Age Gradient Research Articles

Changes in Bulk and Rhizosphere Soil Microbial Diversity and Composition Along an Age Gradient of Chinese Fir (Cunninghamia lanceolate) Plantations in Subtropical China.

Soil microorganisms play key roles in biogeochemical cycling in forest ecosystems. However, whether the responses of microbial community with stand development differed in rhizosphere and bulk soils remains unknown. We collected rhizosphere and bulk soil in Chinese fir plantations with different stand ages (7a, 15a, 24a, and 34a) in subtropical China, and determined bacterial and fungal community variation via high-throughput sequencing. The results showed that soil bacterial, but not fungal, community diversity significantly differed among stand ages and between rhizosphere and bulk soils (p < 0.05). The differences in Shannon–Wiener and Simpson’s indices between rhizosphere and bulk soil varied with stand age, with significant higher soil bacterial diversity in rhizosphere than bulk soils in 7a and 34a plantations (p < 0.05), but there were no significant difference in soil bacterial diversity between rhizosphere and bulk soils in 15a and 24a plantations (p > 0.05). Soil microbial community composition varied significantly with stand age but not between the rhizosphere and bulk soil. The dominant bacterial phyla at all ages were Acidobacteria and Proteobacteria, while the dominant fungal phyla were Ascomycota and Basidiomycota in both rhizosphere and bulk soil. They showed inconsistent distribution patterns along stand age gradient (7–34a) in the rhizosphere and bulk soil, suggesting distinct ecological strategy (r-strategist vs. k-strategist) of different microbial taxa, as well as changes in the microenvironment (i.e., nutrient stoichiometry and root exudates). Moreover, bacterial and fungal community composition in rhizosphere and bulk soil were governed by distinct driving factors. TP and NH4+–N are the two most important factors regulating bacterial and fungal community structure in rhizosphere soil, while pH and NO3––N, DON, and TN were driving factors for bacterial and fungal community structure in bulk soil, respectively. Collectively, our results demonstrated that the changes in microbial diversity and composition were more obvious along stand age gradients than between sampling locations (rhizosphere vs. bulk soil) in Chinese fir plantations.

Evidence in favour of density wave theory through age gradients observed in star formation history maps and spatially resolved stellar clusters

ABSTRACT Quasi-stationary density wave theory predicts the existence of an age gradient across the spiral arms with a phase crossing at the corotation radius. We have examined evidence for such age gradients using star formation history (SFH) maps derived from lightning, a spectral energy distribution fitting procedure, and by using spatially resolved stellar clusters. Three galaxies from the LEGUS survey were used to analyse the azimuthal offsets of spatially resolved stellar clusters. Kernel density estimation plots of azimuthal cluster distance offsets reveal prominent central peaks and secondary peaks on the positive side, relative to the density wave for NGC 5194 and NGC 5236. These secondary downstream peaks in the cluster distributions show overall evidence for an age gradient. NGC 628 shows secondary peaks on both sides of the density wave. The cluster distributions also show an increasing spatial spread with age, consistent with the expectation that they were born in the density wave. SFH maps of 12 nearby galaxies were analysed using spirality, a matlab-based code, which plots synthetic spiral arms over FITS images. The SFH maps reveal a gradual decrement (tightening) in pitch angles with increasing age. By analysing the pitch angle differences between adjacent age bins using the error function, the average of the probabilities shows a $69{{\ \rm per\ cent}}\pm 25{{\ \rm per\ cent}}$ chance that the pitch angle values decrease (tighten) with increasing age. Thus, we see a tightening of the spiral pattern in galaxies, both when segregating stellar populations specifically by age or more generally by colour, as was shown in our previous studies.

