Herbivore and pathogen effects on tree growth are additive, but mediated by tree diversity and plant traits

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Herbivores and fungal pathogens are key drivers of plant community composition and functioning. The effects of herbivores and pathogens are mediated by the diversity and functional characteristics of their host plants. However, the combined effects of herbivory and pathogen damage, and their consequences for plant performance, have not yet been addressed in the context of biodiversity–ecosystem functioning research. We analyzed the relationships between herbivory, fungal pathogen damage and their effects on tree growth in a large-scale forest-biodiversity experiment. Moreover, we tested whether variation in leaf trait and climatic niche characteristics among tree species influenced these relationships. We found significant positive effects of herbivory on pathogen damage, and vice versa. These effects were attenuated by tree species richness—because herbivory increased and pathogen damage decreased with increasing richness—and were most pronounced for species with soft leaves and narrow climatic niches. However, herbivory and pathogens had contrasting, independent effects on tree growth, with pathogens decreasing and herbivory increasing growth. The positive herbivory effects indicate that trees might be able to (over-)compensate for local damage at the level of the whole tree. Nevertheless, we found a dependence of these effects on richness, leaf traits and climatic niche characteristics of the tree species. This could mean that the ability for compensation is influenced by both biodiversity loss and tree species identity—including effects of larger-scale climatic adaptations that have been rarely considered in this context. Our results suggest that herbivory and pathogens have additive but contrasting effects on tree growth. Considering effects of both herbivory and pathogens may thus help to better understand the net effects of damage on tree performance in communities differing in diversity. Moreover, our study shows how species richness and species characteristics (leaf traits and climatic niches) can modify tree growth responses to leaf damage under real-world conditions.

Original languageEnglish
JournalEcology and Evolution
Issue number18
Pages (from-to)7462-7474
Number of pages13
Publication statusPublished - 09.2017

Bibliographical note

Funding text

We thank Xuefei Yang, Chen Lin, Sabine Both, Keping Ma, and all members of the BEF-China consortium that coordinated and helped with the establishment and maintenance of the experiment. We are indebted to our many helpers that contributed to the leaf damage and tree growth measurements. We thank Bastien Castagneyrol and anonymous reviewers for helpful comments. We gratefully acknowledge funding by the German Research Foundation (DFG FOR 891/1, 891/2 and 891/3) and the Sino-German Centre for Research Promotion in Bei?ing (GZ 524, 592, 698, 699, 785, 970, and 1020). BEF-China is supported by the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig (DFG FZT 118).

    Research areas

  • Ecosystems Research - BEF-China, biodiversity and ecosystem functioning, climatic niche, functional traits, fungal pathogens, plant–herbivore interactions