Recent advances in exploring physiology and biodiversity of ectomycorrhizas highlight the functioning of these symbioses in ecosystems

Ectomycorrhizas, the dominating mycorrhizal symbiosis in boreal, temperate and some tropical forests, are formed by 5000-6000 species of the asco- and basidiomycetes. This high diversity of fungal partners allows optimal foraging and mobilisation of various nitrogen and phosphorus forms from organic soil layers. In this review, two approaches to study the functioning of this multitude of symbiotic associations are presented. On selected culture models, physiological and molecular investigations have shown that the supply of hexoses has a key function in controlling the plant^fungus interaction via partner-specific regulation of gene expression. Environmental factors which affect fungal carbon supply, such as increased nitrogen availability, also affect mycorrhiza formation. Based on such laboratory results, the adaptative capability of ectomycorrhizas to changing field conditions is discussed. The second approach consists of analysing the distribution of mycorrhizas in ecosystem compartments and to relate distribution patterns to variations of ecological factors. Recent advances in identification of fungal partners in ectomycorrhizas by analysing the internal transcribed spacer of ribosomal DNA are presented, which can help to resolve sampling problems in field studies. The limits of the laboratory and the field approaches are discussed. Despite some problems, this combined approach is the most promising. Direct investigation of gene expression, which has been introduced for soil bacteria, will be difficult in the case of mycorrhizal fungi which constitute organisms with functionally varying structure

Arbuscular mycorrhizas in phosphate-polluted soil: interrelations between root colonization and nitrogen

To investigate whether arbuscular mycorrhizal fungi (AMF) – abundant in a phosphate-polluted but nitrogen-poor field site – improve plant N nutrition, we carried out a two-factorial experiment, including N fertilization and fungicide treatment. Percentage of root length colonized (% RLC) by AMF and tissue element concentrations were determined for four resident plant species. Furthermore, soil nutrient levels and N effects on aboveground biomass of individual species were measured. Nitrogen fertilization lowered % RLC by AMF of Artemisia vulgaris L., Picris hieracioides L. and Poa compressa L., but not of Bromus japonicus Thunb. This – together with positive N addition effects on N status, N:P-ratio and aboveground biomass of most species – suggested that plants are mycorrhizal because of N deficiency. Fungicide treatment, which reduced % RLC in all species, resulted in lower N concentrations in A. vulgaris and P. hieracioides, a higher N concentration in P. compressa, and did not consistently affect N status of B. japonicus. Evidently, AMF had an influence on the N nutrition of plants in this P-rich soil; however – potentially due to differences in their mycorrhizal responsiveness – not all species seemed to benefit froma mycorrhiza-mediated N uptake and accordingly, N distribution

Forest age and plant species composition determine the soil fungal community composition in a Chinese subtropical forest

Non peer reviewedPublisher PD

Choosing And Using Diversity Indices: 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\u27s diversity (H\u27), Simpson\u27s diversity (D1), Simpson\u27s dominance (D2), Simpson\u27s 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\u27, 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

Livres et livrets sur les fêtes princières à l’époque du Reichsland Elsass-Lothringen

Si les fêtes impériales qui ont lieu dans le Reichsland Elsass-Lothringen constituent un outil au service de la (re)germanisation des esprits, cette remarque vaut tout autant pour les livres, livrets et brochures qui en relatent le contenu et en prolongent le souvenir. Ce type d’ouvrages va fleurir en Alsace et en Lorraine entre 1871 et 1918. Leur stratégie pédagogique est de créer l’impression d’une continuité historique avec des fêtes princières germaniques beaucoup plus anciennes, ce qui revient à minimiser ou à nier la « parenthèse » française qu’ont connu l’Alsace et la Lorraine depuis la Paix de Westphalie.If the imperial festivities that took place in Reichsland Elsass-Lothringen, were instrumental in the re-Germanization of mentalities, the same can be said for the written accounts found in books, booklets and brochures where the past was made to live on in memory. Such written works came to flourish in Alsace and Lorraine between 1871 and 1918 whose pedagogical purpose was to invent the historical fiction of an unbroken line going back to the German imperial festivities of ancient times. This amounted to minimizing and denying the intervening “interlude” after the Peace of Westphalia when Alsace and Lorraine turned French.Dienten die kaiserlichen Feierlichkeiten im Reichsland Elsass-Lothringen der (Re)-Germanisierung der Bevölkerung, so gilt dies umso mehr für die Publikationen, die darüber berichteten und die so die Erinnerung an sie bewahren helfen sollten. Solche Publikationen (Bücher, Broschüren und kleine Heftchen) erschienen im Elsass und in Lothringen im Zeitraum zwischen 1871 und 1918 in großer Zahl. Ihre didaktische Strategie war es, eine Kontinuitätslinie zu den deutschen kaiserlichen Festen der Vergangenheit zu ziehen und damit die französische das französische „Zwischenspiel”, also den Zeitraum vom Westfälischen Frieden bis zur Reichsgründung, während dem das Elsass und Lothringen zu Frankreich gehört hatten, zu minimieren oder ganz zu leugnen

