| 1. |
- Bengtsson, Fia, 1986-, et al.
(author)
-
Environmental drivers of Sphagnum growth in peatlands across the Holarctic region
- 2021
-
In: Journal of Ecology. - : John Wiley & Sons. - 0022-0477 .- 1365-2745. ; 109:1, s. 417-431
-
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.
|
|
| 2. |
- Bengtsson, Fia, 1986-
(author)
-
Functional Traits in Sphagnum
- 2019
-
Doctoral thesis (other academic/artistic)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.
|
|
| 3. |
- Mazziotta, Adriano, et al.
(author)
-
Scaling functional traits to ecosystem processes : Towards a mechanistic understanding in peat mosses
- 2019
-
In: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 107:2, s. 843-859
-
Journal article (peer-reviewed)abstract
- 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.
|
|
| 4. |
- van den Elzen, Eva, et al.
(author)
-
Variation in symbiotic N-2 fixation rates among Sphagnum mosses
- 2020
-
In: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 15:2
-
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.
|
|
