offs in resource acquisition and conservation.

Place, publisher, year, edition, pages
WILEY, 2019
Keywords
bryophytes, ecosystem processes, peatlands, piecewise SEM, plant development and life-history traits, plant economic spectrum, Sphagnum, Structural Equation Modeling
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-378633 (URN)10.1111/1365-2745.13110 (DOI)000458616400029 ()
Funder
Swedish Research Council
Available from: 2019-03-07 Created: 2019-03-07 Last updated: 2019-03-07Bibliographically approved
Bengtsson, F., Rydin, H. & Hajek, T. (2018). Biochemical determinants of litter quality in 15 species of Sphagnum. Plant and Soil, 425(1-2), 161-176
Open this publication in new window or tab >>Biochemical determinants of litter quality in 15 species of Sphagnum
2018 (English)In: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 425, no 1-2, p. 161-176Article in journal (Refereed) Published
Abstract [en]

Background and aims Sphagnum mosses are ecosystem engineers that create and maintain boreal peatlands. With unique biochemistry, waterlogging and acidifying capacities, they build up meters-thick layers of peat, reducing competition and impeding decomposition. We quantify within-genus differences in biochemical composition to make inferences about decay rates, related to hummock-hollow and fen-bog gradients and to phylogeny. Methods We sampled litter from 15 Sphagnum species, abundant over the whole northern hemisphere. We used regression and Principal Components Analysis (PCA) to evaluate general relationships between litter quality parameters and decay rates measured under laboratory and field conditions. Results Both concentrations of the polysaccharide sphagnan and the soluble phenolics were positively correlated with intrinsic decay resistance, however, so were the previously understudied lignin-like phenolics. More resistant litter had more of all the important metabolites; consequently, PC1 scores were related to lab mass loss (R-2 = 0.57). There was no such relationship with field mass loss, which is also affected by the environment. PCA also revealed that metabolites clearly group Sphagnum sections (subgenera). Conclusions We suggest that the commonly stated growth-decomposition trade-off is largely due to litter quality. We show a strong phylogenetic control on Sphagnum metabolites, but their effects on decay are affected by nutrient availability in the habitat.

Keywords
Peatland, Decay resistance, Sphagnan, Phenolics, Lignin, Hummock-hollow
National Category
Botany
Identifiers
urn:nbn:se:uu:diva-354249 (URN)10.1007/s11104-018-3579-8 (DOI)000430992300011 ()
Funder
Swedish Research CouncilThe Royal Swedish Academy of Sciences
Note

Correction in: PLANT AND SOIL, Volume: 439, Issue: 1-2, Pages: 569-572, Special Issue: SI, DOI: 10.1007/s11104-019-04046-5

Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2019-08-16Bibliographically approved
Tyler, T., Bengtsson, F., Dahlberg, C. J., Lonnell, N., Hallingback, T. & Reitalu, T. (2018). Determinants of bryophyte species composition and diversity on the Great Alvar of oland, Sweden. Journal of Bryology, 40(1), 12-30
Open this publication in new window or tab >>Determinants of bryophyte species composition and diversity on the Great Alvar of oland, Sweden
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2018 (English)In: Journal of Bryology, ISSN 0373-6687, E-ISSN 1743-2820, Vol. 40, no 1, p. 12-30Article in journal (Refereed) Published
Abstract [en]

Factors driving the species richness and distribution of bryophytes are poorly studied and not well understood, particularly in grasslands. We analysed the occurrence of bryophyte species and variation in species richness across 674 plots (0.5 m x 0.5 m) in alvar vegetation (grassland on limestone pavement with thin or no soil) on oland (Sweden) in relation to substrate characteristics and chemistry, inundation frequency, grazing pressure and geographical variables. We found 148 taxa, including 11 nationally red-listed ones. Species richness per plot was significantly associated with substrate type, positively associated with pH and grazing intensity, but negatively associated with soil depth. However, richness of species typical of, or restricted to, alvar habitats responded differently to richness of species more common in other habitats. Typical alvar species were favoured by high pH, shallow soil and low phosphate availability, while generalists preferred relatively low pH, higher phosphate availability and organic or mull soil types. Distance from the alvar margin had only weak effects. Concerning the effects on individual species and community composition, inundation frequency and pH were found to have the largest effects, although other factors (substrate type, soil depth, bare soil, bare stone, phosphate availability and grazing pressure) were more important for some individual species, stressing the importance of microsite variability and variability in management for regional species richness. From a conservation perspective, it is concluded that grazing is generally positive whilst factors increasing phosphate availability may disadvantage the typical alvar species, and proximity to the alvar margin is not a major problem.

