Apomicts in the vegetation of Central Europe
- Summed frequency data of apomictic taxa derived from vegetation relevées from Central Europe were correlated with ecological traits – water content of soil, calcium and magnesium content of soil or water, nutrient content of soil or water, environmental dynamics, hemeroby, frequency of stress-tolerant species, salt tolerance, altitude, height, and frequency of annual taxa – of alliances of the Central Euro-pean vegetation. The partly problematic identification of taxa where apomixis is important for seed production was based on a literature review. In Central Europe, high altitudes favour apomictic taxa. Otherwise, no correlations between ecological factors attributed to the alliances of the European phyto-sociological system and frequencies of apomictic taxa in the alliances of the European phytosociological system were found. Analyses could not confirm theories on ecological preferences of apomictic taxa; e.g., that competition penalizes apomicts, apomicts have better colonizing abilities than sexual plants, or apomicts have larger ranges than their sexual relatives could not be confirmed.
Evidence for increasing homogenization and de-ruralization of the Central European village flora
- In this study, the spontaneous flora of North Rhine-Westphalian villages (NW Germany) recorded in the periods 1980–1984 and 2004–2005 was analyzed. We asked: (i) Did the similarity of the village flora increase with time and to what extent did non-native species contribute to this? (ii) Is the ongoing trend of urbanization reflected in the village flora? (iii) Regarding the species composition and β-diversity: are there differences between the results of a repeated survey and of a type comparison? In both periods, 200 villages were visited once, using consistent criteria for village selection and floristic investigation. Of these, a subset of 61 villages was investigated in both time periods and the rest were selected randomly for the second survey but with respect to the same criteria as used in the first. Using different β -diversity indices (Sørensen index of dissimilarity, Simpson index of dissimilarity and nest-edness resultant index) to disentangle pure species turnover and nestedness of species assemblages, we tested whether the similarity among the villages increased over the years. This was done by calculating all pairwise comparisons among the villages of each time period, i.e. their spatial turnover. Additional-ly, different ecological groups were defined (e.g. “neophytes”, “C-strategists” or “urbanophilous spe-cies”) using the subgroups of species traits (floristic status, Grime’s life strategy and urbanity) to inden-tify urbanization and compositional changes. Our results show that the traditional village flora (species of the Arction lappae, Bidention tripartitae and Potentillion anserinae) is further blurred towards un-specific ubiquitous assemblages found in the periphery of man and that the floristic urbanization is still ongoing. Supported by nearly all ecological groups regarded, our results corroborate that the species composition of Central European villages underwent a considerable degree of homogenization. To some extent this is caused by structural homogenization of villages. Regarding the considerable in-crease of common ubiquists and α-diversity in general, however, changes in weeding practices seem to be the main reason. Based on the re-investigated subset we could show that comparable results can be obtained by a consistent use of criteria for the selection of villages, even if unpaired samples were used.
What are the long-term effects of livestock grazing in steppic sandy grassland with high conservation value? Results from a 12-year field study
- To examine the necessity of livestock grazing for managing threatened sand vegetation so as to en-sure and develop its nature-conservation value, we investigated a grazing system in a model nature reserve (German upper Rhine valley) characterized by threatened steppic sandy grassland (Allio-Stipetum vegetation complex: Habitats Directive Annex I, priority type 6240, additionally Koelerion glaucae: priority type 6120). The area has been grazed by sheep and additionally by donkeys since late summer of the year 2000. We established ungrazed (Au) and grazed plots (Ag) in the Allio-Stipetum complex in a systematic grid-plot design before grazing impact started. We sampled phytosociological relevés yearly in the Au/Ag plots for 12 vegetation periods. Addi-tionally, we sampled relevés on former farmland adjacent to the Allio-Stipetum complex (systematic grid-plot design) over ten vegetation periods. These former fields (Fg) were integrated in the grazing system since the beginning of the study. A constancy table was produced for Au, Ag, Fg. To determine the portions of target species (Koelerio-Corynephoretea, Festuco-Brometea species) we calculated target-species ratios (proportion of target species in comparison with the total species number; qualita-tive or quantitative approach: TSRqual/quant). We tested the effects of grazing, year and interactions on structural and phytodiversity characteristics of the relevés by mixed linear models. The results of the long-term experiment confirmed significant beneficial effects of grazing on habi-tat-typical structure and phytodiversity: e. g. reduction of litter, support of species which are short in height (< 20 cm), reduction of taller species (> 50 cm), support of the diversity of all plant species, of non-graminoid herbs and of target plant species, reduction of Calamagrostis epigejos, positive effects on TSRqual and TSRquant values. Similar developments, e.g. for phytodiversity and Calamagrostis epigejos cover, were observed on the former fields, but there are still seed limitations and high ruderal-plant dominances. In general TSRqual/quant show remarkable increases, but do not reach the values of the Ag plots. Concerning aims of nature conservation, the habitat-typical vegetation structure and phytodiversity of the Allio-Stipetum shows an excellent development as a consequence of the used grazing manage-ment. However, occasionally small populations of target species did not increase (e.g. Koeleria glauca). The former fields show a development towards valuable sandy grassland.
Plant communities and environmental gradients in mires of the Ammergauer Alps (Bavaria, Germany)
- In this study we present the plant communities, their abiotic site conditions and the main environ-mental gradients underlying variation in species composition of mire sites in three montane mires in the Northern Limestone Alps. For the phytosociological description of the mires we sampled species com-position in 115 relevés. In order to characterize the site conditions of the most important plant commu-nities we measured humification as well as water table depth, pH and electrical conductivity at 46 sites during a large part of the growing season. The main environmental gradients were identified by fitting environmental vectors and smoothed surfaces onto NMDS ordination. The most frequent communities on subneutral and neutral sites were the Caricetum davallianae, the Amblystegio stellati-Caricetum dioicae and the Schoenetum ferruginei, whereas acidic sites were mainly covered by the Eriophoro-Trichophoretum cespitosi. The most important factor for floristic variation between sites was pH. How-ever, within bogs and fens, variation in species composition was mainly due to differences in water table depth.
