Foliar herbivory on plants creates soil legacy effects that impact future insect herbivore growth via changes in plant community biomass allocation

1. Plants leave legacy effects in the soil they grow in, which can drive important vegetation processes, including productivity, community dynamics and species turnover. Plants at the same time also face continuous pressure posed by insect herbivores. Given the intimate interactions between plants and herbivores in ecosystems, plant identity and herbivory are likely to interactively shape soil legacies. However, the mechanisms that drive such legacy effects on future generations of plants and associated herbivores are little known.2. In a greenhouse study, we exposed 10 common grasses and non-leguminous forbs individually to insect herbivory by two closely related noctuid caterpillars, Mamestra brassicae and Trichoplusia ni (Lepidoptera: Noctuidae) or kept them free of herbivores. We then used the soil legacies created by these plant individuals to grow a plant community composed of all 10 plant species in each soil and exposed these plant communities to M. brassicae. We measured conditioning plant biomass, soil respiration and chemistry of the conditioned soils, as well as individual plant, plant community and herbivore biomass responses.3. At the end of the conditioning phase, soils with herbivore legacies had higher soil respiration, but only significantly so for M. brassicae. Herbivore legacies had minimal impacts on community productivity. However, path models reveal that herbivore-induced soil legacies affected responding herbivores through changes in plant community shoot: root ratios. Soil legacy effect patterns differed between functional groups. We found strong plant species and functional group-specific effects on soil respiration parameters, which in turn led to plant community shifts in grass: forb biomass ratios. Soil legacies were negative for the growth of plants of the same functional group.4. Synthesis. We show that insect herbivory, plant species and their functional groups, all incur soil microbial responses that lead to subtle (herbivory) or strong (plants and their functional group) effects in response plant communities and associated polyphagous herbivores. Hence, even though typically ignored, our study emphasizes that legacies of previous insect herbivory in the soil can influence current soil–plant–insect community interactions.Plant science

On two subgroups of U(n), useful for quantum computing

As two basic building blocks for any quantum circuit, we consider the 1-qubit PHASOR circuit Phi(theta) and the 1-qubit NEGATOR circuit N(theta). Both are roots of the IDENTITY circuit. Indeed: both (NO) and N(0) equal the 2 x 2 unit matrix. Additionally, the NEGATOR is a root of the classical NOT gate. Quantum circuits (acting on w qubits) consisting of controlled PHASORs are represented by matrices from ZU(2(w)); quantum circuits consisting of controlled NEGATORs are represented by matrices from XU(2(w)). Here, ZU(n) and XU(n) are subgroups of the unitary group U(n): the group XU(n) consists of all n x n unitary matrices with all 2n line sums (i.e. all n row sums and all n column sums) equal to 1 and the group ZU(n) consists of all n x n unitary diagonal matrices with first entry equal to 1. Any U(n) matrix can be decomposed into four parts: U = exp(i alpha) Z(1)XZ(2), where both Z(1) and Z(2) are ZU(n) matrices and X is an XU(n) matrix. We give an algorithm to find the decomposition. For n = 2(w) it leads to a four-block synthesis of an arbitrary quantum computer

Discretional policies and transparency of qualifications: changing Europe without money and without States?

The paper aims to contribute to the European education policy literature through an analysis of what I refer to as ‘discretional policies’, which are now instrumentally used by the EU but that have so far been largely overlooked by this literature, and to the literature on transparency of qualifications. The paper argues, first, that the education policy literature—as other policy literatures—has overlooked individual ‘discretional policies’, to which greater attention should now be paid as they are employed by EU institutions to bypass Member States in particularly difficult policy areas and to try to address their often alleged detachment from citizens. Second, the paper looks at the crucial aspect of the effectiveness of discretionary policies and their consequences for individuals and Member States, with reference to a case study of the Europass framework in education and training

Verkenning van en beleidsuitdagingen voor de Vlaamse arbeidsmarkt in de periode 2004-2010

status: publishe

Real-time Feynman path integral with Picard–Lefschetz theory and its applications to quantum tunneling, Annals Phys

Picard–Lefschetz theory is applied to path integrals of quantum mechanics, in order to compute real-time dynam-ics directly. After discussing basic properties of real-time path integrals on Lefschetz thimbles, we demonstrate its computational method in a concrete way by solving three simple examples of quantum mechanics. It is applied to quantum mechanics of a double-well potential, and quantum tunneling is discussed. We identify all of the complex saddle points of the classical action, and their properties are discussed in detail. However a big theoretical difficulty turns out to appear in rewriting the original path integral into a sum of path integrals on Lefschetz thimbles. We dis-cuss generality of that problem and mention its importance. Real-time tunneling processes are shown to be described by those complex saddle points, and thus semi-classical description of real-time quantum tunneling becomes possible on solid ground if we could solve that problem

Taking plant–soil feedbacks to the field in a temperate grassland

Plant–soil feedbacks (PSFs) involve changes to the soil wrought by plants, which change biotic and abiotic properties of the soil, affecting plants that grow in the soil at a later time. The importance of PSFs for understanding ecosystem functioning has been the focus of much recent research, for example, in predicting the consequences for agricultural production, biodiversity conservation, and plant population dynamics. Here, we describe an experiment designed to test PSFs left by plants with contrasting traits under field conditions. This is one of the first, large-scale field experiments of its kind. We removed the existent plant community and replaced it with target plant communities that conditioned the soil. These communities consisted of contrasting proportions of grass and forb cover and consisted of either fast- or slow-growing plants, in accordance with the plant economics spectrum. We chose this well-established paradigm because plants on opposite ends of this spectrum have developed contrasting strategies to cope with environmental conditions. This means they differ in their feedbacks with soil abiotic and biotic factors. The experimental procedure was repeated in two successive years in two different subplots in order to investigate temporal effects on soils that were conditioned by the same plant community. Our treatments were successful in creating plant communities that differed in their total percentage cover based on temporal conditioning, percentage of grasses versus forbs, and percentage of fast- versus slow-growing plants. As a result, we expect that the influence of these different plant communities will lead to different PSFs. The unique and novel design of this experiment allows us to simultaneously test for the impacts of temporal effects, plant community composition and plant growth strategy on PSFs. Here, we describe the experimental design and demonstrate why this effective design is ideal to advance our understanding of PSFs in the field

‘Home’ and ‘away’ litter decomposition depends on the size fractions of the soil biotic community

Plant science