bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scaling hierarchy of factors controlling riparian vegetation patterns of the Fynbos Biome at the Western Cape, South Africa
Authors: Sieben E.J.J. , Mucina L. , Boucher C. 
Published: February 2009

AbstractQuestion: How can vegetation gradients be described in riparian zones located in a species‐rich mountain range and how do these gradients explain the variation found in the vegetation?Location: Hottentots Holland Mountains, Western Cape, South Africa.Methods: Three gradients (geographic, longitudinal, lateral) were defined to describe the complex vegetation patterns found here. The gradients are related as follows: (1) the geographic gradient: related to the climatic and topographical changes across the entire mountain range; (2) the longitudinal gradient related to the changes along the different river reaches; (3) the lateral gradient related to the processes along the profile of the riverbed. These three gradients operated on three different hierarchical levels. Partial Canonical Correspondence Analysis (pCCA) was used to determine the amount of variation that is explained on each of the hierarchical levels.Results: The geographical gradient explained the highest fraction (more than 50%) of the total variation explained. This can be ascribed to the high species turnover across landscapes in the Fynbos Biome; this is most likely an outcome that is specific for this region. The second most important gradient was the lateral gradient, which reflects stream power and inundation frequencies of the river. This gradient is represented by ca. 48% of the explained variation and this gradient explains the major disturbances occurring in a riverine ecosystem. The longitudinal gradient was the least important of the gradients and shows overlap with the geographical gradient.Conclusions: In the species‐rich environment of the Fynbos Biome geographical factors do not only account for variation in zonal vegetation but also for variation within azonal vegetation, like riparian corridors.
Positive density dependence in seedlings of the neotropical tree species Garcinia macrophylla and Xylopia micans
Authors: Anderson Jill T. 
Published: February 2009

AbstractQuestion: The Janzen‐Connell hypothesis predicts that herbivores and pathogens prevent seedlings from establishing in dense patches near adult conspecifics. Although many studies have investigated the Janzen‐Connell hypothesis, the environmental context – local or regional – in which juveniles establish is often overlooked. The objectives of this study were: (1) to evaluate Janzen‐Connell effects in contrasting environments, and (2) to incorporate microsite variation into the study of this hypothesis.Location: Pacaya‐Samiria Reserve, Peru.Methods: I assessed seedling performance of two tree species, Garcinia macrophylla and Xylopia micans, during one growing season. In an observational study, mortality and growth rates were regressed against distance to the nearest adult conspecific, conspecific seedling density, heterospecific plant density, and several abiotic variables in upland and floodplain forests. Field and shadehouse experiments were used to isolate distance‐ and density‐dependent effects.Results: Contrary to predictions, seedling survivorship increased in the presence of conspecific seedlings (Garcinia) and heterospecific understory plants (Garcinia and Xylopia) in the observational study. Survivorship in the field experiment, however, was unaffected by conspecific seedling density or adult proximity. In the shadehouse, Garcinia growth rates were highest in floodplain soils collected near adult conspecifics, but mortality was unrelated to the soil's habitat or proximity to an adult.Conclusions: The positive density dependence found in this study could have been produced by: (1) environmental factors that increase both density and survivorship, or (2) interspecific facilitation, if heterospecifics reduce herbivore or pathogen pressure on the focal species. Such interactions could help explain species coexistence in tropical forests.
Effects of water regime and habitat continuity on the plant species composition of floodplain forests
Authors: Glaeser Judith , Wulf Monika 
Published: February 2009

AbstractQuestions: 1. How big is the difference in the herbaceous layer composition between flooded and unflooded stands? 2. Are there species or species groups which have an affinity to ancient vs. recent forests in stands with different water regimes? 3. Are patterns of life history traits different between flooded and unflooded stands as well as between ancient and recent forests in stands with a different water regime?Location: Floodplain forests in the Middle Elbe region and district of Leipzig, Central Germany.Location: The herbaceous layer was studied in randomly selected quadrats of 9 m2 in 2000 and 2001. Six ancient (nplot=59) and six adjacent recent forests (nplot=108) were investigated in flooded stands as well as three ancient (nplot=41) and three recent forests (nplot=70) in stands that have not been flooded for 50 years. The association of single species, species groups and life history traits were statistically tested for flooded vs. unflooded stands and for ancient vs. recent forests.Results: Interruption of flooding caused a complete species turnover in the herbaceous layer composition. Whereas in the still flooded stands typical alluvial species prevail, species composition in stands without flooding for 50 years showed a closed relation to the Stellario‐Carpinetum. Six herbaceous species in the flooded and five in the unflooded stands showed a preference for ancient forests. Only one species in the flooded and six herbaceous species in the unflooded stands are significantly associated with recent forests. Life history traits differ between flooded and unflooded stands but are similar in ancient and recently flooded stands, while unflooded ancient forests have more geophytes and myrmecochorous species than recent forests.Conclusions: The specificity of species composition in floodplain forests can only be maintained by regular flooding. Interruption of inundations lead to differences in the patterns of species composition and life history traits between ancient and recent forests.
Wage Flexibility and Labour Market Institutions: A Meta‐Analysis
Authors: Clar Miquel , Dreger Christian , Ramos Raúl 
Published: February 2009

