Global Trends of Benthic Bacterial Diversity and Community Composition Along Organic Enrichment Gradients of Salmon Farms.
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ABSTRACT:
SUBMITTER: Fruhe L
PROVIDER: S-EPMC8116884 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Salinization is recognized as a threat to soil fertility worldwide. A challenge in understanding the effects of salinity on soil microbial communities is the fact that it can be difficult to disentangle the effects of salinity from those of other variables that may co-vary with salinity. Here we use a trait-based approach to identify direct effects of salinity on soil bacterial communities across two salinity gradients. Through dose-response relationships between salinity and bacterial growth, we quantified distributions of the trait salt tolerance within the communities. Community salt tolerance was closely correlated with soil salinity, indicating a strong filtering effect of salinity on the bacterial communities. Accompanying the increases in salt tolerance were consistent shifts in bacterial community composition. We identified specific bacterial taxa that increased in relative abundances with community salt tolerance, which could be used as bioindicators for high community salt tolerance. A strong filtering effect was also observed for pH across the gradients, with pH tolerance of bacterial communities correlated to soil pH. We propose phenotypic trait distributions aggregated at the community level as a useful approach to study the role of environmental factors as filters of microbial community composition.
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Project description:Saudi Arabia is mostly barren except the southwestern highlands that are susceptible to environmental changes, a hotspot for biodiversity, but poorly studied for microbial diversity and composition. In this study, 454-pyrosequencing of 16S rRNA gene hypervariable region V6 was used to analyze soil bacterial community along elevation gradients of the southwestern highlands.In general, lower percentage of total soil organic matter (SOM) and nitrogen were detected in the analyzed soil samples. Total 33 different phyla were identified across the samples, including dominant phyla Proteobacteria, Actinobacteria and Acidobacteria. Representative OTUs were grouped into 329 and 508 different taxa at family and genus level taxonomic classification, respectively. The identified OTUs unique to each sample were very low irrespective of the altitude. Jackknifed principal coordinates analysis (PCoA) revealed, overall differences in the bacterial community were more related to the quantity of specific OTUs than to their diversity among the studied samples.Bacterial diversity and soil physicochemical properties did not show consistent changes along the elevation gradients. The large number of OTUs shared between the studied samples suggest the presence of a core soil bacterial community in the southwestern highlands of Saudi Arabia.
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Project description:BackgroundThe elongating maize internode represents a useful system for following development of cell walls in vegetative cells in the Poaceae family. Elongating internodes can be divided into four developmental zones, namely the basal intercalary meristem, above which are found the elongation, transition and maturation zones. Cells in the basal meristem and elongation zones contain mainly primary walls, while secondary cell wall deposition accelerates in the transition zone and predominates in the maturation zone.ResultsThe major wall components cellulose, lignin and glucuronoarabinoxylan (GAX) increased without any abrupt changes across the elongation, transition and maturation zones, although GAX appeared to increase more between the elongation and transition zones. Microarray analyses show that transcript abundance of key glycosyl transferase genes known to be involved in wall synthesis or re-modelling did not match the increases in cellulose, GAX and lignin. Rather, transcript levels of many of these genes were low in the meristematic and elongation zones, quickly increased to maximal levels in the transition zone and lower sections of the maturation zone, and generally decreased in the upper maturation zone sections. Genes with transcript profiles showing this pattern included secondary cell wall CesA genes, GT43 genes, some β-expansins, UDP-Xylose synthase and UDP-Glucose pyrophosphorylase, some xyloglucan endotransglycosylases/hydrolases, genes involved in monolignol biosynthesis, and NAM and MYB transcription factor genes.ConclusionsThe data indicated that the enzymic products of genes involved in cell wall synthesis and modification remain active right along the maturation zone of elongating maize internodes, despite the fact that corresponding transcript levels peak earlier, near or in the transition zone.
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Project description:BackgroundI examined age patterns and the role of shifting educational distributions in driving trends in educational gradients in life expectancy among non-Hispanic Whites between 1991 and 2005.MethodsData were from the 1986-2004 National Health Interview Survey with mortality follow-up through 2006. Life expectancies were computed by sex, period and education. Age decompositions of life expectancy gradients and composition-adjusted life expectancies were computed to account for age patterns and shifting educational distributions.ResultsLife expectancy at age 25 among White men increased for all education groups, decreased among the least-educated White women and increased among White women with college degrees. Much of the decline in measured life expectancy for White women with less than a high school education comes from the 85+ age group. Educational gradients in life expectancy widened for White men and women. One-third of the gradient is due to ages below 50. Approximately 26% (0.7 years) and 87% (0.8 years) of the widening of the gradient in life expectancy between ages 25 and 85 for White women and men is attributable to shifting education distributions. Over half of the decline in temporary life expectancy among the least-educated White women is due to compositional change.ConclusionsLife expectancy has increased among White men for all education groups and has decreased among White women with less than a high school education, though not to the extent reported in previous studies. The fact that a large proportion of the change in education-specific life expectancy among women is due to the 85+ age group suggests changes in institutionalization may be affecting estimates. Much of the change in education-specific life expectancy and the growth in the educational gradient in life expectancy is due to the shifting distribution of individuals across education categories.