Spatial and temporal patterns of Ellenberg nutrient values in forests of Germany and adjacent regions - a survey based on phytosociological databases
- Within the last 30 years the role of nitrogen in Central European forests has changed fundamentally from limiting resource to environmental problem. As the retrospective tracking of nutrient availability by soil chemical and biogeochemical measurements faces serious problems, bioindication based on understorey species composition is indispensable for monitoring broad-scale eutrophication. Based on a broad survey of more than 100,000 forest vegetation plots accessible in electronic data-bases from Germany and adjacent countries, we calculated unweighted average Ellenberg nutrient values (mN) as a proxy of plant-available macronutrients. Based on the quantiles of the frequency distribution of mN in a regionally stratified sample, we define five trophic classes, which can be used to compare dimensionless mN values. We studied spatial patterns of average nutrient values within 17 regions and compared the periods from 1899 to 1975 and 1976 to 2006. After 1975 eutrophic (mN > 5.67) and hypertrophic (mN > 6.28) conditions were common everywhere except in the Alps and Saxony-Anhalt, but very oligotrophic conditions (mN < 3.44) were still widespread in regions with nutrient-poor bedrock. Before 1975 mN of plots had been lower than after 1975 in all but the southeastern regions. Between the pre- and post-1975 data the proportion of hypertrophic plots increased from 5.7 to 11.8%, and that of very oligo-trophic plots decreased from 14.6 to 8.3%. To remove bias resulting from uneven distribution, the dataset was stratified by five tree layer dom-inance types, period and region and resampled. In pre-1975 plots medians of mN increased in the order Pinus sylvestris, Quercus spp., Picea abies, Fagus sylvatica and Alnus spp, whereas the increase of mN was highest in forest types with historically low nutrient values. Therefore, the widespread change in mN must be attributed to the pronounced vegetation changes in Quercus and Pinus stands, indicating the importance of land-use change, i.e. recovery of nutrient cycles after hundreds of years of exploita-tion through coppicing, grazing and litter use. The analysis confirms eutrophication as a megatrend of modern vegetation change and demonstrates the high research potential of linking vegetation plot databases across large regions.
Breaking new ground? : On the achievements and shortcomings of a franco german perspective on the interwar period - Democracies and Totalitarian Regimes in the Interwar Period ; Part 6
Species differences in bacterial NhaA Na+/H+ exchangers
- Bacteria have adapted their NhaA Na(+)/H(+) exchangers responsible for salt homeostasis to their different habitats. We present an electrophysiological and kinetic analysis of NhaA from Helicobacter pylori and compare it to the previously investigated exchangers from Escherichia coli and Salmonella typhimurium. Properties of all three transporters are described by a simple model using a single binding site for H(+) and Na(+). We show that H.pylori NhaA only has a small acidic shift of its pH-dependent activity profile compared to the other transporters and discuss why a more drastic change in its pH activity profile is not physiologically required.
Targeting survivin in cancer: novel drug development approaches
- Survivin is a well-established target in experimental cancer therapy. The molecule is over-expressed in most human tumors, but hardly detectable in normal tissues. Multiple functions in different subcellular compartments have been assigned. It participates in the control of cell division, apoptosis, the cellular stress response, and also in the regulation of cell migration and metastasis. Survivin expression has been recognized as a biomarker: high expression indicates an unfavorable prognosis and resistance to chemotherapeutic agents and radiation treatment. Survivin is an unconventional drug target and several indirect approaches have been exploited to affect its function and the phenotype of survivin-expressing cells. Interference with the expression of the survivin gene, the utilization of its messenger RNA, the intracellular localization, the interaction with binding partners, the stability of the survivin protein, and the induction of survivin-specific immune responses have been taken into consideration. A direct strategy to inhibit survivin has been based on the identification of a specifically interacting peptide. This peptide can recognize survivin intracellularly and cause the degradation of the ligand–survivin complex. Technology is being developed that might allow the derivation of small molecular-weight, drug-like compounds that are functionally equivalent to the peptide ligand.
Fiscal consolidation strategy : [Version June 12, 2012]
John F. Cogan
John B. Taylor
Maik Hendrik Wolters
- In the aftermath of the global financial crisis and great recession, many countries face substantial deficits and growing debts. In the United States, federal government outlays as a ratio to GDP rose substantially from about 19.5 percent before the crisis to over 24 percent after the crisis. In this paper we consider a fiscal consolidation strategy that brings the budget to balance by gradually reducing this spending ratio over time to the level that prevailed prior to the crisis. A crucial issue is the impact of such a consolidation strategy on the economy. We use structural macroeconomic models to estimate this impact. We consider two types of dynamic stochastic general equilibrium models: a neoclassical growth model and more complicated models with price and wage rigidities and adjustment costs. We separate out the impact of reductions in government purchases and transfers, and we allow for a reduction in both distortionary taxes and government debt relative to the baseline of no consolidation. According to the initial model simulations GDP rises in the short run upon announcement and implementation of this fiscal consolidation strategy and remains higher than the baseline in the long run.
Bibliographical references on the bryophyte flora of the Canary Islands (1740-2006)
Gerard M. Dirkse
- A compilation of 427 bibliographical references on bryophytes from Canary Islands is presented. In order to include all the information dealing with Canarian bryoflora, we have listed all references that record any data on this subject.