title: Tree Species Richness Promotes Invertebrate Herbivory on Congeneric Native and Exotic Tree Saplings in a Young Diversity Experiment.
abstract: Tree diversity in forests is an important driver of ecological processes including herbivory. Empirical evidence suggests both negative and positive effects of tree diversity on herbivory, which can be, respectively, attributed to associational resistance or associational susceptibility. Tree diversity experiments allow testing for associational effects, but evidence regarding which pattern predominates is mixed. Furthermore, it is unknown if herbivory on tree species of native vs. exotic origin is influenced by changing tree diversity in a similar way, or if exotic tree species escape natural enemies, resulting in lower damage that is unrelated to tree diversity. To address these questions, we established a young tree diversity experiment in temperate southwestern Germany that uses high planting density (49 trees per plot; plot size 13 m2). The species pool consists of six congeneric species pairs of European and North American origin (12 species in total) planted in monocultures and mixtures (1, 2, 4, 6 species). We assessed leaf damage by leaf-chewing insects on more than 5,000 saplings of six broadleaved tree species. Plot-level tree species richness increased leaf damage, which more than doubled from monocultures to six-species mixtures, strongly supporting associational susceptibility. However, leaf damage among congeneric native and exotic species pairs was similar. There were marked differences in patterns of leaf damage across tree genera, and only the genera likely having a predominately generalist herbivore community showed associational susceptibility, irrespective of the geographical origin of a tree species. In conclusion, an increase in tree species richness in young temperate forests may result in associational susceptibility to feeding by generalist herbivores.
authors.affiliation: Department of Nature Conservation and Landscape Ecology, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg, Germany.
authors.forename: Annika
authors.initials: A
authors.lastname: Wein
authors.affiliation: Department of Silviculture, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Bauhus
authors.affiliation: Centre for Forest Research, Université du Québec à Montréal, Centre-ville Station, QC H3C 3P8 Montréal, Canada.
authors.forename: Simon
authors.initials: S
authors.lastname: Bilodeau-Gauthier
authors.affiliation: Department of Geobotany, Faculty of Biology, University of Freiburg, Freiburg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Scherer-Lorenzen
authors.affiliation: Department of Silviculture, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg, Germany.|Department of Geobotany, Faculty of Biology, University of Freiburg, Freiburg, Germany.
authors.forename: Charles
authors.initials: C
authors.lastname: Nock
authors.affiliation: Department of Nature Conservation and Landscape Ecology, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg, Germany.
authors.forename: Michael
authors.identifier: http://orcid.org/0000-0003-0894-7576
authors.initials: M
authors.lastname: Staab
mesh_terms: D000818:Animals; D044822:Biodiversity; D065928:Forests; D060434:Herbivory; D007313:Insecta / Q000502:physiology*; D000069600:Plant Breeding; D014197:Trees / Q000145:classification* / Q000254:growth & development*