Introduction

Si, depuis plusieurs décennies, les fêtes traditionnelles fascinent les historiens, et plus généralement les chercheurs en sciences humaines, c’est qu’à bien des égards, elles nous sont devenues étrangères. Nos sociétés occidentales n’ont certes pas complètement désappris l’art de la fête ; mais de plus en plus, les notions de vie privée, de temps libre, de « vacances » (au sens littéral du terme) prennent le pas sur les célébrations calendaires et collectives qui ont longtemps rythmé la vie ..

Bernd Wegner, Das deutsche Paris. Der Blick der Besatzer 1940-1944

Der Blick der Besatzer, ouvrage écrit par l’historien Bernd Wegner, richement illustré par des documents authentiques, frappe dès l’abord par son originalité. À commencer par celle de l’objet d’étude : l’occupation allemande de la capitale durant la Seconde Guerre mondiale a été certes souvent analysée du point de vue du Paris occupé, mais beaucoup moins de celui de l’occupant. Originalité de la démarche, ensuite : s’appuyant tout à la fois sur un nombre impressionnant de lettres, de témoigna..

Molecular screening of microorganisms associated with discolored wood in dead European beech trees suffered from extreme drought event using next generation sequencing

Drought events weaken trees and make them vulnerable to attacks by diverse plant pathogens. Here, we propose a molecular method for fast screening of microorganisms associated with European beech decline after an extreme drought period (2018) in a forest of Thuringia, Germany. We used Illumina sequencing with a recent bioinformatics approach based on DADA2 to identify archaeal, bacterial, and fungal ASVs (amplicon sequence variants) based on bacterial and archaeal 16S and fungal ITS genes. We show that symptomatic beech trees are associated with both bacterial and fungal plant pathogens. Although the plant pathogen sequences were detected in both discolored and non-discolored wood areas, they were highly enriched in the discolored wood areas. We show that almost each individual tree was associated with a different combination of pathogens. Cytospora spp. and Neonectria coccinea were among the most frequently detected fungal pathogens, whereas Erwinia spp. and Pseudomonas spp. were the dominant bacterial plant pathogens. We demonstrate that bacterial plant pathogens may be of major importance in beech decline

Temporal Changes and Alternating Host Tree Root and Shoot Growth Affect Soil Microbiomes

Patterns of trees’ endogenous rhythmic growth (ERG) and paralleled C allocation shift between root and shoot systems have been studied, but there is still a need to understand their impact in shaping soil microbiomes. Moreover, the impact of plants on soil microbial communities can be modulated or overweighed by time-induced plant and/or seasonal changes. Thus, we intended to analyze the structure of soil microbiomes as response to simultaneous alternated host tree root and shoot flushes and time-induced changes within one vegetation period at two sites in Central Germany. In this study, we utilized oak phytometers (Quercus robur L., clone DF159) as host trees, and made use of their ERG, whereby consecutive root and shoot flushes make a complete growth cycle. We studied two complete growth cycles during the same vegetation period, performed a non-destructive soil sampling and applied high-throughput amplicon sequencing of the bacterial 16S gene and the fungal ITS2 region. As C allocation shifts between the tree root and shoot, released root exudates and consequently the nutrient availability alternate for soil microorganisms. We therefore anticipated different microbial communities in the host tree root zone along the growth cycles until autumnal leaf senescence. In our results, the bacterial community exhibited a directional change over time along the vegetation period. In contrast, the fungal community appeared sample specific. Our findings enlarge the current understanding of the temporal microbial assembly in the host tree root zone