Browsing by Author "Becker, Thomas"

Im Rahmen eines Ökosystem-Forschungsprojektes in der Nähe von Göttingen wurden 1980 auf fest markierten Flächen eines artenreichen Kalkbuchenwaldes (Hordelymo-Fagetum lathyretosum) 41 Vegetationsaufnahmen gemacht, in den Jahren 2001 und 2016 wiederholt und nun als Zeitreihe verglichen. In allen Schichten wurden signifikante Veränderungen von Struktur und Artenzusammensetzung festgestellt. Nach hohen Deckungsgraden einzelner krautiger Arten wurden 1980 verschiedene Dominanztypen (DT) unterschieden. Die unterschiedliche Zuordnung der 41 Aufnahmen im Zeitverlauf zu diesen DT wies bereits auf strukturelle Veränderungen hin. Vor allem der zunächst bestimmende Mercurialis perennis-DT hat sich zum Allium ursinum- oder Anemone nemorosa-DT hin verschoben (Tab. 1–2). Im Gesamtvergleich (Tab. 3–4) zeigen sich weitere strukturelle und floristische Veränderungen. Die von Fagus sylvatica beherrschte Baumschicht entwickelte ein dichteres Kronendach. Die Einzäunung der gesamten Untersuchungsfläche leitete wegen Ausschluss des Wildverbisses die Ausbildung einer Strauchschicht, vorwiegend aus Jungbäumen ein. Die statistisch ausgewerteten Veränderungen in der Krautschicht ergaben Artengruppen unterschiedlicher Dynamik: 15 Gewinner, 20 Verlierer und 18 konstante Arten. Ein Literaturvergleich zeigt teilweise sehr ähnliche Ergebnisse (Tab. 5). Die Gesamtartenzahl aller Flächen nahm von 1980 bis 2016 von 63 auf 58 ab. Funktionelle Eigenschaften (Lebensformen, Blattausdauer; Abb. 2–3) zeigen nur geringe Veränderungen. Fast alle Krautigen gehören zu Artengruppen mit starker Waldbindung (Abb. 3). Die Auswertung ökologischer Zeigerwerte (Abb. 4) lässt die Entwicklung zu einem stärker schattigen und luftfeuchten Mikroklima vermuten. Eine Gradientenanalyse (NMDS) zeigt ebenfalls deutliche zeitliche Veränderungen (Abb. 5). Als Hauptursache der Vegetationsveränderungen wird die langzeitige Forstgeschichte angenommen, d. h. der Übergang von extensiver Mittelwald- zu Hochwaldwirtschaft innerhalb von etwa 100 Jahren. Der Klimawandel ist derzeit vor allem in der Verfrühung und Verlängerung der Frühlings-Phänophasen erkennbar und hat u. a. die Frühlingsgeophyten gefördert. Die oft beschriebenen Eutrophierungswirkungen durch atmosphärische N-Einträge scheinen hier hingegen keine größere Rolle zu spielen. Trotz sich wandelnder Umweltbedingungen in fast 40 Jahren hat sich die grundlegende Struktur und Artenzusammensetzung des Bestandes bisher kaum verändert.

Background and aims: Aggregation of alpha-synuclein (a-syn) has been implicated in the development of neurodegenerative diseases including its spread from the enteric nervous system (ENS) to the brain. Physiologically, a-syn is located at the presynapse and might be involved in regulating of neurotransmission. Therefore, the aim of the study was to characterize the physiological ontogenetic and locoregional expression pattern of a-syn in the ENS and its association with the synaptic vesicle apparatus. Material and methods: Ontogenetic mRNA expression of a-syn and synaptophysin was determined in the rat intestine. Myenteric plexus cultures treated with glial cell line-derived neurotrophic factor (GDNF) were assessed for mRNA expression of a-syn, co-localization of a-syn with the pan-neuronal marker PGP 9.5 and the synaptic vesicle marker synaptophysin and studied by scanning electron microscopy (SEM). Human colonic specimens were subjected to co-localization studies of a-syn with synaptophysin. Results: a-syn and synaptophysin intestinal gene expression levels were highest during early postnatal life and also detectable at adult age. a-syn was co-localized with PGP 9.5 and synaptophysin in myenteric plexus cultures and up-regulated after GDNF treatment. SEM confirmed the presence of neuronal varicosities to which a-syn was associated. Consistently, a-syn and synaptophysin showed partial co-localization in the human ENS. Conclusions: The ontogenetic and cellular expression pattern as well as the regulation by GNDF give evidence that a-syn is physiologically associated to the synaptic vesicle apparatus. The data suggest that a-syn is involved in the regulation of synaptic plasticity in the ENS during early postnatal life and adult age. (C) 2015 Elsevier B.V. All rights reserved.

