Scaling functional traits to ecosystem processes: Towards a mechanistic understanding in peat mosses


1. 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 subse -quently 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 pro -cesses across levels of biological organization.
2. We gathered data on functional traits for 15 globally important Sphagnum speciescovering a wide range of ecological preferences. Phenotypes lie along well -estab -lished axes of the plant economic spectrum characterizing trade -offs between vital physiological functions. Using SEM, we clarified the mechanisms of trait co-variation 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 re -source conservation, via slow traits and processes.
3. We parameterized a process-based model estimating ecosystem processes linking environmental drivers with architectural and functional traits. In our SEM ap -proach the amount of variance explained varied substantially (0.29 ≤ R2 ≤ 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. R2 variabilitywas mainly explained by traits and species identity, and poorly by environmental filtering.
4. Some Sphagnum species avoid the stress caused by periodic desiccation in hollowsvia 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.
5. Synthesis. We contribute to a unified theory generating individual fitness, canopydynamics and ecosystem processes from trait variation. As for vascular plants, 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.


Link to centre authors: Norberg, Jon
Full reference: Mazziotta, A., Granath, G., Rydin, H., Bengtsson, F. and Norberg, J., 2018. Scaling functional traits to ecosystem processes: towards a mechanistic understanding in peat mosses. Journal of Ecology.