| 1. |
- Bengtsson, Fia, 1986-
(författare)
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Functional Traits in Sphagnum
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 2. |
- Campbell, Charles, 1982-
(författare)
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Sphagnum limits : Physiology, morphology and climate
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sphagnum is the most important plant genus in terms of terrestrial carbon cycling. It and the habitats it creates store an equivalent of ~68% of the CO2 in the atmosphere. The genus has little dispersal limitation and the mire habitats are functionally similar at global scales. Sphagnum species are limited by water deficit at local and biogeographic scales, but this alone is not sufficient to explain local and global scale species patterns. As Sphagnum shoots are long-lived they may be limited by stochastic periods of cold temperature. Within Europe, species are associated with climate gradients along north-south (cold-warm) and oceanic-continental (wet-dry) clines. Within mires, species are sorted along a moisture (hummock-hollow) gradient.In this thesis I examined species responses to and recovery from freezing (I). I compared species with different water level niches in traits related to water management of individual shoots and colonies (II). Using distribution modelling of GBIF data, I estimated how different aspects of climate contributed to Sphagnum species distributions in Europe (III). Combining the approaches in papers II and III, I modelled the climatic distributions of the parapatric species S. cuspidatum and S. lindbergii and assessed how traits of water economy varied across the distribution boundary (IV).Species responses to winter stress were largely allied to both their hydrological niche and geographic range. Generally, hollow species managed better than hummock species, but species from intermediate positions were less consistent in their response. Species associated with boreal regions were generally less affected than those from temperate regions. Hardening against low temperature was triggered by shorter days and cold nights. Cold temperatures during late autumn may be more important for Sphagnum limits than the minimum temperature during winter.Water-related traits split the species into two groups; hollows species with large capitula and hummock species with small capitula. However, inter- and intra-specific trait variation and trait trends along the hydrological gradient were not necessarily the same at the shoot and canopy scale. Some trait correlations were common to all species. Canopy traits, which were emergent traits of colonies of shoots, had the strongest trait associations with the species position along the hummock-hollow gradient.At the continental scale the distribution of most Sphagnum species could be successfully modelled by a combination of annual degree days and water balance and the degree of seasonality in these two variables. Individual species distributions were shaped more by the seasonality in degree days than in water balance.Across the distributional border of S. cuspidatum and S. lindbergii divergence in the measured traits was mostly seen in the capitula indicating that limits to Sphagnum species are strongly linked to the functioning of the capitulum. Capitulum mass of both species was lower in sympatry than in allopatry, even though the measured values were similar. Canopy traits most strongly separated the species though did not change across the species boundaries.In summary, Sphagnum species in general are limited by the availability of water. Low temperature, particularly during late autumn are probably decisive for the biogeographic limits and for the distribution of species along the hydrological gradient.
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| 3. |
- Granath, Gustaf
(författare)
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Assessment of an integrated peat-harvesting and reclamation method: peatland-atmosphere carbon fluxes and vegetation recovery
- 2015
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Ingår i: Wetlands Ecology and Management. - : Springer Science and Business Media LLC. - 0923-4861 .- 1572-9834. ; 23, s. 491-504
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Tidskriftsartikel (refereegranskat)abstract
- We document a two-year experimental trial of a recently-developed integrated peat-harvesting and reclamation technique at a poor fen in northern Ontario, Canada. We removed and conserved the uppermost similar to 0.3 m of peat in blocks while deeper peat was harvested from the resultant pit. We allowed the extraction pit to flood with shallow groundwater, and then reclaimed the conserved surficial peat blocks by transplanting them into the flooded pit where they formed a low, floating mat. In the 2nd year after harvest average Sphagnum cover in our experimental plot was intermediate (similar to 25 %) between hummocks (similar to 100 %) and hollows (similar to 10 %) at an adjacent unharvested reference plot. Mean rates of Sphagnum productivity were greater in the experimental plot (65-86 g m(-2) month(-1)) than in the reference plot (45-55 g m(-2) month(-1)) for both hummock (S. fuscum) and lawn (S. magellanicum) species, although not significantly so, indicating that the transplant had no adverse effects on Sphagnum health. The inundated soil conditions in the trial pit prevented the large carbon dioxide emissions that are characteristic of many harvested peatlands. During the second growing season midday net ecosystem exchange at the experimental plot was similar to that at hollows in the reference plot. However, the anoxic soil conditions in the experimental plot led to highly elevated methane emissions in both years. Our results demonstrate that the method can enable rapid re-establishment of a healthy Sphagnum mat and carbon dioxide sequestration function in harvested peatlands, although the global warming potential of our experimental trial was high due to elevated methane emissions.
