| 1. |
- 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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| 2. |
- Granath, Gustaf, et al.
(author)
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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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In: Biogeosciences. - : Copernicus Publications. - 1726-4170 .- 1726-4189. ; 15:16, s. 5189-5202
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Journal article (peer-reviewed)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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| 3. |
- Granath, Gustaf, et al.
(author)
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Evolution of niche preference in Sphagnum peat mosses
- 2015
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In: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 69:1, s. 90-103
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Journal article (peer-reviewed)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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