DOI: 10.5061/dryad.1720vg5
title: Data from: Scaling functional traits to ecosystem processes: towards a mechanistic understanding in peat mosses

description: 1. The role of trait trade-offs and environmental filtering in explaining
 the variability of 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. 2. 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. 3. 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 ≤ 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 variability was mainly explained
 by traits and species identity, and poorly by environmental filtering. 4.
 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.
 5. 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.
description: Standardized dataset of
 environmental gradients, functional traits and ecosystem
 processesAppendix S2 in
 JEcol-T2.csv. Table representing the standardized dataset of environmental
 gradients, functional traits and ecosystem processes used in the R code to
 build the Piecewise SEM. Abbreviations in
 Mazziotta_et_al_2018_READ_ME.csv.JEcol-T2.csvPiecewise SEM in R codeAppendix S3 in JEcol-A3.R. The Piecewise SEM in R code solving the mechanistic pathways for 15 Sphagnum species. Abbreviations in Mazziotta_et_al_2018_READ_ME.csvJEcol-A3.RBengtsson-Granath test datasetAppendix S5 in JEcol-T5.csv. Table representing the full raw dataset of environmental gradients, functional traits and ecosystem processes for the Bengtsson-Granath testing dataset used for the validation of the SEM. Variable names and units as in Mazziotta_et_al_2018_READ_ME.csv.JEcol-T5.csv