Biochemical determinants of litter quality in 15 species of Sphagnum

Abstract

Background and aims Sphagnum mosses are ecosystem engineers that create and maintain boreal peatlands. With unique biochemistry, waterlogging and acidifying capacities, they build up meters-thick layers of peat, reducing competition and impeding decomposition. We quantify within-genus differences in biochemical composition to make inferences about decay rates, related to hummock-hollow and fen-bog gradients and to phylogeny. Methods We sampled litter from 15 Sphagnum species, abundant over the whole northern hemisphere. We used regression and Principal Components Analysis (PCA) to evaluate general relationships between litter quality parameters and decay rates measured under laboratory and field conditions. Results Both concentrations of the polysaccharide sphagnan and the soluble phenolics were positively correlated with intrinsic decay resistance, however, so were the previously understudied lignin-like phenolics. More resistant litter had more of all the important metabolites; consequently, PC1 scores were related to lab mass loss (R 2 = 0.57). There was no such relationship with field mass loss, which is also affected by the environment. PCA also revealed that metabolites clearly group Sphagnum sections (subgenera). Conclusions We suggest that the commonly stated growth-decomposition trade-off is largely due to litter quality. We show a strong phylogenetic control on Sphagnum metabolites, but their effects on decay are affected by nutrient availability in the habitat.

Untargeted metabolomic profiling ofSphagnum fallaxreveals novel antimicrobial metabolites

“…Yet of all the compounds detected, our data only classified two compounds as phenols, 2‐{Bis[(4‐phenyl‐1,3‐thiazol‐2‐yl)amino]methyl}phenol and 4‐tert‐Octylphenol monoethoxylate, detected in LC‐MS negative mode (Table ), and one quinone detected via 1 H NMR at a concentration of 8.4 µM (Table ). While these three could be the players in antimicrobial properties, it is likely these are not fully responsible for decomposer suppression, which corresponds with previous research (Bengtsson et al, ; Mellegård et al, ).…”

“…The ambiguity in compounds and related function of various Sphagnum compounds on ecosystem variables elucidates an important research gap to gauge how these mosses control their ecosystems. Furthermore, this gap is widened by limitations in testing methodology, where previous studies have used singular analytical techniques which cannot identify a full suite of compounds (i.e., gas chromatography‐mass spectrometry, pyrolysis molecular beam mass spectrometry, 13 C NMR; Black, Cornhill, & Woodward, ; Limpens, Bohlin, & Nilsson, ; Turetsky et al, ; Verhoeven & Liefveld, ), have focused only on specific compounds or classes of compounds (Ballance, Børsheim, Inngjerdingen, Paulsen, & Christensen, ; Klavina, Springe, Steinberga, Mezaka, & Ievinsh, ), or have concentrated on applied function rather than identifying structures (Bengtsson, Granath, & Rydin, ; Bengtsson, Rydin, & Hájek, ; Hájek et al, ). While all of these are crucial to understanding Sphagnum and its ecosystem roles, a full‐suite chemical characterization of Sphagnum fallax metabolites is currently missing from the literature.…”

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

“…Data on environmental gradients (water level and shade), functional traits (architectural and physiological), and ecosystem processes (production and decomposition) for 15 Sphagnum species have been collected from the three study sites in the boreonemoral zone by Bengtsson, Granath, and Rydin (, ), Bengtsson, Rydin, and Hájek (), Laing et al () and Laing, Granath, Belyea, Allton, and Rydin () (Supporting Information Appendix ; refer to Table for explanations of abbreviations and units). We refer to this literature for further information about the procedures for measuring environmental variables and trait estimation.…”

“…The model was built by making use of the field and laboratory measurements of environmental variables, traits, and emerging ecosystem processes from the two datasets presented above and analysed in Bengtsson et al (, ), Bengtsson et al (), Laing et al () and Laing et al () (Tables and ). Similar methodologies of measurement were applied in both datasets (see the specific paragraph).…”

“…The full piecewise SEM path analysis (system of linear equations) includes the main categories of mechanistic relationship detailed in the paragraph Modeling the Mechanistic Pathway for Sphagnum. Each relationship derives from former field and laboratory experiments (Bengtsson et al, ; Granath et al, ; Hayward & Clymo, ; Laing et al, 2014a; Rice et al, ). The categories of mechanistic relationships are represented in Figure a.…”