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| 4. |
- Granath, Gustaf
(författare)
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Effect of temperature and precipitation on linear increment of Sphagnum fuscum and S-magellanicum in Western Siberia
- 2017
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Ingår i: Russian Journal of Ecology. - 1067-4136 .- 1608-3334. ; 48, s. 203-211
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Tidskriftsartikel (refereegranskat)abstract
- The linear increment of Sphagnum fuscum and S. magellanicum in ombrotrophic mires of Western Siberia has been measured during two years over a transect about 2500 km long extending from forest-steppe to forest-tundra. Along the latitudinal gradient, the increment of both species has proved to be correlated with annual average air temperature and, in S. magellanicum, also with annual precipitation. The determinants of their growth differ between the southern, central, and northern parts of the study region. At the regional level, the annual and summer precipitation plays a more important role than the average air temperature. The increment of S. fuscum in the southern part is positively correlated with the amount of precipitation and negatively correlated with summer temperature, whereas the situation in the central part is inverse. In S. magellanicum, the linear increment is directly dependent on the annual average temperature and annual and summer precipitation in the south and on the annual and summer precipitation in the north of Western Siberia. The dynamics of linear growth of both species in bog pine forests during the growing season are similar: its rate is the highest in June, when the linear increment of S. fuscum and S. magellanicum amounts to 60 and 85% of the annual total, respectively.
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| 5. |
- Granath, Gustaf, et al.
(författare)
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Environmental and taxonomic controls of carbon and oxygen stable isotope composition in Sphagnum across broad climatic and geographic ranges
- 2018
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Ingår i: Biogeosciences. - : Copernicus Publications. - 1726-4170 .- 1726-4189. ; 15:16, s. 5189-5202
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Granath, Gustaf, et al.
(författare)
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Evolution of niche preference in Sphagnum peat mosses
- 2015
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 69:1, s. 90-103
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Tidskriftsartikel (refereegranskat)abstract
- Peat mosses (Sphagnum) are ecosystem engineersspecies in boreal peatlands simultaneously create and inhabit narrow habitat preferences along two microhabitat gradients: an ionic gradient and a hydrological hummock-hollow gradient. In this article, we demonstrate the connections between microhabitat preference and phylogeny in Sphagnum. Using a dataset of 39 species of Sphagnum, with an 18-locus DNA alignment and an ecological dataset encompassing three large published studies, we tested for phylogenetic signal and within-genus changes in evolutionary rate of eight niche descriptors and two multivariate niche gradients. We find little to no evidence for phylogenetic signal in most component descriptors of the ionic gradient, but interspecific variation along the hummock-hollow gradient shows considerable phylogenetic signal. We find support for a change in the rate of niche evolution within the genusthe hummock-forming subgenus Acutifolia has evolved along the multivariate hummock-hollow gradient faster than the hollow-inhabiting subgenus Cuspidata. Because peat mosses themselves create some of the ecological gradients constituting their own habitats, the classic microtopography of Sphagnum-dominated peatlands is maintained by evolutionary constraints and the biological properties of related Sphagnum species. The patterns of phylogenetic signal observed here will instruct future study on the role of functional traits in peatland growth and reconstruction.
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| 7. |
- Granath, Gustaf
(författare)
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Hydrological feedbacks in northern peatlands
- 2015
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Ingår i: Ecohydrology. - : Wiley. - 1936-0584 .- 1936-0592. ; 8, s. 113-127
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Tidskriftsartikel (refereegranskat)abstract
- Northern peatlands provide important global and regional ecosystem services (carbon storage, water storage, and biodiversity). However, these ecosystems face increases in the severity, areal extent and frequency of climate-mediated (e.g. wildfire and drought) and land-use change (e.g. drainage, flooding and mining) disturbances that are placing the future security of these critical ecosystem services in doubt. Here, we provide the first detailed synthesis of autogenic hydrological feedbacks that operate within northern peatlands to regulate their response to changes in seasonal water deficit and varying disturbances. We review, synthesize and critique the current process-based understanding and qualitatively assess the relative strengths of these feedbacks for different peatland types within different climate regions. We suggest that understanding the role of hydrological feedbacks in regulating changes in precipitation and temperature are essential for understanding the resistance, resilience and vulnerability of northern peatlands to a changing climate. Finally, we propose that these hydrological feedbacks also represent the foundation of developing an ecohydrological understanding of coupled hydrological, biogeochemical and ecological feedbacks. Copyright (c) 2014 John Wiley & Sons, Ltd.
