On the trails of Josias Braun-Blanquet : changes in the grasslands of the inneralpine dry valleys during the last 70 years. First results from the 11th EDGG Field Workshop in Austria

The 11th EDGG Field Workshop was held from 6 to 13 July 2018 in Austria. Its aim was to revisit dry grasslands in the inneralpine dry valleys of Austria that were investigated in the late 1950s by Braun-Blanquet and to collect high-quality biodiversity data from these. Sampling was carried out in the Styrian Mur Valley, the Virgen Valley in East Tyrol, the Upper Inn Valley in the Austrian Eastern Alps, and Griffen in Carinthia. In total, we sampled 15 EDGG biodiversity plots and 37 additional 10 m2 plots. Butterfly data were record-ed in four biodiversity plots and two additional plots. We found maximum richness values of 49, 68 and 95 vascular plant species on 1, 10 and 100 m², while the corresponding values for the complete terrestrial vegetation were 56, 73 and 106 species. Maximum butterfly richness was 19, but it was in general quite low, and generalists dominated. Some of the areas originally studied by Braun-Blanquet were no longer dry grasslands and only a few sites remained largely unchanged. Detrended Correspondence Analysis (DCA) showed profound changes between the old (1950s and 1980s) and our current plots. Without grazing or other human land management activities, only very small cores of rocky dry grassland could survive in the comparatively humid Austrian inneralpine valleys. Finally, the sampled data raise questions about the syntaxonomic position of some of the grasslands, which needs to be addressed in a more comprehensive study, which is planned as the next step

Development of an instrument for measuring the complexity of learning tasks

An instrument for measuring the complexity of learning tasks in the field of Law was developed and tested in three experiments. In Experiments 1 and 2, teachers used the card-sort method to rate the complexity of learning tasks. Based on the outcomes, a benchmark scale with four criterion tasks was used in Experiment 3. The results showed the benchmark instrument to be valid and easy to use, allowing instructional designers to design competency-based learning environments that better take task complexity into account. The Instructional Design model, in which teachers determine task complexity, is briefly described

Separating Exchange Splitting from Spin Mixing in Gadolinium by Femtosecond Laser Excitation

Employing spin-, time-, and energy-resolved photoemission spectroscopy, we present the first study on the spin polarization of a single electronic state after ultrafast optical excitation. Our investigation concentrates on the majority-spin component of the d-band-derived Gd(0001) surface state d↑z2. While its binding energy shows a rapid Stoner-like shift by 90 meV with an exponential time constant of τE=0.6±0.1  ps, the d↑z2 spin polarization remains nearly constant within the first picoseconds and decays with τS=15±8 ps. This behavior is in clear contrast to the equilibrium phase transition, where the spin polarization vanishes at the Curie temperature

Proposal of a standardized EDGG surveying methodology for orthopteroid insects

Orthopteroid insects (Caelifera, Ensifera, Mantodea) are characteristic of grassland ecosystems. They are often key species in grassland food webs, and many species have very specific requirements concerning habitat structure. Thus, orthopteroid insects are valued and widely used indicators in grassland ecology. Here we propose a standardised surveying methodology for orthopteroid insects in EDGG Biodiversity Plots. A variety of methods to survey orthopteroid insects have been used in the past, most of them based on sweep netting along a defined transect. The method proposed here is also based on this principle, but additionally utilises an exhaustive search to capture total species richness and estimate the frequency of the surveyed species. The method can be used in any grassland survey that is based on EDGG Biodiversity Plot and similar sampling designs. It was tested during the EDGG Field Workshop 2019 in Armenia, and has proven its applicability in a wide range of different grassland types

Atomic and electronic structure of bismuth-bilayer-terminated Bi2Se3(0001) prepared by atomic hydrogen etching

A bilayer of bismuth is recognized as a prototype two-dimensional topological insulator. Here we present a simple and well reproducible top-down approach to prepare a flat and well ordered bismuth bilayer with a lateral size of several hundred nanometers on Bi2Se3(0001). Using scanning tunneling microscopy, surface x-ray diffraction, and Auger electron spectroscopy we show that exposure of Bi2Se3(0001) to atomic hydrogen completely removes selenium from the top quintuple layer. The band structure of the system, calculated from first principles for the experimentally derived atomic structure, is in excellent agreement with recent photoemission data. Our results open interesting perspectives for the study of topological insulators in general

Spin-texture inversion in the giant Rashba semiconductor BiTeI

Semiconductors with strong spin-orbit interaction as the underlying mechanism for the generation of spin-polarized electrons are showing potential for applications in spintronic devices. Unveiling the full spin texture in momentum space for such materials and its relation to the microscopic structure of the electronic wave functions is experimentally challenging and yet essential for exploiting spin-orbit effects for spin manipulation. Here we employ a state-of-the-art photoelectron momentum microscope with a multichannel spin filter to directly image the spin texture of the layered polar semiconductor BiTeI within the full two-dimensional momentum plane. Our experimental results, supported by relativistic ab initio calculations, demonstrate that the valence and conduction band electrons in BiTeI have spin textures of opposite chirality and of pronounced orbital dependence beyond the standard Rashba model, the latter giving rise to strong optical selection-rule effects on the photoelectron spin polarization. These observations open avenues for spin-texture manipulation by atomic-layer and charge carrier control in polar semiconductors.This work was supported by DFG (through SFB 1170 'ToCoTronics') and through FOR1162 (P3). We acknowledge the support by the Basque Departamento de Educacion, UPV/EHU (Grant Number IT-756-13), Spanish Ministerio de Economia y Competitividad (MINECO Grant Number FIS2013-48286-C2-2-P), Tomsk State University Academic D.I. Mendeleev Fund Program in 2015 (Research Grant Number 8.1.05.2015), the Russian Foundation for Basic Research (Grant Numbers 15-02-01797 and 15-02-589 02717). Partial support by the Saint Petersburg State University (Grant Number 15.61.202.2015) is also acknowledged

Surface spin polarization of the non-stoichiometric Heusler compound Co2Mn(alpha)Si

Using a combined approach of spin-resolved photoemission spectroscopy, band structure and photoemission calculations we investigate the influence of bulk defects and surface states on the spin polarization of Co2Mn(alpha)Si thin films with bulk L21 order. We find that for Mn-poor alloys the spin polarization at EF is negative due to the presence of Co_Mn antisite and minority surface state contributions. In Mn-rich alloys, the suppression of Co(Mn) antisites leads to a positive spin polarization at the Fermi energy, and the influence of minority surface states on the photoelectron spin polarization is reduced

GrassPlot v. 2.00 – first update on the database of multi-scale plant diversity in Palaearctic grasslands

Abstract: GrassPlot is a collaborative vegetation-plot database organised by the Eurasian Dry Grassland Group (EDGG) and listed in the Global Index of Vegetation-Plot Databases (GIVD ID EU-00-003). Following a previous Long Database Report (Dengler et al. 2018, Phyto- coenologia 48, 331–347), we provide here the first update on content and functionality of GrassPlot. The current version (GrassPlot v. 2.00) contains a total of 190,673 plots of different grain sizes across 28,171 independent plots, with 4,654 nested-plot series including at least four grain sizes. The database has improved its content as well as its functionality, including addition and harmonization of header data (land use, information on nestedness, structure and ecology) and preparation of species composition data. Currently, GrassPlot data are intensively used for broad-scale analyses of different aspects of alpha and beta diversity in grassland ecosystems