Semi-natural grassland supports a large proportion of biodiversity and ecosystem services in Europe, however, it is continuing to be destroyed or degraded. In addition to the clear role of local management in these processes, there is increasing evidence for wider landscape-scale effects on species richness and community composition of plants and animals. Most of this evidence comes from studies in highly altered western European landscapes with only fragments of remaining semi-natural grassland. In contrast, Eastern European countries such as Romania still contain large areas of semi-natural grassland, but this habitat is threatened by agricultural intensification and homogenization. We analyzed vascular plant and Orthoptera communities from species-rich pastures in Southern Transylvania, Romania, against a range of local and landscape factors. Species richness of plants had a highly significant positive relationship with landscape heterogeneity. Orthoptera species richness and abundance were negatively correlated with plant species richness, and increased with proportion of grassland in the landscape and local vegetation height. The results suggest that large and species-rich grassland communities can be significantly affected by both local and landscape scale land use changes, but effects can vary within and between taxonomic groups. Conservation measures such as agri-environment schemes should therefore seek to address landscape scale processes better, promoting a range of low-intensity land use practices in order to support a variety of landscape types.

Question The intensification of crop cultivation in much of Europe since the mid‐20th century has greatly increased crop yields but caused dramatic biodiversity losses in arable fields. We investigated the extent of these losses at the level of plant community types. Location Ten areas in central Germany with different soil/climate conditions and various arable plant communities. Methods We compiled historical surveys of arable fields in the 1950s/early 1960s before the onset of pervasive agricultural industrialization, and in 2009 revisited 392 arable fields. Historical and recent data were compared with supervised manual classification, detrended correspondence analysis (DCA) and ANOVA. Results Ten out of 16 plant communities at association rank observed in fields in the 1950s/1960s were not recorded again. The proportion of relevés assignable at association level decreased from 75% to 5%, while the proportion of relevés assignable only at higher syntaxon level or not assignable at all had increased from 2% to 75%. The impoverishment of vegetation was slightly less pronounced at field margins, where around one quarter of the recent relevés could be assigned to associations. Present arable plant communities in the region are species‐poor and consist chiefly of common, often herbicide‐tolerant, generalist species, with no clear preference for cereal vs root crops, autumn‐ vs spring‐sown crops or base‐rich vs base‐poor soils. Conclusion Our new approach using phytosociological syntaxa and a semi‐permanent plot design enabled us to quantify biodiversity losses at the community type level. The currently used set of phytosociological associations is inadequate to represent present‐day arable plant assemblages. The concept of residual plant communities provides a useful methodological supplement.

