SP 14: Foliar fungal pathogens

The effect of tree species diversity on foliar fungal pathogens

Principal investigator(s):

Dr. Lydia Hönig (Martin Luther University of Halle-Wittenberg)

Phd candidate(s):

Contact adress:

Martin Luther University Halle-Wittenberg, Institute of Biology / Geobotany and Botanical Garden, Am Kirchtor 1, 06108 Halle (Saale), Germany

Summary

Foliar fungal pathogens affect ecosystem processes in forests through highly species specific effects of trees on growth and survival. Thus, fungal pathogens can contribute to maintain tree diversity. As host-specialized pathogenic organisms such as foliar fungal pathogens are both response to as well as an effect of tree diversity in forests, both can be disentangled with the experimental design of BEF-China.

Objectives

The subproject focuses on the following four main objectives, addressing tree diversity effects on plot and single tree level as well as under decreasing P sources:

(1) Tree species diversity decreases disease risk and pathogen load of pathogenic fungi on a particular host species because host species density and thus, fungal habitat availability, is diluted with increasing tree species diversity.
(2) Tree species diversity increases foliar fungal species diversity.
(3) The phylogenetic similarity of host species increases the phylogenetic similarity of foliar fungal communities on different tree species, as a consequence of the co-evolution of the pathogens with their hosts.
(4) The degree of herbivory leads to increased fungal pathogen load.
(5) Increasing pathogen load decreases the growth and the fitness of tree individuals and species.

I will address these hypotheses with different experimental set ups of the BEF-China project. On the one hand, I will quantify the pathogen load as percentage of leaf area infected by foliar fungal pathogens across all tree species in all plots of the Main Experiment. On the other hand, I will identify for a total of 16 selected tree species all fungus species that occur on leaves of a certain tree species and construct tree species-specific phylogenies and trophobiotic networks. Finally, in the new BEFmod experiment I will assess the effect of foliar fungal pathogens on plant performance as well as the effects of P fertilization, competition of the herb layer and herbivory on pathogen load.

Monochaetia dimorphospora at Castanopsis sclerophylla (left) and Sterile ascomycet at Quercus serrata (right)

Combining information from the two observational levels and the experimental approach of BEFmod will allow me to address one of the key questions in functional biodiversity research: how pathogens mediate plant species richness-growth relationships in response to herbivory and tree species loss with a focus on trophobiotic interactions.