insights for ecological applications from the German Biodiversity Exploratories

Biodiversity, a multidimensional property of natural systems, is difficult to quantify partly because of the multitude of indices proposed for this purpose. Indices aim to describe general properties of communities that allow us to compare different regions, taxa, and trophic levels. Therefore, they are of fundamental importance for environmental monitoring and conservation, although there is no consensus about which indices are more appropriate and informative. We tested several common diversity indices in a range of simple to complex statistical analyses in order to determine whether some were better suited for certain analyses than others. We used data collected around the focal plant Plantago lanceolata on 60 temperate grassland plots embedded in an agricultural landscape to explore relationships between the common diversity indices of species richness (S), Shannon's diversity (H'), Simpson's diversity (D1), Simpson's dominance (D2), Simpson's evenness (E), and Berger–Parker dominance (BP). We calculated each of these indices for herbaceous plants, arbuscular mycorrhizal fungi, aboveground arthropods, belowground insect larvae, and P. lanceolata molecular and chemical diversity. Including these trait-based measures of diversity allowed us to test whether or not they behaved similarly to the better studied species diversity. We used path analysis to determine whether compound indices detected more relationships between diversities of different organisms and traits than more basic indices. In the path models, more paths were significant when using H', even though all models except that with E were equally reliable. This demonstrates that while common diversity indices may appear interchangeable in simple analyses, when considering complex interactions, the choice of index can profoundly alter the interpretation of results. Data mining in order to identify the index producing the most significant results should be avoided, but simultaneously considering analyses using multiple indices can provide greater insight into the interactions in a system

Data from: Community- weighted mean plant traits predict small scale distribution of insect root herbivore abundance

Small scale distribution of insect root herbivores may promote plant species diversity by creating patches of different herbivore pressure. However, determinants of small scale distribution of insect root herbivores, and impact of land use intensity on their small scale distribution are largely unknown. We sampled insect root herbivores and measured vegetation parameters and soil water content along transects in grasslands of different management intensity in three regions in Germany. We calculated community-weighted mean plant traits to test whether the functional plant community composition determines the small scale distribution of insect root herbivores. To analyze spatial patterns in plant species and trait composition and insect root herbivore abundance we computed Mantel correlograms. Insect root herbivores mainly comprised click beetle (Coleoptera, Elateridae) larvae (43%) in the investigated grasslands. Total insect root herbivore numbers were positively related to community-weighted mean traits indicating high plant growth rates and biomass (specific leaf area, reproductive- and vegetative plant height), and negatively related to plant traits indicating poor tissue quality (leaf C/N ratio). Generalist Elaterid larvae, when analyzed independently, were also positively related to high plant growth rates and furthermore to root dry mass, but were not related to tissue quality. Insect root herbivore numbers were not related to plant cover, plant species richness and soil water content. Plant species composition and to a lesser extent plant trait composition displayed spatial autocorrelation, which was not influenced by land use intensity. Insect root herbivore abundance was not spatially autocorrelated. We conclude that in semi-natural grasslands with a high share of generalist insect root herbivores, insect root herbivores affiliate with large, fast growing plants, presumably because of availability of high quantities of food. Affiliation of insect root herbivores with large, fast growing plants may counteract dominance of those species, thus promoting plant diversity

Cinémagazine : hebdomadaire illustré

24 août 19281928/08/24 (A8,N34)-1928/08/24

Average mantel correlation coefficients.

<p>over all investigated sites with standard deviation for a) plant communities, b) trait composition and c) insect root herbivore abundance. Mantel correlograms for individual sites are given in the supplementary material.</p

The Root Herbivore History of the Soil Affects the Productivity of a Grassland Plant Community and Determines Plant Response to New Root Herbivore Attack

<div><p>Insect root herbivores can alter plant community structure by affecting the competitive ability of single plants. However, their effects can be modified by the soil environment. Root herbivory itself may induce changes in the soil biota community, and it has recently been shown that these changes can affect plant growth in a subsequent season or plant generation. However, so far it is not known whether these root herbivore history effects (i) are detectable at the plant community level and/or (ii) also determine plant species and plant community responses to new root herbivore attack. The present greenhouse study determined root herbivore history effects of click beetle larvae (Elateridae, Coleoptera, genus <i>Agriotes</i>) in a model grassland plant community consisting of six common species (<i>Achillea millefolium</i>, <i>Plantago lanceolata</i>, <i>Taraxacum officinale</i>, <i>Holcus lanatus</i>, <i>Poa pratensis</i>, <i>Trifolium repens</i>). Root herbivore history effects were generated in a first phase of the experiment by growing the plant community in soil with or without <i>Agriotes</i> larvae, and investigated in a second phase by growing it again in the soils that were either <i>Agriotes</i> trained or not. The root herbivore history of the soil affected plant community productivity (but not composition), with communities growing in root herbivore trained soil producing more biomass than those growing in untrained soil. Additionally, it influenced the response of certain plant species to new root herbivore attack. Effects may partly be explained by herbivore-induced shifts in the community of arbuscular mycorrhizal fungi. The root herbivore history of the soil proved to be a stronger driver of plant growth on the community level than an actual root herbivore attack which did not affect plant community parameters. History effects have to be taken into account when predicting the impact of root herbivores on grasslands.</p> </div

Shoot biomass (mean + se) of plants affected by the presence of <i>Agriotes</i> larvae.

<p>Phase 1 (A) <i>P. lanceolata</i> (B) <i>A. millefolium</i>; phase 2 (C) <i>P. lanceolata</i> (D) <i>A. millefolium</i>, (E) <i>T repens;</i> SEG33, SEG37: soil biota from respective grassland sites; −AP1, +AP1: untrained and <i>Agriotes</i> trained soil from phase 1, respectively.</p

Effects of soil biota community (SB, SEG 33 and SEG 37) and <i>Agriotes</i> presence (AP1, without and with) on plant and AMF parameters and soil CN in phase 1.

<p>significance level:</p>*<p>p<0.05,</p>**<p>p<0.01,</p>***<p>p<0.001,</p><p>ns = not significant, LEH: length of extraradical AMF hyphae, AMF: arbuscular mycorrhizal fungi.</p

Plant and AMF parameters and Soil CN ratio (mean (se)) in different soil treatments (soil biota communities SGE 33 and SEG 37, <i>Agriotes</i> untrained (−AP1) or trained (+AP1) soil substrate) in phase 1 and 2.

<p>gDW: gram dry weight, LEH: length of extraradical AMF hyphae, AMF: arbuscular mycorrhizal fungi, RLC: root length colonized.</p