The VISCACHA survey – IV. The SMC West Halo in 8D

ABSTRACT The structure of the Small Magellanic Cloud (SMC) is very complex, in particular in the periphery that suffers more from the interactions with the Large Magellanic Cloud (LMC). A wealth of observational evidence has been accumulated revealing tidal tails and bridges made up of gas, stars, and star clusters. Nevertheless, a full picture of the SMC outskirts is only recently starting to emerge with a 6D phase-space map plus age and metallicity using star clusters as tracers. In this work, we continue our analysis of another outer region of the SMC, the so-called West Halo, and combined it with the previously analysed Northern Bridge. We use both structures to define the Bridge and Counter-bridge trailing and leading tidal tails. These two structures are moving away from each other, roughly in the SMC–LMC direction. The West Halo form a ring around the SMC inner regions that goes up to the background of the Northern Bridge shaping an extended layer of the Counter-bridge. Four old Bridge clusters were identified at distances larger than 8 kpc from the SMC centre moving towards the LMC, which is consistent with the SMC–LMC closest distance of 7.5 kpc when the Magellanic Bridge was formed about 150Myr ago; this shows that the Magellanic Bridge was not formed only by pulled gas, but it also removed older stars from the SMC during its formation. We also found age and metallicity radial gradients using projected distances on sky, which are vanished when we use the real 3D distances.

Quenching time-scales in the IllustrisTNG simulation

ABSTRACT The time-scales for galaxy quenching offer clues to its underlying physical drivers. We investigate central galaxy quenching time-scales in the IllustrisTNG 100-1 simulation, their evolution over time, and the pre-quenching properties of galaxies that predict their quenching time-scales. Defining quenching duration τq as the time between crossing specific star formation rate (sSFR) thresholds, we find that ${\sim} 40{{\ \rm per\ cent}}$ of galaxies quench rapidly with τq &amp;lt; 1 Gyr, but a substantial tail of galaxies can take up to 10 Gyr to quench. Furthermore, 29 per cent of galaxies that left the star-forming main sequence (SFMS) more than 2 Gyr ago never fully quench by z = 0. While the median τq is fairly constant with epoch, the rate of galaxies leaving the SFMS increases steadily over cosmic time, with the rate of slow quenchers being dominant around z ∼ 2–0.7. Compared to fast quenchers (τq &amp;lt; 1 Gyr), slow-quenching galaxies (τq &amp;gt; 1 Gyr) were more massive, had more massive black holes, had larger stellar radii, and accreted gas with higher specific angular momentum (AM) prior to quenching. These properties evolve little by z = 0, except for the accreting gas AM for fast quenchers, which reaches the same high AM as the gas in slow quenchers. By z = 0, slow quenchers also have residual star formation in extended gas rings. Using the expected relationship between stellar age gradient and τq for inside-out quenching we find agreement with Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) integral field unit (IFU) observations. Our results suggest the accreting gas AM and potential well depth determine the quenching time-scale.

Outcomes of Surgical Bioprosthetic Aortic Valve Replacement in Patients Aged ≤65 and >65 Years

BackgroundImplantation of a bioprosthetic valve is a reasonable choice for patients aged > 65 years. For middle-aged patients there is less certainty about whether a mechanical or bioprosthetic valve is best. MethodsThe Pericardial Surgical Aortic Valve Replacement (PERIGON) Pivotal Trial is evaluating the safety and efficacy of the Avalus bioprosthesis (Medtronic). We evaluated clinical and echocardiographic outcomes through 5 years of follow-up, stratified by age ≤ 65 and >65 years. ResultsTwo hundred seventy-one patients (24.2%) were ≤65 years old and 847 (75.8%) >65 years old. Most patients in both groups were men (217 [80.1%] vs 623 [73.6%], respectively; P = .031). Younger patients had a lower Society of Thoracic Surgeons risk of mortality (1.1% ± 0.9% vs 2.2% ± 1.4%, P < .001), better baseline New York Heart Association class (P = .004), and fewer comorbidities than older patients. At 5 years mortality was lower among younger than older patients (5.3% vs 14.0%, P < .001) and no cases of structural valve deterioration occurred in either group. Effective orifice area was similar between age groups (P = .11), and mean gradient was 13.9 ± 5.4 vs 12.0 ± 4.1 mm Hg (P < .001). Multivariable linear regression identified several parameters associated with mean aortic gradient at 5 years, including baseline age and mean aortic gradient, discharge stroke volume index and EOA, and implanted valve size. Ninety-five percent of patients were in New York Heart Association class I/II through 5 years in both age groups (P = .85). ConclusionsFindings from this analysis demonstrate satisfactory safety, hemodynamic performance, and durability of the Avalus bioprosthesis through a 5-year follow-up in patients aged ≤ 65 and >65 years.