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Project description:Terrestrial herbs are important elements of tropical forests; however, there is a lack of research on their diversity patterns and how they respond to different intensities of forest-use. The aim of this study was to analyze the diversity of herbaceous angiosperms along gradients of elevation (50 m to 3500 m) and forest-use intensity on the eastern slopes of the Cofre de Perote, Veracruz, Mexico. We recorded the occurrence of all herbaceous angiosperm species within 120 plots of 20 m x 20 m each. The plots were located at eight study locations separated by ~500 m in elevation and within three different habitats that differ in forest-use intensity: old-growth, degraded, and secondary forest. We analyzed species richness and floristic composition of herb communities among different elevations and habitats. Of the 264 plant species recorded, 31 are endemic to Mexico. Both ?- and ?-diversity display a hump-shaped relation to elevation peaking at 2500 m and 3000 m, respectively. The relative contribution of between-habitat ?-diversity to ?-diversity also showed a unimodal hump whereas within-habitat ?-diversity declined with elevation. Forest-use intensity did not affect ?-diversity, but ?-diversity was high between old-growth and secondary forests. Overall, ?-diversity peaked at 2500 m (72 species), driven mainly by high within- and among-habitat ?-diversity. We infer that this belt is highly sensitive to anthropogenic disturbance and forest-use intensification. At 3100 m, high ?-diversity (50 species) was driven by high ?- and within-habitat ?-diversity. There, losing a specific forest area might be compensated if similar assemblages occur in nearby areas. The high ?-diversity and endemism suggest that mixes of different habitats are needed to sustain high ?-richness of terrestrial herbs along this elevational gradient.
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Project description:Abstract Despite many studies showing biodiversity responses to warming, the generality of such responses across taxonomic groups remains unclear. Very few studies have tested for evidence of bryophyte community responses to warming, even though bryophytes are major contributors to diversity and functioning in many ecosystems. Here, we report an empirical study comparing long‐term change in bryophyte and vascular plant communities in two sites with contrasting long‐term warming trends, using “legacy” botanical records as a baseline for comparison with contemporary resurveys. We hypothesized that ecological changes would be greater in sites with a stronger warming trend and that vascular plant communities, with narrower climatic niches, would be more sensitive than bryophyte communities to climate warming. For each taxonomic group in each site, we quantified the magnitude of changes in species' distributions along the elevation gradient, species richness, and community composition. We found contrasted temporal changes in bryophyte vs. vascular plant communities, which only partially supported the warming hypothesis. In the area with a stronger warming trend, we found a significant increase in local diversity and dissimilarity (β‐diversity) for vascular plants, but not for bryophytes. Presence–absence data did not provide sufficient power to detect elevational shifts in species distributions. The patterns observed for bryophytes are in accordance with recent literature showing that local diversity can remain unchanged despite strong changes in composition. Regardless of whether one taxon is systematically more or less sensitive to environmental change than another, our results suggest that vascular plants cannot be used as a surrogate for bryophytes in terms of predicting the nature and magnitude of responses to warming. Thus, to assess overall biodiversity responses to global change, abundance data from different taxonomic groups and different community properties need to be synthesized. We report an empirical study comparing long‐term change of bryophyte and vascular plant communities in two forest sites with contrasting long‐term warming trends, using resurvey data. We hypothesized that ecological changes would be greater in sites with a stronger warming trend, and that vascular plant communities, with narrower climatic niches, would be more sensitive than bryophyte communities to climate warming. We found a contrasted pattern of change, in the area with a stronger warming trend, we found a significant increase of local diversity and beta‐diversity for vascular plant, but not for bryophytes and presence‐absence data fail to detect shift in species distributions. The patterns observed for bryophytes support that local diversity can remain unchanged despite strong changes in composition. Our results suggest that vascular plants cannot be used as a surrogate for bryophytes in terms of predicting the direction and magnitude of responses to warming.
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