Der Wandel und die Verarmung der Makrophyten-Vegetation nordwestdeutscher Fließgewässer wurde durch Wiederholungsaufnahmen in 70 Bächen und Flüssen aus 4 Regionen der nordwestdeutschen Tiefebene bis zur Mittelgebirgsschwelle untersucht. Insgesamt 338 historische Vegetationsaufnahmen aus dem Zeitraum 1936-1969 vor der Intensivierung der Landwirtschaft wurden 2010/2011 mit vergleichbaren Methoden wiederholt. Dadurch wurde eine überregionale Bewertung des Vegetationswandels in den vergangenen 50-60 Jahren im Hinblick auf den regionalen Artenpool, die Artenzahl pro Aufnahmefläche, die relative Häufigkeit pflanzlicher Lebensformen und die Häufigkeit von Makrophyten-Gesellschaften möglich. Die frei schwimmenden Wuchsformtypen Lemniden und Ceratophylliden und Bestände, die dem Verband Nymphaeion (durch schwimmblattbildende Arten charakterisiert) zuzuordnen sind, nahmen zu. Die wesentlichen Verlierer sind Makrophytenbestände der Verbände Ranunculion und Potamogetonion (im Sediment wurzelnde Arten mit Unterwasserblättern), welche bei erhöhter Wassertrübung unter Lichtmangel leiden. Die Folge ist eine überregionale Homogenisierung und deutliche Verarmung der Makrophyten-Vegetation. Als wahrscheinliche Ursachen werden die hohen Nährstoffeinträge aus der Landwirtschaft und häufige Störung durch wasserbauliche Maßnahmen diskutiert. We investigated the long-term change in the macrophyte vegetation of running waters in the northwest German lowlands since the 1950s/60s in four study regions within the agricultural landscape (Ems-Hunte region, Lüneburg Heath with Aller lowlands, northern Harz foothills, eastern Holstein region). In 338 plots with historical vegetation relevés from the 1936-1969 period, sampling was repeated in 2010/2011 with comparable methods for analysing changes in the regional species pool of hydrophytic taxa, in plot-level species richness, and in the number of red-listed species. The size of the regional species pools of macrophyte taxa decreased by 27 % and plot-level diversity declined by 19 % on average. The most severe losses in frequency occurred in submerged rooted hydrophytes (Potamogetonion and Ranunculion alliances), probably due to increased water turbidity as a consequence of regular disturbance and decades of nutrient inputs. Free-floating growth forms (lemnids and ceratophyllids) increased in frequency in relative terms. River engineering and maintenance works are other stressors that certainly have reduced macrophyte diversity.

This resampling study in 338 semi-permanent plots analyses changes in river macrophyte diversity in 70 water courses (small streams to medium-sized rivers) from four regions of the northwest German lowlands during the last six decades. The total macrophyte species pool decreased between the 1950s and 2010/2011 by 28% (from 51 to 37 species), mean plot-level species richness by 19% (from 4.7 to 3.8 species per relevé) and the number of red-listed species by 40% (from 30 to 18 species). Species loss was associated with marked change in species traits: species with presumably higher mechanical stress tolerance (indicated by low specific leaf area and short leaf longevity) are more abundant today. Nearly, half of the species present in the 1950s had either disappeared or been replaced by other species in the recent relevés. The dramatic impoverishment is likely a consequence of continued nutrient input that drove oligo- and mesotraphent species to extinction, and of restructuring and maintenance works in the water courses that reduced stagnant and undisturbed river habitats, where stress-intolerant species can persist. Efficient measures to reduce the nutrient load and to re-naturalise stream and river beds are urgently needed to halt and reverse the loss of macrophyte diversity.

The mitochondrial inner membrane consists of two domains, inner boundary membrane and cristae membrane that are connected by crista junctions. Mitofilin/Fcj1 was reported to be involved in formation of crista junctions, however, different views exist on its function and possible partner proteins. We report that mitofilin plays a dual role. Mitofilin is part of a large inner membrane complex, and we identify five partner proteins as constituents of the mitochondrial inner membrane organizing system (MINOS) that is required for keeping cristae membranes connected to the inner boundary membrane. Additionally, mitofilin is coupled to the outer membrane and promotes protein import via the mitochondrial intermembrane space assembly pathway. Our findings indicate that mitofilin is a central component of MINOS and functions as a multifunctional regulator of mitochondrial architecture and protein biogenesis.

In Central Europe several plant species of dry grasslands are particularly rare. Here I investigate whether habitat requirements, reproduction, and dispersal potential can contribute to the rarity of Astragalus exscapus (Fabaceae) growing in dry grassland habitats in dry regions of Europe. In addition, I question whether historic events might have contributed to the present-day rarity of A. exscapus. To assess habitat requirements of A. exscapus, vegetation composition and soil characteristics were studied in 37 populations in central Germany. Production and dispersal potential of seeds were investigated in 10 populations, and germination and recruitment were assessed in experimental plots in three populations. Vegetation of the habitats included most dry grassland community types occurring in the central German dry region indicating a broad ecological niche of the species within dry subcontinental grasslands. Soil characteristics of the habitats also spanned a wide range. Seed production was moderate. 98% of the seeds sown in the laboratory germinated whereas under natural conditions 20% of the seeds developed seedlings. Half of these seedlings survived for one year but only 4.5% for two years. 90% of the seeds were dispersed less than 50 cm distance indicating a low dispersal potential. I conclude that A. exscapus is mainly limited in dispersal but recruitment limitation might also be important in explaining its rarity. Furthermore, former climate change and postglacial reforestation of the area very likely contribute to the rarity of A. exscapus.