SUMMARYEvidence during the nineties about the response of real wages to shocks highlights that this response is substantially lower in European countries than in the United States and that there are important differences among European countries. Which are the reasons that explain these different reactions? In this paper, we apply meta‐analytical techniques in order to provide a quantitative summary of the available evidence regarding the influence of labour market institutions on real wage flexibility. We find that the design of the study affects the obtained results, and that in more deregulated labour markets with a lower presence of trade unions, this response is particularly larger.
Contrasting community responses to fertilization and the role of the competitive ability of dominant species
Authors: Liancourt P. , Viard‐Crétat F. , Michalet R. 
Published: February 2009

AbstractQuestion: Do contrasting biotic contexts in nutrient‐poor grasslands affect the predictability of invasion by exploitative species following fertilization?Location: French Alps.Methods: We examined community responses after 2 years of nutrient addition for two nutrient‐poor European calcareous grasslands, a mesoxeric community dominated by the short bunchgrass Bromus erectus and a mesic community dominated by the tall rhizomatous grass Brachypodium rupestre. We also performed reciprocal transplantations of these two dominant slow‐growing species and Arrhenatherum elatius, a tall fast‐growing grass that dominates nutrient‐rich communities and is likely to invade nutrient‐poor communities after fertilization. Transplants were grown with or without neighbors, in order to measure their individual responses (without neighbors) and competition intensity (by comparing performances with and without neighbors using the Relative Neighbor Effect index – RNE) during one growing season in all three communities.Results: In the Bromus community, fertilization induced a strong increase in fast‐growing grasses (including A. elatius). Competition intensity was low for the three transplanted grasses, but strongly increased with resource addition, to reach values observed in the Arrhenatherum community. In the Brachypodium community, no change in competition intensity with fertilization was detected, because of the high mortality of the two “non‐resident” species, irrespective of the presence of neighbors.Conclusions: Community responses to nutrient improvement are context‐dependent and vary as a function of the biotic environment. Soil processes are proposed as the main drivers of community resistance to the invasion of fast‐growing species in the mesic, nutrient‐poor grassland dominated by the large conservative competitor B. rupestre.
A California grasslands alkali specialist, Hemizonia pungens ssp. pungens, prefers non‐alkali soil
Authors: Veblen Kari E. , Young Truman P. 
Published: February 2009

AbstractQuestion: Edaphically severe habitats commonly support edaphic endemics, specialized plant species that do not occur elsewhere. The endemism of native plant species in edaphically specialized habitats suggests either (a) that these native endemic species are uniquely specialized to survive and grow better under the conditions prevalent in these harsh areas, or (b) that these areas represent refuges from competition with other (often exotic) species.Location: Central Valley, California, USA.Methods: We surveyed the vegetation distribution in alkali sinks and carried out a reciprocal transplant greenhouse experiment crossed with a competition treatment to examine the interplay between interspecific competition and edaphic factors in determining relative performance of an alkali endemic forb (Hemizonia pungens ssp. pungens) and its exotic grass competitor (Lolium multiflorum).Results: Lolium consistently performed better in non‐alkali soil. In contrast, Hemizonia, in the absence of competition, performed significantly better on the non‐alkali soils, but in competition with Lolium, performed equally well on alkali and non‐alkali soils.Conclusions: These results suggest that Hemizonia does not inherently prefer harsh alkali soil, but is better able to tolerate alkali soil and may be excluded from more moderate soils by competition. Therefore, edaphic and biotic effects may interact to determine the spatial distribution of this edaphic endemic. Our data suggest a mechanism by which competition between native and exotic species on impoverished soils leads to dominance of native species and creation of refugia for native species where exotic species are unable to thrive.
Relative climatic, edaphic and management controls of plant functional trait signatures
Authors: Pakeman Robin J. , Lepš Jan , Kleyer Michael , Lavorel Sandra , Garnier Eric ,   the VISTA consortium
Published: February 2009

