Plant polyphenols – implications of different sampling, storage and sample processing in biodiversity-ecosystem functioning experiments

Abstract

Plant polyphenols are involved in important ecosystem processes and may affect nutrient cycling. Previous investigations have demonstrated detrimental effects of suboptimal sample treatment on the quantity of extractable plant polyphenols. We compared leaf polyphenol concentrations of 20 tree species from East China in two sample sets collected under different conditions: (a) according to established protocols and stored more than three years, (b) under conditions optimised for leaf polyphenols. We investigated the variance brought about by suboptimal sample handling as compared to the variance caused by the taxonomic range of species. Family-affiliation explained the largest proportion of variance, whereas sample handling had only minor effects. Reducing the taxonomic range increased the impact of differences in sample handling. Additionally, we showed that the concentrations of leaf polyphenols were phylogenetically more conserved than other leaf traits. Non-metric-multi-dimensional scaling revealed similar ordination patterns for leaf polyphenol concentrations in both sample sets with both ordinations being closely correlated. Finally, we computed separate ordinations including an extended set of leaf traits and found that both analyses led to similar ecological conclusions. Consequently, in studies comprising a wide taxonomic range, the adverse effects of suboptimal sample handling may be overridden by the variation brought about by phylogeny.

Keywords:

• phylogenetic trait conservatism
• plant functional traits
• plant polyphenols
• procrustes analysis
• sampling conditions
• variance components analysis

Acknowledgements

We are grateful to M. Böhnke and A. Hallensleben for their relentless field and lab work on the investigated species traits and thank the whole BEF-China team for the inspiring working atmosphere. O. Purschke provided the species phylogeny and assistance with the phylogenetic analyses.

Funding

This work was financed by the DFG [FOR891/2] to H.B. [BR1698/9–2] and by a grant by the Sino-German Centre for Research Promotion in Beijing for a summer school in Gutianshan [GZ 698].