The Transylvanian Plateau in Romania is well known to host large areas of a variety of dry grassland types, still traditionally managed by low-intensity mowing or grazing. While this natural heritage is now under threat from changes in agricultural practices, the diversity of Transylvanian dry grasslands is still little understood. There is a lack of both field data sampled with standardised methods and a syntaxonomic treatment with modern statistical methods and supra-regional perspective. Therefore, the European Dry Grassland Group (EDGG) carried out its first international Research Expedition in Transylvania 2009 to study syntaxonomy, vegetation-environment relationships, and biodiversity patterns of these communities. In various locations across Transylvania, we sampled 10-m(2) vegetation plots (n = 82) and nested-plot series from 0.0001 m(2) to 100 m(2) (n = 20), including all vascular plant, bryophyte, and lichen species, as well as structural and soil data. The vegetation classification was carried out with modified TWINSPAN, followed by determination of diagnostic species with phi values and a small-scale re-assignment of releves with the aim of crispness maximisation. Both TWINSPAN and ordination revealed three major groups of syntaxa, which were matched to three orders from the class of basiphilous dry grasslands, Festuco-Brometea, represented by one alliance each: rocky dry grasslands (Stipo pulcherrimae-Festucetalia pallentis: Seslerion rigidae); xeric grasslands on deep soils (Festucetalia valesiacae: Stipion lessingianae) and meso-xeric grasslands on deep soils (Brachypodietalia pinnati: Cirsio-Brachypodion pinnati). We accepted nine association-level units plus two that potentially merit association status but were only represented by one releve each. Most of the units could be identified with one or several previously described associations. To support nomenclatural stability, we provide a nomenclatural revision and designate nomenclatural types where previously there were none. Further, we used DCA ordination and analysis of variance to determine the main environmental drivers of floristic differentiation and to determine ecological and structural differences between the vegetation types. The strongest differentiation occurred along the aridity gradient with the dense, particularly diverse stands on more or less level sites on the one hand (Brachypodietalia pinnati) and the more open, less diverse stands on steep south-facing slopes on the other end of the gradient (Stipo pulcherrimae-Festucetalia pallentis, Festucetalia valesiacae). The two xeric orders were then separated along the second DCA axis, with the Stipo pulcherrimae-Festucetalia pallentis inhabiting the stone-rich sites at higher altitudes while the Festucetalia valesiacae occur on soft, deep substrata at lower altitudes. The analysed dry grassland communities have extraordinarily high a-diversity at all spatial scales for all plants and for vascular plants, but are relatively poor in bryophytes and lichens. Some formerly mown stands of the Festuco sulcatae-Brachypodietum pinnati (Brachypodietalia pinnati) are even richer in vascular plant species than any other recorded vegetation type worldwide on the spatial scales of 0.1 m(2) (43) and 10 m(2) (98); the respective releves are documented here for the first time. Also, the beta-diversity of the grasslands was unexpectedly high, with a mean z-value of 0.275. Despite its limited extent, the methodological thoroughness of this study allows us to shed new light on the syntaxonomy of dry grasslands in Romania and to raise the awareness that Transylvania still hosts High Nature Value grasslands that are biodiversity hotspots at a global scale but at the same time are highly endangered through changes in agricultural practices.