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| 8. |
- Granath, Gustaf
(författare)
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Mitigating wildfire carbon loss in managed northern peatlands through restoration
- 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
- Northern peatlands can emit large amounts of carbon and harmful smoke pollution during a wildfire. Of particular concern are drained and mined peatlands, where management practices destabilize an array of ecohydrological feedbacks, moss traits and peat properties that moderate water and carbon losses in natural peatlands. Our results demonstrate that drained and mined peatlands in Canada and northern Europe can experience catastrophic deep burns (>200 t C ha(-1) emitted) under current weather conditions. Furthermore, climate change will cause greater water losses in these peatlands and subject even deeper peat layers to wildfire combustion. However, the rewetting of drained peatlands and the restoration of mined peatlands can effectively lower the risk of these deep burns, especially if a new peat moss layer successfully establishes and raises peat moisture content. We argue that restoration efforts are a necessary measure to mitigate the risk of carbon loss in managed peatlands under climate change.
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| 9. |
- Granath, Gustaf, et al.
(författare)
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Nitrogen fertilization reduces wild berry production in boreal forests
- 2017
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 390, s. 119-126
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen is the main limiting nutrient in temperate and boreal forests. Large-scale nitrogen fertilization has been suggested as a potential tool to enhance production and meet the increasing demand for wood products and biofuels. Here, we test the effect of N fertilization and thinning on berry (i.e., fruit) production and incidence of fungal pathogens along a latitudinal gradient in Sweden. We used an N fertilization (100-150 kg ha(-1)) and thinning experiment that was established between 1970 and 1980 in 30 pine forests, covering a latitudinal gradient stretching from southern to northern Sweden. We measured fruit production and disease incidence of fungal pathogens in bilberry and cowberry in the experimental plots (30 x 30 m), over two years (2014 and 2015), when the stands were between 67 and 85 years old. Nitrogen fertilization reduced fruit production for both species, while thinning had a positive effect. For cowberry, treatment effects on fruit production were mainly associated with changes in plant cover, while direct treatment effects altered fruit production in bilberry. Furthermore, N application increased disease incidence of the parasitic fungus Valdensia heterodoxa in bilberry and contributed to the reduced fruit production in the N treatment. In contrast, disease incidence of the main parasitic fungus in cow berry (snow-mold disease) was negatively affected by N. Thinning decreased disease incidence in bilberry, but tended to increase incidence in cowberry. For cowberry, disease incidence increased with latitude. Overall, our results suggest that the N-induced effect on fruit production in bilberry is partly associated with presence of the parasitic fungus, and largely due to unknown direct effects. For cowberry, reduction in fruit production is correlated with N-induced negative effects on plant cover. Large-scale fertilization will have an overall negative impact on fruit production, and given that fruit production is considered highly valuable in the context of ecosystem services and functioning, this reduction should be considered when forest management scenarios that include N fertilization are evaluated. Thinning on the other hand, can promote fruit production and may be used as a management tool to generate berry-rich forests. ( C) 2017 Elsevier B.V. All rights reserved.
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| 10. |
- Granath, Gustaf
(författare)
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Peatland bryophyte responses to increased light from black spruce removal
- 2017
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Ingår i: Ecohydrology. - : Wiley. - 1936-0584 .- 1936-0592. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- The ecohydrological impact of tree-canopy removal on moss and peat, which provide a principal carbon store, is just starting to be understood. Different mosses have contrasting contributions to carbon and water fluxes (e.g., Sphagnum fuscum, Pleurozium schreberi) and are strongly influenced by tree-canopy cover. Changes in tree-canopy cover may therefore lead to long-term shifts in species composition and associated ecohydrological function. However, the medium-term response to such disturbance, the associated lag in this transition to a new ecohydrological and biogeochemical regime, is not understood in detail. We investigate this medium-term (4years) ecohydrological, biogeochemical, and species compositional response to tree-canopy removal using a randomized plot design within a northern peatland. This is the only study to test for the influence of increased light alone. We demonstrate that changes in treatment plots 4years after tree-canopy removal were not significant. Notably, P.schreberi and S.fuscum remained within their respective plots post treatment, and there was no significant difference in plot resistance to evapotranspiration or carbon exchange. Results show that tree-canopy removal alone has little impact on bryophyte ecohydrology in the short or medium-term. This resistance to disturbance contrasts strongly with short-term changes observed within mineral soils, suggesting that concurrent shifts in the large scale hydrology induced within such disturbances are necessary to cause rapid ecohydrological transitions. Understanding this lagged response is critical to determine the strength of medium to long-term negative ecohydrological feedbacks within peatlands in addition to carbon and water fluxes on a decadal timescale in response to disturbance.
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