Place, publisher, year, edition, pages
TAYLOR & FRANCIS LTD, 2018
Keywords
Alvar, Calcareous grassland, Edge effect, Grazing, Inundation, pH, Phosphate, Soil chemistry, Soil depth, Species richness
National Category
Ecology Botany
Identifiers
urn:nbn:se:uu:diva-358578 (URN)10.1080/03736687.2017.1412387 (DOI)000435012200002 ()
Available from: 2018-09-17 Created: 2018-09-17 Last updated: 2018-09-17Bibliographically approved
Granath, G., Rydin, H., Baltzer, J. L., Bengtsson, F., Boncek, N., Bragazza, L., . . . Rice, S. K. (2018). Environmental and taxonomic controls of carbon and oxygen stable isotope composition in Sphagnum across broad climatic and geographic ranges. Biogeosciences, 15(16), 5189-5202
Open this publication in new window or tab >>Environmental and taxonomic controls of carbon and oxygen stable isotope composition in Sphagnum across broad climatic and geographic ranges
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2018 (English)In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, no 16, p. 5189-5202Article in journal (Refereed) Published
Abstract [en]

Rain-fed peatlands are dominated by peat mosses (Sphagnum sp.), which for their growth depend on nutrients, water and CO2 uptake from the atmosphere. As the isotopic composition of carbon (C-12(,)13) and oxygen (O-16(,)18) of these Sphagnum mosses are affected by environmental conditions, Sphagnum tissue accumulated in peat constitutes a potential long-term archive that can be used for climate reconstruction. However, there is inadequate understanding of how isotope values are influenced by environmental conditions, which restricts their current use as environmental and palaeoenvironmental indicators. Here we tested (i) to what extent C and O isotopic variation in living tissue of Sphagnum is speciesspecific and associated with local hydrological gradients, climatic gradients (evapotranspiration, temperature, precipitation) and elevation; (ii) whether the C isotopic signature can be a proxy for net primary productivity (NPP) of Sphagnum; and (iii) to what extent Sphagnum tissue delta O-18 tracks the delta O-18 isotope signature of precipitation. In total, we analysed 337 samples from 93 sites across North America and Eurasia us ing two important peat-forming Sphagnum species (S. magellanicum, S. fuscum) common to the Holarctic realm. There were differences in delta C-13 values between species. For S. magellanicum delta C-13 decreased with increasing height above the water table (HWT, R-2 = 17 %) and was positively correlated to productivity (R-2 = 7 %). Together these two variables explained 46 % of the between-site variation in delta C-13 values. For S. fuscum, productivity was the only significant predictor of delta C-13 but had low explanatory power (total R-2 = 6 %). For delta O-18 values, approximately 90 % of the variation was found between sites. Globally modelled annual delta O-18 values in precipitation explained 69 % of the between-site variation in tissue delta O-18. S. magellanicum showed lower delta O-18 enrichment than S. fuscum (-0.83 %0 lower). Elevation and climatic variables were weak predictors of tissue delta O-18 values after controlling for delta O-18 values of the precipitation. To summarize, our study provides evidence for (a) good predictability of tissue delta O-18 values from modelled annual delta O-18 values in precipitation, and (b) the possibility of relating tissue delta C-13 values to HWT and NPP, but this appears to be species-dependent. These results suggest that isotope composition can be used on a large scale for climatic reconstructions but that such models should be species-specific.

National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:uu:diva-364191 (URN)10.5194/bg-15-5189-2018 (DOI)000443077000002 ()
Funder
Swedish Research Council, 2015-05174
Available from: 2018-10-30 Created: 2018-10-30 Last updated: 2019-02-01Bibliographically approved
Bengtsson, F., Granath, G. & Rydin, H. (2016). Photosynthesis, growth, and decay traits in Sphagnum – a multispecies comparison. Ecology and Evolution, 6(10), 3325-3341
Open this publication in new window or tab >>Photosynthesis, growth, and decay traits in Sphagnum – a multispecies comparison
2016 (English)In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 6, no 10, p. 3325-3341Article in journal (Refereed) Published
Abstract [en]

