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61.
Jonas Kuppler Ccile H. Albert Gregory M. Ames William Scott Armbruster Gerhard Boenisch Florian C. Boucher Diane R. Campbell Liedson T. Carneiro Eduardo Chacn‐Madrigal Brian J. Enquist Carlos R. Fonseca Jos M. Gmez Antoine Guisan Pedro Higuchi Dirk N. Karger Jens Kattge Michael Kleyer Nathan J. B. Kraft Anne‐Amlie C. Larue‐Konti Amparo Lzaro Martin Lechleitner Deirdre Loughnan Vanessa Minden Ülo Niinemets Gerhard E. Overbeck Amy L. Parachnowitsch Francisco Perfectti Valrio D. Pillar David Schellenberger Costa Nina Sletvold Martina Stang Isabel Alves‐dos‐Santos Helena Streit Justin Wright Marcin Zych Robert R. Junker 《Global Ecology and Biogeography》2020,29(6):992-1007
62.
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ER Carbonero AC Ruthes CS Freitas P Utrilla J Gálvez EV Silva GL Sassaki PA Gorin M Iacomini 《Carbohydrate polymers》2012,90(2):814-819
Hot aqueous extraction of the basidiocarps of the mushroom Pleurotus sajor-caju provided a cold water-soluble, gel-like glucan, which was characterized chemically, and its effects on RAW 264.7 cell line (mouse leukaemic monocyte macrophage) activation were determined. NMR spectroscopy, HPSEC, methylation analysis, and a controlled Smith degradation showed it to have a branched structure with a (1→3)-linked β-Glcp main-chain, substituted at O-6 by single-unit β-Glcp side-chains, on the average of two to every third residues of the backbone, with a molar mass of 9.75×10(5)gmol(-1). In macrophage cell culture, the β-glucan induced production of NO and the cytokines TNF-α, IL-1β, these effects being very similar as those of Escherichia coli serotype 0111:B4 Sigma-Aldrich lipopolysaccharide (LPS), although not modifying the response of LPS-activated macrophages. The results suggest that the (1→3), (1→6)-linked β-glucan from P. sajor-caju may have potential for immunological activities, although additional experiments are necessary for a better understanding of the mechanisms involved. 相似文献
64.
Vegetation mosaics of grassland/savanna and forest can be found in tropical and subtropical regions of the world, as in southern Brazil, where climate conditions are suitable for forest. Changes in intensity or frequency of disturbances could enable woody species encroachment in grassland communities; however, the processes are related to site conditions and life history of pioneer species. In this paper, we study transition patterns of forest to grassland in the absence of grazing, but under different site conditions related to aspect (landscape position) and time since the last burn. Data are based on shrub and tree species composition and soil variables at forest–grassland boundaries. We found 119 woody species of 42 families along transects of 27 m into the forest and 31.5 m into the grassland. Gradients from forest to grassland were analysed as compositional trajectories in ordination space and differences in the spatial patterns depicted between distinct site aspects. The time since the last fire did not influence these patterns. Inside the forest, tree species diversity was significantly higher close to the edge, independent of the density of individuals. Two main mechanisms may promote forest expansion into the grassland. First, a gradual tree encroachment near the edge and, second, a mechanism linked to the recruitment of isolated pioneer trees within the grassland matrix, most frequently near rocky outcrops, where a decrease in grass biomass leads to low-intensity fires. Despite vegetation patterns at boundaries differing according to aspect, the most important explanatory factor was the distance from the forest border, not just by itself, but with all correlated parameters that are changing along the gradient. 相似文献
65.
66.
