title: Fungal disease incidence along tree diversity gradients depends on latitude in European forests.
abstract: European forests host a diversity of tree species that are increasingly threatened by fungal pathogens, which may have cascading consequences for forest ecosystems and their functioning. Previous experimental studies suggest that foliar and root pathogen abundance and disease severity decrease with increasing tree species diversity, but evidences from natural forests are rare. Here, we tested whether foliar fungal disease incidence was negatively affected by tree species diversity in different forest types across Europe. We measured the foliar fungal disease incidence on 16 different tree species in 209 plots in six European countries, representing a forest-type gradient from the Mediterranean to boreal forests. Forest plots of single species (monoculture plots) and those with different combinations of two to five tree species (mixed species plots) were compared. Specifically, we analyzed the influence of tree species richness, functional type (conifer vs. broadleaved) and phylogenetic diversity on overall fungal disease incidence. The effect of tree species richness on disease incidence varied with latitude and functional type. Disease incidence tended to increase with tree diversity, in particular in northern latitudes. Disease incidence decreased with tree species richness in conifers, but not in broadleaved trees. However, for specific damage symptoms, no tree species richness effects were observed. Although the patterns were weak, susceptibility of forests to disease appears to depend on the forest site and tree type.
authors.affiliation: Department of Forest Mycology and Plant Pathology Swedish University of Agricultural Sciences Box 7026 75007 Uppsala Sweden.
authors.forename: Diem
authors.identifier: 0000-0002-9680-5772
authors.initials: D
authors.lastname: Nguyen
authors.affiliation: BIOGECO University of Bordeaux UMR 1202 33615 Pessac France; INRA BIOGECO UMR 1202 33612 Cestas France.
authors.forename: Bastien
authors.initials: B
authors.lastname: Castagneyrol
authors.affiliation: Institute of Biology/Geobotany and Botanical Garden Martin Luther University Halle-Wittenberg 06108 Halle Germany; German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig 04103 Leipzig Germany.
authors.forename: Helge
authors.initials: H
authors.lastname: Bruelheide
authors.affiliation: Department of Agricultural Food and Environmental Sciences University of Firenze 50144 Firenze Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Bussotti
authors.affiliation: INRA BIOGECO UMR 1202 33612 Cestas France; INRA DYNAFOR UMR 1201 31326 Castanet-Tolosan France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Guyot
authors.affiliation: BIOGECO University of Bordeaux UMR 1202 33615 Pessac France; INRA BIOGECO UMR 1202 33612 Cestas France.
authors.forename: Hervé
authors.initials: H
authors.lastname: Jactel
authors.affiliation: Białowieża Geobotanical Station Faculty of Biology University of Warsaw 17230 Warsaw Poland.
authors.forename: Bogdan
authors.initials: B
authors.lastname: Jaroszewicz
authors.affiliation: Museo Nacional de Ciencias Naturales Consejo Superior de Investigaciones Cientificas 28006 Madrid Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Valladares
authors.affiliation: Department of Forest Mycology and Plant Pathology Swedish University of Agricultural Sciences Box 7026 75007 Uppsala Sweden.
authors.forename: Jan
authors.initials: J
authors.lastname: Stenlid
authors.affiliation: Department of Forest Mycology and Plant Pathology Swedish University of Agricultural Sciences Box 7026 75007 Uppsala Sweden.
authors.forename: Johanna
authors.initials: J
authors.lastname: Boberg
keywords: Diversity gradient; Europe; FunDivEUROPE; foliar fungal pathogen; forests; latitudinal gradient; tree species richness