Peat mosses (Sphagnum) largely govern carbon sequestration in Northern Hemisphere peatlands. We investigated functional traits related to growth and decomposition in Sphagnum species. We tested the importance of environment and phylogeny in driving species traits and investigated trade-offs among them. We selected 15 globally important Sphagnum species, representing four sections (subgenera) and a range of peatland habitats. We measured rates of photosynthesis and decomposition in standard laboratory conditions as measures of innate growth and decay potential, and related this to realized growth, production, and decomposition in their natural habitats. In general, we found support for a trade-off between measures of growth and decomposition. However, the relationships are not strong, with r ranging between 0.24 and 0.45 for different measures of growth versus decomposition. Using photosynthetic rate to predict decomposition in standard conditions yielded R2 = 0.20. Habitat and section (phylogeny) affected the traits and the trade-offs. In a wet year, species from sections Cuspidata and Sphagnum had the highest production, but in a dry year, differences among species, sections, and habitats evened out. Cuspidata species in general produced easily decomposable litter, but their decay in the field was hampered, probably due to near-surface anoxia in their wet habitats. In a principal components analysis, PCA, photosynthetic capacity, production, and laboratory decomposition acted in the same direction. The species were imperfectly clustered according to vegetation type and phylogeny, so that some species clustered with others in the same section, whereas others clustered more clearly with others from similar vegetation types. Our study includes a wider range of species and habitats than previous trait analyses in Sphagnum and shows that while the previously described growth–decay trade-off exists, it is far from perfect. We therefore suggest that our species-specific trait measures offer opportunities for improvements of peatland ecosystem models. Innate qualities measured in laboratory conditions translate differently to field responses. Most dramatically, fast-growing species could only realize their potential in a wet year. The same species decompose fast in laboratory, but their decomposition was more retarded in the field than that of other species. These relationships are crucial for understanding the long-term dynamics of peatland communities.

National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-284287 (URN)10.1002/ece3.2119 (DOI)000376646700024 ()27103989 (PubMedID)
Funder
Swedish Research CouncilSwedish Research Council FormasThe Royal Swedish Academy of Sciences
Available from: 2016-04-16 Created: 2016-04-16 Last updated: 2019-02-01Bibliographically approved
Bengtsson, F., Rydin, H. & Granath, G.Environmental drivers of Sphagnum growth in mires across the Holarctic region.
Open this publication in new window or tab >>Environmental drivers of Sphagnum growth in mires across the Holarctic region
(English)Manuscript (preprint) (Other academic)
Keywords
climate, global change, NPP, peatlands, peat mosses, nitrogen deposition
National Category
Natural Sciences
Research subject
Biology with specialization in Ecological Botany; Biology with specialization in Ecological Botany
Identifiers
urn:nbn:se:uu:diva-375010 (URN)
Available from: 2019-01-24 Created: 2019-01-24 Last updated: 2019-02-01
Bengtsson, F., Granath, G., Cronberg, N. & Rydin, H.Mechanisms behind species-specific water economy responses to water level drawdown in peat mosses.
Open this publication in new window or tab >>Mechanisms behind species-specific water economy responses to water level drawdown in peat mosses
(English)Manuscript (preprint) (Other academic)
Keywords
peat mosses, water economy, capitulum water content, bulk density, hyaline cell, pore size, leaf anatomy
National Category
Natural Sciences
Research subject
Biology with specialization in Ecological Botany
Identifiers
urn:nbn:se:uu:diva-375009 (URN)
Available from: 2019-01-24 Created: 2019-01-24 Last updated: 2019-02-01
van den Elzen, E., Bengtsson, F., Fritz, C., Rydin, H. & Lamers, L. P. ..Variation in symbiotic N2 fixation among Sphagnum and feather mosses.
Open this publication in new window or tab >>Variation in symbiotic Nfixation among Sphagnum and feather mosses
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(English)Manuscript (preprint) (Other academic)
Keywords
diazotrophs, peat moss, bog, peatland, nitrogen, phosphorus, carbon, nutrient cycling, traits, boreal forest
National Category
Natural Sciences
Research subject
Biology with specialization in Ecological Botany
Identifiers
urn:nbn:se:uu:diva-375008 (URN)
Available from: 2019-01-24 Created: 2019-01-24 Last updated: 2019-02-01
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0497-8316

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