Traits of dominant plant species drive normalized difference vegetation index in grasslands globally
Thore Engel Helge Bruelheide Daniela Hoss Francesco M. Sabatini Jan Altman Mohammed A. S. Arfin-Khan Erwin Bergmeier Tomáš Černý Milan Chytrý Matteo Dainese Jürgen Dengler Jiri Dolezal Richard Field Felícia M. Fischer Dries Huygens Ute Jandt Florian Jansen Anke Jentsch Dirk N. Karger Jens Kattge Jonathan Lenoir Frederic Lens Jaqueline Loos Ülo Niinemets Gerhard E. Overbeck Wim A. Ozinga Josep Penuelas Gwendolyn Peyre Oliver Phillips Peter B. Reich Christine Römermann Brody Sandel Marco Schmidt Franziska Schrodt Eduardo Velez-Martin Cyrille Violle Valério Pillar 《Global Ecology and Biogeography》2023,32(5):695-706
Aim
Theoretical, experimental and observational studies have shown that biodiversity–ecosystem functioning (BEF) relationships are influenced by functional community structure through two mutually non-exclusive mechanisms: (1) the dominance effect (which relates to the traits of the dominant species); and (2) the niche partitioning effect [which relates to functional diversity (FD)]. Although both mechanisms have been studied in plant communities and experiments at small spatial extents, it remains unclear whether evidence from small-extent case studies translates into a generalizable macroecological pattern. Here, we evaluate dominance and niche partitioning effects simultaneously in grassland systems world-wide.Location
Two thousand nine hundred and forty-one grassland plots globally.Time period
2000–2014.Major taxa studied
Vascular plants.Methods
We obtained plot-based data on functional community structure from the global vegetation plot database “sPlot”, which combines species composition with plant trait data from the “TRY” database. We used data on the community-weighted mean (CWM) and FD for 18 ecologically relevant plant traits. As an indicator of primary productivity, we extracted the satellite-derived normalized difference vegetation index (NDVI) from MODIS. Using generalized additive models and deviation partitioning, we estimated the contributions of trait CWM and FD to the variation in annual maximum NDVI, while controlling for climatic variables and spatial structure.Results
Grassland communities dominated by relatively tall species with acquisitive traits had higher NDVI values, suggesting the prevalence of dominance effects for BEF relationships. We found no support for niche partitioning for the functional traits analysed, because NDVI remained unaffected by FD. Most of the predictive power of traits was shared by climatic predictors and spatial coordinates. This highlights the importance of community assembly processes for BEF relationships in natural communities.Main conclusions
Our analysis provides empirical evidence that plant functional community structure and global patterns in primary productivity are linked through the resource economics and size traits of the dominant species. This is an important test of the hypotheses underlying BEF relationships at the global scale. 相似文献67.
Abstract. Hypothesis testing in phytocoenological applications is likely to be hindered when based on conventional statistical methods. The problem created by unrealistic assumptions can, however, be overcome by randomization. This paper discusses the general idea of randomization testing, describes a method and interprets its application in group comparisons. Two sets of variables are involved, the vegetation set on the basis of which the groups are compared and the environmental factors which delimit the groups under different analytical designs. Although simple partitioning of sum of squares is at the core of the test, the method has versatility of testing uni- or multifactor designs, which is novel in phytocoenological applications. The algorithm has been implemented in programs SYNCSA and MULTIV by V.P. Data from the Campos of southern Brazil are used for illustration. 相似文献
68.
Expression of the "split gene" cob in yeast mtDNA. Nuclear mutations specifically block the excision of different introns from its primary transcript 总被引:12,自引:0,他引:12
T Pillar B F Lang I Steinberger B Vogt F Kaudewitz 《The Journal of biological chemistry》1983,258(13):7954-7959
Five nuclear mutants falling into five different complementation groups are shown to block the maturation of long form mitochondrial cob RNA at five different processing steps. At the same time they prevent complete processing of the oxi 3 RNA, thus exhibiting the same phenotype as mitochondrial box mutants (cyt b- and oxi 3-). The different nuclear factors in question have varying ranges of specificity for the removal of introns from cob RNA, from only one to at the most three introns. Two mutated nuclear elements are shown to be specific for the processing of introns present only in the long form cob gene. One such mutation shows, as expected, no deleterious effect on the processing of the short form cob RNA exchanged into the mutant via cytoduction. The role of nuclear coded factors in the possible translation or activity of introncoded products ("maturases") is discussed for two mutants. Striking parallels are found between diverse polypeptide products, presumably translated from accumulated cob RNA intermediates, in pet- and mit- mutants blocked in the excision of the same intron. 相似文献
69.
70.
G E Overbeck S C Müller V D Pillar J Pfadenhauer 《Revista brasleira de biologia》2006,66(4):1073-1090
In regularly burned grassland on Morro Santana, Porto Alegre, RS, Brazil, we investigated differences in the floristic composition and their relation to soil properties, aspect and distance from the forest border. In 48 plots of 0.75 m2, we identified a total of 201 species from a local species pool of approximately 450 to 500 species. Most species occurred in low frequencies, showing clumpy distribution patterns in the studied area. Multivariate analysis showed that plots close to the forest edge clearly differed from plots in the open grassland concerning composition and structure. Plots exposed to the north differed from plots on the top of the hill both in the composition of species as well as in soil variables, mainly due to shallower soil in the former. No strong relation between soil properties and variation in vegetation composition could be detected at a finer scale. The studied grassland, as all grassland vegetation in southern Brazil, is very rich in species compared to other grassland formations worldwide. However, this high biodiversity and conservational value of Campos vegetation in general has so far not been recognized properly. Disturbance is essential to maintain this open vegetation type and its species richness. Fire should be considered as a management option in the absence of grazing. 相似文献