Correlations among plant traits often reflect important trade‐offs or allometric relationships in biological functions like carbon gain, support, water uptake, and reproduction that are associated with different plant organs. Whether trait correlations can be aggregated to “spectra” or “leading dimensions,” whether these dimensions are consistent across plant organs, spatial scale, and growth forms are still open questions. To illustrate the current state of knowledge, we constructed a network of published trait correlations associated with the “leaf economics spectrum,” “biomass allocation dimension,” “seed dimension,” and carbon and nitrogen concentrations. This literature‐based network was compared to a network based on a dataset of 23 traits from 2,530 individuals of 126 plant species from 381 plots in Northwest Europe. The observed network comprised more significant correlations than the literature‐based network. Network centrality measures showed that size traits such as the mass of leaf, stem, below‐ground, and reproductive tissues and plant height were the most central traits in the network, confirming the importance of allometric relationships in herbaceous plants. Stem mass and stem‐specific length were “hub” traits correlated with most traits. Environmental selection of hub traits may affect the whole phenotype. In contrast to the literature‐based network, SLA and leaf N were of minor importance. Based on cluster analysis and subsequent PCAs of the resulting trait clusters, we found a “size” module, a “seed” module, two modules representing C and N concentrations in plant organs, and a “partitioning” module representing organ mass fractions. A module representing the plant economics spectrum did not emerge. Synthesis. Although we found support for several trait dimensions, the observed trait network deviated significantly from current knowledge, suggesting that previous studies have overlooked trait coordination at the whole‐plant level. Furthermore, network analysis suggests that stem traits have a stronger regulatory role in herbaceous plants than leaf traits.

Lake Alaotra wetlands: how long can Madagascar's most important rice and fish production region withstand the anthropogenic pressure?

Microclimate in different positions on a host plant has strong direct effects on herbivores. But little is known about indirect effects due to changes of leaf traits. We hypothesized that herbivory increases from upper canopy to lower canopy and understory due to a combination of direct and indirect pathways. Furthermore, we hypothesized that herbivory in the understory differs between tree species in accordance with their leaf traits. We investigated herbivory by leaf chewing insects along the vertical gradient of mixed deciduous forest stands on the broad-leaved tree species Fagus sylvatica L. (European beech) with study sites located along a 140 km long transect. Additionally, we studied juvenile Acer pseudoplatanus L. (sycamore maple) and Carpinus betulus L. (hornbeam) individuals within the understory as a reference of leaf traits in the same microclimate. Lowest levels of herbivory were observed in upper canopies, where temperatures were highest. Temperature was the best predictor for insect herbivory across forest layers in our study. However, the direction was opposite to the generally known positive relationship. Herbivory also varied between the three tree species with lowest levels for F. sylvatica. Leaf carbon content was highest for F. sylvatica and probably indicates higher amounts of phenolic defense compounds. We conclude that the effect of temperature must have been indirect, whereby the expected higher herbivory was suppressed due to unfavorable leaf traits (lower nitrogen content, higher toughness and carbon content) of upper canopy leaves compared to the understory.

Most semi-natural open habitats in Europe have been traditionally maintained by anthropogenic activities, such as grazing or mowing, preventing the establishment of woody vegetation. These habitats harbour a remarkably rich biodiversity in terms of both plant and animal species, but are also highly threatened, mainly by agricultural intensification and land abandonment. With this Editorial we introduce a Special Issue initiated by the European Dry Grassland Group (EDGG) at the Open Landscapes Conference (Hildesheim, 2013) and the 11th European Dry Grassland Meeting (Kulikovo Pole, 2014). We aim to give a short introduction to the current conservation status, significance and research of semi-natural open habitats in Europe and present the collected articles of the Special Issue. These papers cover a wide range of different semi-natural open habitats, including wood-pastures, heathlands, steppes, semi-dry and dry grasslands across the Palearctic region and address issues related to the assessment methods, threats, management and restoration of these habitats. We conclude that, in order to ensure their conservation and to monitor the changes in open habitats, integrative approaches are needed that take into account not only vegetation records, but also multiple animal taxa, abiotic factors, management practices, ecosystem services and modelling simulations for anticipating possible future scenarios. We also recommend that decision-makers should support actions to conserve open habitats in Europe by addressing such major challenges as the encroachment of woody vegetation. We are convinced that the present Special Issue will contribute to a better understanding of ecosystem functions and support the biodiversity conservation and management of semi-natural open habitats.