title: The importance of forest structure to biodiversity-productivity relationships.
abstract: While various relationships between productivity and biodiversity are found in forests, the processes underlying these relationships remain unclear and theory struggles to coherently explain them. In this work, we analyse diversity-productivity relationships through an examination of forest structure (described by basal area and tree height heterogeneity). We use a new modelling approach, called 'forest factory', which generates various forest stands and calculates their annual productivity (above-ground wood increment). Analysing approximately 300 000 forest stands, we find that mean forest productivity does not increase with species diversity. Instead forest structure emerges as the key variable. Similar patterns can be observed by analysing 5054 forest plots of the German National Forest Inventory. Furthermore, we group the forest stands into nine forest structure classes, in which we find increasing, decreasing, invariant and even bell-shaped relationships between productivity and diversity. In addition, we introduce a new index, called optimal species distribution, which describes the ratio of realized to the maximal possible productivity (by shuffling species identities). The optimal species distribution and forest structure indices explain the obtained productivity values quite well (R2between 0.7 and 0.95), whereby the influence of these attributes varies within the nine forest structure classes.
authors.affiliation: Department for Ecological Modelling, Helmholtz Centre for Environmental Research GmbH-UFZ, Permoserstraße 15, 04318 Leipzig, German; Institute for Environmental Systems Research, University of Osnabrück, Barbarastraße 12, 49076 Osnabrück, German.
authors.forename: Friedrich J
authors.identifier: 0000-0002-7328-1187
authors.initials: FJ
authors.lastname: Bohn
authors.affiliation: Department for Ecological Modelling, Helmholtz Centre for Environmental Research GmbH-UFZ, Permoserstraße 15, 04318 Leipzig, German; Institute for Environmental Systems Research, University of Osnabrück, Barbarastraße 12, 49076 Osnabrück, German; German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103 Leipzig, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Huth
keywords: biodiversity; ecosystem functioning; forest stand; gap model; productivity; temperate forests