Question Did vegetation of former coppice‐with‐standards woodlands, which were in conversion towards high forest for about 100 yrs, change over the last 41 yrs (1970–2011)? What were the main drivers of vegetation change? Location Dransfeld Plateau, central Germany. Methods Repetition of 85 historical semi‐permanent vegetation plots located in 13 forest patches on limestone soil. Differences in species composition and plant functional types between historical and recent plots were analysed using a block multi‐response permutation procedure (bMRPP), NMDS, indicator species analysis (ISA) and ANOVA. Results We found significant changes in all vegetation layers. In the tree layer, Fagus sylvatica and Hedera helix had increased, while Quercus robur and Carpinus betulus had decreased. In the understorey, tree regeneration had strongly increased. In the herbaceous layer, species richness had decreased from 30 to 24 species per 100 m², and the abundance of plant functional types had changed: the proportion of geophytes and therophytes had increased, while the proportion of hemicryptophytes had decreased. Spring‐green species (i.e. species active mainly before tree foliation) had increased, while summer‐green species had decreased. In addition, the estimated mean SLA of herbaceous species had increased. The proportion of closed‐forest species had slightly increased, while the proportion of species of forest edges and clearings had decreased. NMDS ordination separated the herbaceous layers from 1970 and 2011 along the second axis, which correlated with the indicator values for continentality (decrease over time) and N (increase over time). Conclusions Although the stands still shared many characteristics of coppice‐with‐standards woodlands, the vegetation had clearly shifted towards that of darker and more nutrient‐rich forest. This indicates both a marked legacy of historic coppice management and a strong influence of recent high forest management, as well as N deposition.

The region of Southern Transylvania in Romania contains large expanses of species-rich grassland and mixed farmland. Within these landscapes, clusters of small, steep-sided slumping hills support mosaics of herbaceous vegetation caused by the heterogeneity in temperature and water supply and maintained by mowing or grazing. These are of conservation interest not only for the high species density, but also the relict steppe-like vegetation types especially found on their south-facing slopes. Usually surrounded by more intensively used mesic grassland, these hills can be considered patches of species-rich grassland vegetation. We therefore surveyed the vascular plants in 10 m(2) plots on the south- and north-facing slopes of 50 hills in 12 clusters in order to investigate the influence of their size and isolation on the species richness and composition of the vegetation. We found that larger hills had higher plot-scale species richness, a greater proportion of competitive species and a lower proportion of species of steppe-like vegetation, but only on their south-facing slopes where the conditions are more extreme. Both large and small hills should be considered as important habitats and potential sources of propagules for plant communities in the surrounding areas.

The mitochondrial inner membrane plays central roles in bioenergetics and metabolism and contains several established membrane protein complexes. Here, we report the identification of a mega-complex of the inner membrane, termed mitochondrial multifunctional assembly (MIMAS). Its large size of 3 MDa explains why MIMAS has escaped detection in the analysis of mitochondria so far. MIMAS combines proteins of diverse functions from respiratory chain assembly to metabolite transport, dehydrogenases, and lipid biosynthesis but not the large established supercomplexes of the respiratory chain, ATP synthase, or prohibitin scaffold. MIMAS integrity depends on the non-bilayer phospholipid phosphatidylethanolamine, in contrast to respiratory supercomplexes whose stability depends on cardiolipin. Our findings suggest that MIMAS forms a protein-lipid mega-assembly in the mitochondrial inner membrane that integrates respiratory biogenesis and metabolic processes in a multifunctional platform.

Hepatocellular carcinoma (HCC) is one of the most frequent tumors worldwide with rising incidence. The inflammatory cytokine, interleukin-6 (IL-6), is a critical mediator of HCC development. It can signal through two distinct pathways: the IL-6 classic and the IL-6 trans-signaling pathway. Whereas IL-6 classic signaling is important for innate and acquired immunity, IL-6 trans-signaling has been linked to accelerated liver regeneration and several chronic inflammatory pathologies. However, its implication in liver tumorigenesis has not been addressed yet. Here, we show that IL-6 trans-signaling, but not IL-6 classic signaling, is essential to promote hepatocellular carcinogenesis by two mechanisms: First, it prevents DNA-damage-induced hepatocyte apoptosis through suppression of p53 and enhances β-catenin activation and tumor proliferation. Second, IL-6 trans-signaling directly induces endothelial cell proliferation to promote tumor angiogenesis. Consequently, soluble gp130 fused to Fc transgenic mice lacking IL-6 trans-signaling are largely protected from tumor formation in a diethylnitrosamine/3,3',5,5'-tetrachloro-1,4-bis(pyridyloxy)benzene model of HCC.CONCLUSION:IL-6 trans-signaling, and not IL-6 classic signaling, is mandatory for development of hepatocellular carcinogenesis. Therefore, specific inhibition of IL-6 trans-signaling, rather than total inhibition of IL-6 signaling, is sufficient to blunt tumor initiation and impair tumor progression without compromising IL-6 classic signaling-driven protective immune responses. (Hepatology 2017;65:89-103).