AbstractObjective: To identify the relative roles of climatic, edaphic and management factors in controlling the weighted mean traits of vegetation.Location: Eleven sites in Europe and one in Israel undergoing transitions in land use.Material and Methods: Standardised methods were used to collect information on species traits and attributes from plots covering a range of land uses at each site. This was combined with abundance data to create a plot × trait matrix. Variance partitioning was used to identify the relative roles of climate, soil and management on the weighted and unweighted mean traits of the vegetation in the full data set, and the data set divided into vegetative traits (including life‐form, clonality, defence and a range of leaf traits) and traits linked to regeneration via seeds (including seed mass, dispersal and pollination mechanism).Results: Variance partitioning of the full data set showed that climate (18.7%), explained more variance in the weighted mean traits of the vegetation than climate and soil together (9.2), soil (6.9) and management (6.1). There was a similar distribution of variance explained for both vegetative and regeneration via seed traits, although more variance was explained for the latter. This restricted set of climatic, edaphic and management variables could explain 45‐50% of the variance in the weighted mean traits of the vegetation between plots. There were only small differences between analyses of the weighted and unweighted data.Conclusions: Despite large variations in climate and soils between sites, there was still a separate and recognisable impact of management on the mean weighted traits of the vegetation. There was also a degree of shared variation between the three groups of factors, indicating that the response of plant traits to one group of factors may not be predictable because they may be modulated by their response to other groups.
Seed size and response to rainfall patterns in annual grasslands: 16 years of permanent plot data
Authors: Peco B. , Rico L. , Azcárate F.M 
Published: February 2009

AbstractQuestion: Are seed size and plant size linked to species responses to inter‐annual variations in rainfall and rainfall distribution during the growing season in annual grasslands?Location: A 16‐year data set on species abundance in permanent plots 15 km north of Madrid in a Quercus ilex subsp. ballota dehesa.Methods: At species level, a GLM was used to analyse the effects of various rainfall indices (total autumn rainfall, early autumn rainfall and spring drought) on species abundance residuals with respect to time and topography. We also assessed the importance of seed size and plant size in the species responses at community level using species as data points. Seed mass and maximum stem length were used as surrogates for seed size and plant size, respectively.Results: Seed mass and plant size may explain some of the fluctuations in the floristic composition of annual species associated with autumn rainfall patterns. Species that are more abundant in dry autumns have greater seed mass than those species that are more abundant in wet autumns. Early autumn rainfall seems to favour larger plants.Conclusions: Our empirical results support the hypothesis that autumn rainfall patterns affect the relative establishment capacity of small and large seedlings in annual species.
Extinction debt in fragmented grasslands: paid or not?
Authors: Cousins Sara A.O. 
Published: February 2009

AbstractFragmentation of grasslands and forests is considered a major threat to biodiversity. In the case of plants, the effect of fragmentation or landscape context is still unclear and published results are divergent. One explanation for this divergence is the slow response of long‐lived plants, creating an extinction debt. However, this has not been empirically confirmed. In this study, data were compiled from broad‐scale studies of grasslands from throughout the world that relate plant diversity to fragmentation effects. Only seven studies from northern Europe, out of a total 61, gave any information on actual habitat fragmentation in time and space. In landscapes with >10% grassland remaining, present‐day species richness was related to past landscape or habitat pattern. In landscapes with <10% grassland remaining, in contrast, plant species richness was more related to contemporary landscape or habitat pattern. Studies from landscapes with >10% grassland remaining supported the concept of an extinction debt, while studies from more fragmented landscapes did not provide any evidence of an extinction debt. In order to make generalisations about historical legacies on species diversity in grasslands it is important to consider a range of highly transformed landscapes, and not only landscapes with a high amount of grassland remaining.
AMP‐activated protein kinase: a core signalling pathway in the heart
Authors: Kim A. S. , Miller E. J. , Young L. H. 
Published: February 2009

AbstractOver the past decade, AMP‐activated protein kinase (AMPK) has emerged as an important intracellular signalling pathway in the heart. Activated AMPK stimulates the production of ATP by regulating key steps in both glucose and fatty acid metabolism. It has an inhibitory effect on cardiac protein synthesis. AMPK also interacts with additional intracellular signalling pathways in a coordinated network that modulates essential cellular processes in the heart. Evidence is accumulating that AMPK may protect the heart from ischaemic injury and limit the development of cardiac myocyte hypertrophy to various stimuli. Heart AMPK is activated by hormones, cytokines and oral hypoglycaemic drugs that are used in the treatment of type 2 diabetes. The tumour suppressor LKB1 is the major regulator of AMPK activity, but additional upstream kinases and protein phosphatases also contribute. Mutations in the regulatory γ2 subunit of AMPK lead to an inherited syndrome of hypertrophic cardiomyopathy and ventricular pre‐excitation, which appears to be due to intracellular glycogen accumulation. Future research promises to elucidate the molecular mechanisms responsible for AMPK activation, novel downstream AMPK targets, and the therapeutic potential of targeting AMPK for the prevention and treatment of myocardial ischaemia or cardiac hypertrophy.
Language in Isolation, and Its Implications for Variation and Change
Authors: Schreier Daniel 
Published: February 2009

