Foliar fungi of Betula pendula: impact of tree species mixtures and assessment methods

Diem Nguyen,Michelle Cleary,Julia Koricheva,Helge Bruelheide,Johanna Boberg,Lydia Hönig,Jan Stenlid

doi:10.1038/srep41801

Abstract

Foliar fungi of silver birch (Betula pendula) in an experimental Finnish forest were investigated across a gradient of tree species richness using molecular high-throughput sequencing and visual macroscopic assessment. We hypothesized that the molecular approach detects more fungal taxa than visual assessment, and that there is a relationship among the most common fungal taxa detected by both techniques. Furthermore, we hypothesized that the fungal community composition, diversity, and distribution patterns are affected by changes in tree diversity. Sequencing revealed greater diversity of fungi on birch leaves than the visual assessment method. One species showed a linear relationship between the methods. Species-specific variation in fungal community composition could be partially explained by tree diversity, though overall fungal diversity was not affected by tree diversity. Analysis of specific fungal taxa indicated tree diversity effects at the local neighbourhood scale, where the proportion of birch among neighbouring trees varied, but not at the plot scale. In conclusion, both methods may be used to determine tree diversity effects on the foliar fungal community. However, high-throughput sequencing provided higher resolution of the fungal community, while the visual macroscopic assessment detected functionally active fungal species.

Highlights

Several ecological processes that apply to fungal pathogens may explain tree species diversity effects on fungal diversity and composition
We investigated whether the two methods to study fungal communities would reveal similar patterns of tree diversity effects on foliar fungi
Fungal community of birch leaves as characterized by high-throughput sequencing

Summary

Introduction

Several ecological processes that apply to fungal pathogens may explain tree species diversity effects on fungal diversity and composition. Many species that may be present in or on the leaves make no observable signs or symptoms, or have a long latency period before fruiting becomes evident[27], and fail to be detected. Another problem is that the fungi may have not yet been described at all. Despite these limitations, Hantsch and colleagues utilized visual detection methods of fungal taxa on leaves and found no significant tree species richness effects on foliar fungal species richness and pathogen load[10]. Vegetation zones, warming, and host genotypes were found to influence fungal community composition, diversity, and function[31,32,33]

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Conclusion