Can tissue element concentration patterns at the individual species level indicate the factors underlying vegetation gradients in wetlands?

Abstract

Question: Do tissue element concentrations at the individual species level vary along major vegetation gradients in wetlands, and can they indicate environmental conditions? Location: West Carpathians. Methods: Total plant species composition was recorded in plots distributed along a poor to rich gradient within spring fens and along the gradient from fens to wet meadows. Eriophorum angustifolium (Cyperaceae) and three broadleaf dicotyledonous herb species were collected from the vegetation plots. Tissue N, P, K, Ca and Fe concentrations, N:P and N:K ratios of the species were determined. Each variable was correlated with the sample scores along the first two axes of the DCA ordination, which represented the two main vegetation gradients. Results: K and Ca concentrations in a particular species correlated well with the vegetation gradients, thus indicating changes in the element availability to the species. The trends were sometimes contradictory to known patterns at the community level, but the differences could be ecologically interpreted. Contrary to Ca and K, patterns in N, P and Fe concentration appeared to be more species-specific. E. angustifolium had a lower K and Ca concentration than the broadleaf herbs. Conclusions: Compared to community-level measurements, element concentrations in individual species correlated less with observed vegetation gradients. Trends found at the species level may indicate changes in ecological conditions affecting the species, although they need not correspond with trends found at the community level. We conclude that the species-level approach cannot substitute, but can advance, the community-level approach in searching for mechanisms underlying vegetation gradients within wetlands.