Patterns in moss element concentrations in fens across species, habitats, and regions

The ionome and stoichiometry of fen mosses have not yet been studied in extensive data sets despite their potential to explain ecological behaviour of the species and to indicate nutrient limitation or oversupply. We analysed element concentrations (N, P, K, Ca, Mg, and Fe) in apical parts of dominant peat and brown mosses along the complete pH/calcium gradient in fens of three Central European regions (the Western Carpathians, the Bohemian Massif and, marginally, the West-Bohemian mineral springs). We obtained data from 143 localities for 56 species, with the most replicates for calcium-tolerant Sphagnum warnstorfii. Tissue element concentrations were to a great extent determined by species identity, except for magnesium, iron, and potassium (in the potassium-poor region). Water chemistry determined substantially species' magnesium, potassium (in the potassium-poor region), and partially also calcium concentrations. Calcium and potassium concentrations were generally most predictable by water chemistry, water table depth (WTD), and species identity, while concentrations of nitrogen, phosphorus, and especially iron were least predictable. Principal component analysis across the species showed the same two principal gradients in all regions. One reflected the ratios between iron and the other ions and the other the ratios between calcium + magnesium and other ions, sorting the species from calcicole (Scorpidium cossonii) to acidicole (Sphagnum fallax). Particular species differed strongly with respect to calcium concentration in both the biomass and the water, and median calcium concentration in a species coincided greatly with median concentration in the water. Tissue phosphorus, nitrogen, and potassium also differed significantly among the species, but analogous coincidences with the concentrations in water were not found. The results for iron and magnesium were inconsistent between the regions. Within particular species, correlations between biomass and water element concentrations were either positive or negative, but largely nonsignificant. The rare moss Hamatocaulis vernicosus had higher element concentrations (except for nitrogen) than would be predicted from water chemistry, resembling the pattern of R-strategy plants. In the Western Carpathians, calcium concentrations in S. warnstorfii decreased significantly with WTD, becoming stabilised at around 5 mg/g at WTD > 15 cm. The inter-regional differences in species element concentrations were usually explainable by different iron, magnesium, and potassium concentrations in water, with signs of phosphorus immobilisation by iron such as generally higher N:P ratios in the iron- and simultaneously phosphorus-richer region (Bohemian Massif). Because moss chemical composition combines the effects of species identity and various effects of the environment, caution is needed in any meta-analysis. (C) 2014 Geobotanisches Institut ETH, Stiftung Ruebel. Published by Elsevier GmbH. All rights reserved.