The age gradients of galaxies in EAGLE: outside-in quenching as the origin of young bulges in cluster galaxies

ABSTRACT Many disc galaxies in clusters have been found with bulges of similar age or younger than their surrounding discs, at odds with field galaxies of similar morphology and their expected inside-out formation. We use the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations to test potential origins for this difference in field and cluster galaxies. We find, in agreement with observations, that on average disc-dominated field galaxies in the simulations have older inner regions, while similar galaxies in groups and clusters have similarly aged or younger inner regions. This environmental difference is a result of outside-in quenching of the cluster galaxies. Prior to group/cluster infall, galaxies of a given present-day mass and morphology exhibit a similar evolution in their specific star formation rate (sSFR) profiles. Post-infall, the outer sSFRs of group and cluster galaxies significantly decrease due to interstellar medium stripping, while the central sSFR remains similar to field galaxies. Field disc galaxies instead generally retain radially increasing sSFR profiles. Thus, field galaxies continue to develop negative age gradients (younger discs), while cluster galaxies instead develop positive age gradients (younger bulges).

Response of the Christchurch groundwater system to exploitation: Carbon-14 and tritium study revisited

The Christchurch groundwater system is an exceptional water resource with very high drinking water quality supplying all the water requirements of the city. The groundwater system has changed over the years because of rising groundwater abstraction due to increasing population and development. The present (2017) data revealed slightly older 14C ages and increasingly steep west-east age gradients compared to the earlier work from 1976 to 2006, showing continued upflow of deep water into the exploited aquifers which is much older on the east (coastal) side than on the west (inland) side. In addition, the 3H ages for wells on the west side of the system are often much younger than their 14C ages showing that there is input of young shallow water to the wells in addition to the deep water input. Application of a binary model identifies the ages and amounts of the two components, showing that the young component is becoming younger although smaller as a proportion of the flow, and the old component from depth is becoming larger. Newly completed wells near the Waimakariri River have allowed identification of the young component, which is almost entirely composed of very young Waimakariri River seepage at all depths and therefore has very little chemical loading. Instead any chemical input (e.g. chloride, nitrate) to the Christchurch aquifers is being brought in by the old deep component which on the western side of the Christchurch system is derived from rainfall recharge on the developing Ashley-Waimakariri Plains area (plus river seepage). Chemical traces of this deep input from the northwest are at present very subtle, although more appreciable signals are seen in some wells further to the north of Christchurch. In the future, slowly increasing chemical input to the Christchurch aquifers on the west side of the system is to be expected as abstraction increases.

Severe Rheumatic Mitral Stenosis, Worse Left Atrial Mechanics is Closely Associated with Echo Criteria for Intervention.

