title: Tree diversity and the role of non-host neighbour tree species in reducing fungal pathogen infestation.
abstract: The degree to which plant pathogen infestation occurs in a host plant is expected to be strongly influenced by the level of species diversity among neighbouring host and non-host plant species. Since pathogen infestation can negatively affect host plant performance, it can mediate the effects of local biodiversity on ecosystem functioning.We tested the effects of tree diversity and the proportion of neighbouring host and non-host species with respect to the foliar fungal pathogens ofTilia cordataandQuercus petraeain the Kreinitz tree diversity experiment in Germany. We hypothesized that fungal pathogen richness increases while infestation decreases with increasing local tree diversity. In addition, we tested whether fungal pathogen richness and infestation are dependent on the proportion of host plant species present or on the proportion of particular non-host neighbouring tree species.Leaves of the two target species were sampled across three consecutive years with visible foliar fungal pathogens on the leaf surface being identified macro- and microscopically. Effects of diversity among neighbouring trees were analysed: (i) for total fungal species richness and fungal infestation on host trees and (ii) for infestation by individual fungal species.We detected four and five fungal species onT. cordataandQ. petraea, respectively. High local tree diversity reduced (i) total fungal species richness and infestation ofT. cordataand fungal infestation ofQ. petraeaand (ii) infestation by three host-specialized fungal pathogen species. These effects were brought about by local tree diversity and were independent of host species proportion. In general, host species proportion had almost no effect on fungal species richness and infestation. Strong effects associated with the proportion of particular non-host neighbouring tree species on fungal species richness and infestation were, however, recorded.Synthesis. For the first time, we experimentally demonstrated that for two common forestry tree species, foliar fungal pathogen richness and infestation depend on local biodiversity. Thus, local tree diversity can have positive impacts on ecosystem functioning in managed forests by decreasing the level of fungal pathogen infestation.
authors.affiliation: Institute of Biology/Geobotany and Botanical Garden, Martin Luther University Halle Wittenberg Am Kirchtor 1, Halle (Saale), D-06108, Germany.
authors.forename: Lydia
authors.initials: L
authors.lastname: Hantsch
authors.affiliation: Institute of Biology/Geobotany and Botanical Garden, Martin Luther University Halle Wittenberg Am Kirchtor 1, Halle (Saale), D-06108, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Bien
authors.affiliation: Institute of Biology/Geobotany and Botanical Garden, Martin Luther University Halle Wittenberg Am Kirchtor 1, Halle (Saale), D-06108, Germany.
authors.forename: Stine
authors.initials: S
authors.lastname: Radatz
authors.affiliation: Institute of Biology/Geobotany and Botanical Garden, Martin Luther University Halle Wittenberg Am Kirchtor 1, Halle (Saale), D-06108, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Braun
authors.affiliation: Department of Community Ecology, Helmholtz-Centre for Environmental Research - UFZ Theodor-Lieser-Str. 4, Halle (Saale), D-06120, Germany ; German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig Deutscher Platz 5e, Leipzig, D-04103, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Auge
authors.affiliation: Institute of Biology/Geobotany and Botanical Garden, Martin Luther University Halle Wittenberg Am Kirchtor 1, Halle (Saale), D-06108, Germany ; German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig Deutscher Platz 5e, Leipzig, D-04103, Germany.
authors.forename: Helge
authors.initials: H
authors.lastname: Bruelheide
keywords: Kreinitz experiment; Quercus petraea; Shannon diversity effects; Tilia cordata; biodiversity and ecosystem functioning; determinants of plant community diversity and structure; disease dilution effect; fungal pathogen richness and infestation; local neighbourhood; neighbouring species identity effects