| 1. |
- Abolfathi, Bela, et al.
(författare)
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The Fourteenth Data Release of the Sloan Digital Sky Survey : First Spectroscopic Data from the Extended Baryon Oscillation Spectroscopic Survey and from the Second Phase of the Apache Point Observatory Galactic Evolution Experiment
- 2018
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Ingår i: Astrophysical Journal Supplement Series. - : IOP Publishing Ltd. - 0067-0049 .- 1538-4365. ; 235:2
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Tidskriftsartikel (refereegranskat)abstract
- The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since 2014 July. This paper describes the second data release from this phase, and the 14th from SDSS overall (making this Data Release Fourteen or DR14). This release makes the data taken by SDSS-IV in its first two years of operation (2014-2016 July) public. Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey; the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data-driven machine-learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from the SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS web site (www.sdss.org) has been updated for this release and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020 and will be followed by SDSS-V.
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| 2. |
- Blanton, Michael R., et al.
(författare)
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Sloan Digital Sky Survey IV : Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
- 2017
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Ingår i: Astronomical Journal. - : IOP Publishing Ltd. - 0004-6256 .- 1538-3881. ; 154:1
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Tidskriftsartikel (refereegranskat)abstract
- We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and. high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially resolved spectroscopy for thousands of nearby galaxies (median z similar to 0.03). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between z similar to 0.6 and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGNs. and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5 m Sloan Foundation Telescope at the. Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5 m du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in 2016 July.
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| 3. |
- Householder, John Ethan, et al.
(författare)
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One sixth of Amazonian tree diversity is dependent on river floodplains
- 2024
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Ingår i: NATURE ECOLOGY & EVOLUTION. - 2397-334X.
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Tidskriftsartikel (refereegranskat)abstract
- Amazonia's floodplain system is the largest and most biodiverse on Earth. Although forests are crucial to the ecological integrity of floodplains, our understanding of their species composition and how this may differ from surrounding forest types is still far too limited, particularly as changing inundation regimes begin to reshape floodplain tree communities and the critical ecosystem functions they underpin. Here we address this gap by taking a spatially explicit look at Amazonia-wide patterns of tree-species turnover and ecological specialization of the region's floodplain forests. We show that the majority of Amazonian tree species can inhabit floodplains, and about a sixth of Amazonian tree diversity is ecologically specialized on floodplains. The degree of specialization in floodplain communities is driven by regional flood patterns, with the most compositionally differentiated floodplain forests located centrally within the fluvial network and contingent on the most extraordinary flood magnitudes regionally. Our results provide a spatially explicit view of ecological specialization of floodplain forest communities and expose the need for whole-basin hydrological integrity to protect the Amazon's tree diversity and its function.
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| 4. |
- Luize, Bruno Garcia, et al.
(författare)
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Geography and ecology shape the phylogenetic composition of Amazonian tree communities
- 2024
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Ingår i: JOURNAL OF BIOGEOGRAPHY. - 0305-0270 .- 1365-2699.
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Amazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types. Location: Amazonia. Taxon: Angiosperms (Magnoliids; Monocots; Eudicots). Methods: Data for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran's eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny. Results: In the terra firme and v & aacute;rzea forest types, the phylogenetic composition varies by geographic region, but the igap & oacute; and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R-2 = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R-2 = 28%). A greater number of lineages were significant indicators of geographic regions than forest types. Main Conclusion: Numerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions.
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| 5. |
- ter Steege, Hans, et al.
(författare)
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Mapping density, diversity and species-richness of the Amazon tree flora
- 2023
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Ingår i: COMMUNICATIONS BIOLOGY. - 2399-3642. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution. A study mapping the tree species richness in Amazonian forests shows that soil type exerts a strong effect on species richness, probably caused by the areas of these forest types. Cumulative water deficit, tree density and temperature seasonality affect species richness at a regional scale.