Background:Rheumatic mitral valve (MV) stenosis is associated with progressive left atrial (LA) fibrosis and functional impairment, Pulmonary artery systolic pressure (PASP) and right ventricular (RV) dysfunction. The aims of the study were to determine in those patients with severe MV stenosis if LA mechanical function as assessed by speckle tracking echocardiography could identify those with increased PASP, atrial fibrillation (AFib), and RV dysfunction.Subjects and Methods:Patients with severe MV stenosis were identified from the institutional echo database. Echocardiograms were read off line and measurements included atrial and ventricular strain. Patients were divided into tertiles of LA reservoir strain (LASr) values and data compared between the groups.Results:Ninety-seven patients, 67 females, mean age 47.4 ± 11.9 years, had MV mean gradient of 8.3 ± 5.1 mmHg, MV area by pressure half time of 1.3 ± 0.3 cm2 and LASr of 11.18% ± 6.4%. Those patients in the lowest LASr tertile had more AFib (72%, P = 0.0001), PASP >50 mm Hg (39%, P = 0.005), and worst RV impairment. In multivariable logistic regression analysis, LASr, age, and mean MV gradient were the independent predictors of AFib and PASP >50 mm Hg. Cutoffs, determined by receiver operating characteristic curve analysis had high specificity for the composite outcome of Afib and PASP >50 mmHg (85% for LASr <7.7%).Conclusion:In severe MV stenosis LASr, age and mean MV gradient, are independent predictors of Afib and PASP >50 mmHg. LASr <7.7% has high sensitivity and specificity in identifying those who meet ESC guideline 2017 criteria for valve intervention, suggesting its potentially helpful addendum to the surveillance of patients with MV stenosis.

Woody Species Diversity and Carbon Stock of Church Forests Along Age Gradient in Dangila District, Awi-Zone, Ethiopia

Woody Species Diversity and Carbon Stock of Church Forests Along Age Gradient in Dangila District, Awi-Zone, Ethiopia

Spatially Resolved Stellar Spectroscopy of the Ultra-diffuse Galaxy Dragonfly 44. III. Evidence for an Unexpected Star Formation History under Conventional Galaxy Evolution Processes

Abstract We use the Keck Cosmic Web Imager integral field unit spectrograph to (1) measure the global stellar population parameters for the ultra-diffuse galaxy (UDG) Dragonfly 44 (DF44) to much higher precision than previously possible for any UDG and (2) for the first time measure spatially resolved stellar population parameters of a UDG. We find that DF44 falls below the mass–metallicity relation established by canonical dwarf galaxies both in and beyond the Local Group. We measure a flat radial age gradient ( m logage = + 0.01 − 0.08 + 0.08 log Gyr kpc−1) and a flat to positive metallicity gradient ( m [ Fe / H ] = + 0.09 − 0.12 + 0.11 dex kpc−1), which are inconsistent with the gradients measured in similarly pressure-supported dwarf galaxies. We also measure a negative [Mg/Fe] gradient ( m [ Mg / Fe ] = − 0.20 − 0.18 + 0.18 ) dex kpc−1 such that the central 1.5 kpc of DF44 has stellar population parameters comparable to metal-poor globular clusters. Overall, DF44 does not have internal properties similar to other dwarf galaxies and is inconsistent with it having been puffed up through a prolonged, bursty star formation history, as suggested by some simulations. Rather, the evidence indicates that DF44 experienced an intense epoch of “inside-out” star formation and then quenched early and catastrophically, such that star formation was cut off more quickly than in canonical dwarf galaxies.

