DOI: 10.5061/dryad.847km00
title: Data from: Tree diversity increases robustness of multi-trophic interactions

description: Multi-trophic interactions maintain critical ecosystem functions.
 Biodiversity is declining globally, while responses of trophic
 interactions to biodiversity change are largely unclear. Thus, studying
 responses of multi-trophic interaction robustness to biodiversity change
 is crucial for understanding ecosystem functioning and persistence. We
 investigate plant-Hemiptera- (antagonism) and Hemiptera-ant- (mutualism)
 interaction networks in response to experimental manipulation of tree
 diversity. We show increased diversity at both higher trophic levels
 (Hemiptera and ants) and increased robustness through redundancy of lower
 level species of multi-trophic interactions when tree diversity increased.
 Hemiptera and ant diversity increased with tree diversity through
 non-additive diversity effects. Network analyses identified that tree
 diversity also increased the number of tree and Hemiptera species utilized
 by Hemiptera and ant species, and decreased the specialization on lower
 trophic level species in both mutualistic and antagonist interactions. Our
 results demonstrate that bottom-up effects of tree diversity ascend
 through trophic levels regardless of interaction type. Thus, local tree
 diversity is a key driver of multi-trophic community diversity and
 interaction robustness in forests.
description: Fornoff_2019_BEF_China_trophobiosesWe conducted field surveys for trophobiotic Hemiptera Hemiptera and tending ants at 300 plots and over 12,000 trees at the BEF-China Main Experiment. Depending on tree species identity and sampling year, tree height was between 1 and 6 m. We selected 150 plots at each of the two experimental sites (‘site A’ and ‘site B’) representing each tree species at similar proportions across all tree species richness levels. Each site was surveyed three times for the presence of Hemiptera and interacting ants (trophobiosis), site A once in 2011, site B once in 2013 and both sites twice in 2014. To avoid effects of neighbouring plots and edge-effects, our surveys used a ‘core area’ approach on the central tree individuals guaranteeing a minimum buffer distance of 5.16 m to the adjacent plot margin. The number of plots available for sampling decreased with increasing tree species richness. To sample the same number of tree individuals for each tree species in each tree species richness level, we increased the number of trees sampled per plot with increasing tree species richness, from 36 trees in monocultures to 144 trees in 24 species mixtures. At each tree individual, a total of 20 leaves from three branch sections and their bark were visually inspected for the presence of Hemiptera and interacting ants. Ants were only considered as interacting when direct tending behaviour, such as honeydew excretion in response to ant antennation or the presence of ant constructed sheetings, was observed. Each unique trophobiosis between one ant species and one Hemiptera species per leaf or bark section was defined as one interaction, regardless of the number of interaction partners involved.Fornoff_et_al_data_file_ESM.xlsx