AbstractThis article discusses some approaches to the conceptualization of isolation in sociolinguistic research. It argues that isolation is a multifaceted phenomenon with geographic, social and attitudinal implications. Based on evidence from geographically isolated speech communities (mostly islands) and socially isolated ones (so‐calledSprachinseln) from around the world, it discusses their potential for variation and change studies, both in terms of synchrony (contact phenomena, language obsolescence or revival and intensification, language and identity, etc.) and diachrony, because they provide showcase scenarios to look into and reconstruct mechanisms of contact linguistics (e.g. new‐dialect formation), founder effects, colonial lag, etc.
A molecular key for building hyphae aggregates: the role of the newly identified Streptomyces protein HyaS
Authors: Koebsch Ilona , Overbeck Jens , Piepmeyer Sophie , Meschke Holger , Schrempf Hildgund 
Published: February 2009

SummaryStreptomycetes produce many metabolites with medical and biotechnological applications. During fermentations, their hyphae build aggregates, a process in which the newly identified protein HyaS plays an important role. The corresponding hyaS gene is present within all investigated Streptomyces species. Reporter fusions indicate that transcription of hyaS occurs within substrate hyphae of the Streptomyces lividans wild type (WT). The HyaS protein is dominantly associated with the substrate hyphae. The WT strain forms cylindrically shaped clumps of densely packed substrate hyphae, often fusing to higher aggregates (pellets), which remain stably associated during shaking. Investigations by electron microscopy suggest that HyaS induces tight fusion‐like contacts among substrate hyphae. In contrast, the pellets of the designed hyaS disruption mutant ΔH are irregular in shape, contain frequently outgrowing bunches of hyphae, and fuse less frequently. ΔH complemented with a plasmid carrying hyaS resembles the WT phenotype. Biochemical studies indicate that the C‐terminal region of HyaS has amine oxidase activity. Investigations of ΔH transformants, each carrying a specifically mutated gene, lead to the conclusion that the in situ oxidase activity correlates with the pellet‐inducing role of HyaS, and depends on the presence of certain histidine residues. Furthermore, the level of undecylprodigiosin, a red pigment with antibiotic activity, is influenced by the engineered hyaS subtype within a strain. These data present the first molecular basis for future manipulation of pellets, and concomitant production of secondary metabolites during biotechnological processes.
The thermodynamic landscape of methanogenic PAH degradation
Authors: Dolfing Jan , Xu Aiping , Gray Neil D. , Larter Stephen R. , Head Ian M. 
Published: February 2009

SummaryMethanogenic degradation of polycyclic aromatic hydrocarbons (PAHs) has long been considered impossible, but evidence in contaminated near surface environments and biodegrading petroleum reservoirs suggests that this is not necessarily the case. To evaluate the thermodynamic constraints on methanogenic PAH degradation we have estimated the Gibbs free energy values for naphthalene, phenanthrene, anthracene, pyrene and chrysene in the aqueous phase, and used these values to evaluate several possible routes whereby PAHs may be converted to methane. Under standard conditions (25°C, solutes at 1 M concentrations, and gases at 1 atm), methanogenic degradation of these PAHs yields between 209 and 331 kJ mol−1. Per mole of methane produced this is 27–35 kJ mol−1, indicating that PAH‐based methanogenesis is exergonic. We evaluated the energetics of three potential PAH degradation routes: oxidation to H2/CO2, complete conversion to acetate, or incomplete oxidation to H2 plus acetate. Depending on the in situ conditions the energetically most favourable pathway for the PAH‐degrading organisms is oxidation to H2/CO2 or conversion into acetate. These are not necessarily the pathways that prevail in the environment. This may be because the kinetic theory of optimal length of metabolic pathways suggests that PAH degraders may have evolved towards incomplete oxidation to acetate plus H2 as the optimal pathway.
Endurantism and the Psychological Approach to Personal Identity
Authors: BRUECKNER ANTHONY 
Published: February 2009

Abstract:This paper considers the question whether a psychological approach to personal identity can be formulated within an endurantist, as opposed to four‐dimensionalist, framework. Trenton Merricks has argued that this cannot be done. I argue to the contrary: a perfectly coherent endurantist version of the psychological approach can indeed be formulated.
Why We Should Lower Our Expectations about the Explanatory Gap
Authors: CAMPBELL NEIL 
Published: February 2009

Abstract:I argue that the explanatory gap is generated by factors consistent with the view that qualia are physical properties. I begin by considering the most plausible current approach to this issue based on recent work by Valerie Hardcastle and Clyde Hardin. Although their account of the source of the explanatory gap and our potential to close it is attractive, I argue that it is too speculative and philosophically problematic. I then argue that the explanatory gap should not concern physicalists because it makes excessive demands on physical theory.