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| 6. |
- Albert, Séréna, 1992-
(författare)
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Benthic-pelagic coupling in a changing world : Structural and functional responses of microbenthic communities to organic matter settling
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Marine soft sediments form the second largest habitat on the planet. Organisms residing in this environment represent a vast reservoir of biodiversity, and play key roles in ecosystem processes. Most benthic organisms depend on organic matter (OM) inputs from phytoplankton in the overlying water column as food supply, but human impacts such as eutrophication and climate change are profoundly altering natural ecosystem dynamics. The consequences of changes in benthic-pelagic coupling for the biodiversity and functioning of soft-sediment communities have yet to be resolved. The aim of this thesis is to assess the role of OM settling on soft-sediments microeukaryotic (small organisms < 1 mm) and bacterial communities. The intents are two-fold, to investigate impacts on (1) community structure and diversity (chapters I, II and IV); and (2) ecosystem functioning, notably in relation to nitrogen (N) cycling (chapters I and III). Our results show that settling OM quantity and quality both had a significant impact on microeukaryotic alpha-diversity. We observed a decrease in alpha-diversity following settling of diatom-derived spring bloom OM, possibly as a result of competitive exclusion, while cyanobacteria-derived summer bloom OM did not affect alpha-diversity (chapters I and IV). We also found that high biomass of diatoms and others fast sinking phytoplankton groups in the water column led to lower microeukaryotic alpha diversity after this material settled on the seafloor (chapter IV). Presumably, following this large sedimentation event, sediment oxygen (O2) demand was strongly stimulated, excluding O2-sensitive taxa. Overall, we propose that the assembly of microeukaryotic communities was primarily mediated by OM settling quantity (chapter IV), while differences in OM quality led to significant but more subtle changes, occurring at fine taxonomic level (chapter I). The response of bacterial communities to OM settling was less pronounced, and probably restricted to the uppermost sediment layer (chapters I and IV). We did, however, observe a significant effect of OM quality on bacterial communities assembly at the sediment-water interface, with taxa favored either by diatom- or by cyanobacteria-derived OM (chapter II). This study also showed that feedback mechanisms from nutrient recycling in the sediment could play a role in this response. Finally, our results indicated a substantial influence of OM quality on N cycling at the sediment-water interface. We found that settling of fresh OM (i.e. low C:N ratio) stimulated denitrification activity (chapters I and III), while simultaneously promoting more N recycling to the water column than settling of degraded OM (i.e. high C:N ratio) did (chapter III). Altogether, our results indicate that current changes in OM settling dynamics in marine systems will likely impact microeukaryotic and, to some extent, bacterial biodiversity in soft sediments. Alterations in settling OM quality, in particular, may also affect crucial microbial processes involved in N cycling. This thesis highlights the importance of considering benthic-pelagic coupling mechanisms to better understand likely future changes in marine ecosystems.
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| 7. |
- Albert, Séréna, et al.
(författare)
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Influence of settling organic matter quantity and quality on benthic nitrogen cycling
- 2021
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Ingår i: Limnology and Oceanography. - : Wiley. - 1939-5590 .- 0024-3590. ; 66:5, s. 1882-1895
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Tidskriftsartikel (refereegranskat)abstract
- Coastal sediments are major contributors to global carbon (C) mineralization and nutrient cycling and are tightly linked to processes in the pelagic environment. In this study, we aimed to investigate the regulating potential of quantity and quality of planktonic organic matter (OM) deposition on benthic metabolism, with a particular focus on nitrogen (N) cycling processes. We simulated inputs of spring (C : N 10.9) and summer (C : N 5.6) plankton communities in high and low quantities to sediment cores, and followed oxygen consumption, nutrient fluxes as well as nitrate reduction rates, that is, denitrification and dissimilatory nitrate reduction to ammonium for 10 d. Our results demonstrate the primary importance of OM quality in determining the fate of organic N once it settles to the sediment surface. Settling of N-rich summer plankton material resulted in a ∼ twofold lower denitrification efficiency (40–56%) compared to N-poor spring plankton (88–115%). This indicates that N-rich plankton deposition favors recycling of inorganic nutrients to the water column over N-loss via denitrification. OM quantity was positively related to mineralization activity, but this neither directly affected N fluxes nor denitrification activity, highlighting the complex interplay between the OM quantity and quality in regulating N cycling. In light of these new findings, we support the use of simple qualitative indicators such as C : N ratio of OM to investigate how future changes in benthic-pelagic coupling might influence N budgets at the sediment–water interface.
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| 8. |
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| 9. |
- Albert, Séréna, et al.
(författare)
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Phytoplankton settling quality has a subtle but significant effect on sediment microeukaryotic and bacterial communities
- 2021
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- In coastal aphotic sediments, organic matter (OM) input from phytoplankton is the primary food resource for benthic organisms. Current observations from temperate ecosystems like the Baltic Sea report a decline in spring bloom diatoms, while summer cyanobacteria blooms are becoming more frequent and intense. These climate-driven changes in phytoplankton communities may in turn have important consequences for benthic biodiversity and ecosystem functions, but such questions are not yet sufficiently explored experimentally. Here, in a 4-week experiment, we investigated the response of microeukaryotic and bacterial communities to different types of OM inputs comprising five ratios of two common phytoplankton species in the Baltic Sea, the diatom Skeletonema marinoi and filamentous cyanobacterium Nodularia spumigena. Metabarcoding analyses on 16S and 18S ribosomal RNA (rRNA) at the experiment termination revealed subtle but significant changes in diversity and community composition of microeukaryotes in response to settling OM quality. Sediment bacteria were less affected, although we observed a clear effect on denitrification gene expression (nirS and nosZ), which was positively correlated with increasing proportions of cyanobacteria. Altogether, these results suggest that future changes in OM input to the seafloor may have important effects on both the composition and function of microbenthic communities.
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| 10. |
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