Stellar populations with MEGARA: The inner regions of NGC 7025

Context. This paper aims to determine the capabilities of the MEGARA spectrograph at the Gran Telescopio Canarias (GTC), which is an optical integral-field unit, for studying stellar populations. We also aim to exploit its combination of high spectral (R ∼ 6000, 12 000 and 20 000) and spatial (0.62″) resolution within its 12″​​.5 × 11″​​.3 field of view. We do this by analysing the commissioning data of the nearby S0a galaxy NGC 7025. Aims. We establish a systematic method through which we can determine the properties of the stellar populations in the observations made with MEGARA, more specifically, within the MEGADES legacy project. For this paper in particular, we determine the properties of the stellar populations of NGC 7025. Methods. We used MEGARA observations of galaxy NGC 7025 that were taken during the commissioning phase of the instrument. We applied different approaches to estimate the properties of the stellar populations with the highest possible certainty. In addition to the specific study of NGC 7025 and in the context of the MEGADES survey, we have carried out a number of tests to determine the expected errors (including potential biases) in these star formation history (SFH) derivations as a function of these parameters, namely spectral setup, signal-to-noise ratio, σ, and the SFH itself. Results. All the studies we conduct (both full spectral fitting and absorption line indices) of the stellar populations of NGC 7025 indicate that the stars that form its bulge have supersolar metallicity and considerably old ages (∼10 Gyr) in general. Using three different combinations of MEGARA spectral setups, we determined that the bulge of NGC 7025 has smild negative mass-weighted age gradient. For the more detailed SFH, our results indicate that in addition to a rather constant star formation at early epochs, a peak in the formation history of the stars in the bulge is also found 3.5–4.5 Gyr ago. This partly explains the mass-weighted age gradients we measured. Conclusions. The scenario presented in NGC 7025 is that of an isolated galaxy under secular evolution that about 3.5–4.5 Gyr ago likely experienced a minor merger (mass ratio 1/10) that induced an increase in star formation and also perturbed the morphology of its outer disc. In addition to these specific results for NGC 7025, we report different lessons learned for the ongoing exploitation of the MEGADES survey with the GTC, such as the need to obtain combined observations in the LR-B + LR-V setups and a signal-to-noise ratio of at least 20 per Å.

Why Does the Severity of COVID-19 Differ With Age?: Understanding the Mechanisms Underlying the Age Gradient in Outcome Following SARS-CoV-2 Infection.

Although there are many hypotheses for the age-related difference in the severity of COVID-19, differences in innate, adaptive and heterologous immunity, together with differences in endothelial and clotting function, are the most likely mechanisms underlying the marked age gradient. Children have a faster and stronger innate immune response to SARS-CoV-2, especially in the nasal mucosa, which rapidly controls the virus. In contrast, adults can have an overactive, dysregulated and less effective innate response that leads to uncontrolled pro-inflammatory cytokine production and tissue injury. More recent exposure to other viruses and routine vaccines in children might be associated with protective cross-reactive antibodies and T cells against SARS-CoV-2.There is less evidence to support other mechanisms that have been proposed to explain the age-related difference in outcome following SARS-CoV-2 infection, including pre-existing immunity from exposure to common circulating coronaviruses, differences in the distribution and expression of the entry receptors ACE2 and TMPRSS2, and difference in viral load.

SDSS-IV MaNGA: integral-field kinematics and stellar population of a sample of galaxies with counter-rotating stellar discs selected from about 4000 galaxies

ABSTRACT We present the integral-field kinematics and stellar population properties of 64 galaxies (61 are Early-Type galaxies; ETGs) with Counter-Rotating stellar Disks (CRD) selected from about 4000 galaxies in the MaNGA survey, based on evidence of counter-rotation or two velocity dispersion peaks in the kinematic maps. For 17 CRDs, the counter-rotating components can also be separated spectroscopically. The frequency of CRDs in MaNGA is &amp;lt;5 per cent for ellipticals, &amp;lt;3 per cent for lenticulars, and &amp;lt;1 per cent for spirals (at 95 per cent confidence level), consistent with previous estimates. We produced age and metallicity maps, and compared the stellar population properties to those of the general ETGs population. We found that CRDs have similar trends in age and metallicity to ETGs, but are less metallic at low masses, and show flatter age and steeper metallicity gradients, on average. A comparison of the velocity fields of the ionized gas and the stars reveals that in 33 cases the gas corotates with either the inner (15 cases) or outer (18 cases) stellar disc, and in nine cases it is misaligned. In most cases the gas corotates with the younger disc. Evidence of multimodality in the stellar population is found in 31 galaxies, while the 14 youngest and least massive galaxies show ongoing star formation; 14 galaxies, instead, exhibit unimodality, and are the oldest and most massive. As a general result, our work indicates that CRDs form primarily via gas accretion in retrograde rotation with respect to a pre-existing stellar disc.

Formation of galactic bulges from the cold gas filaments in high-redshift dark matter haloes

ABSTRACT Formation process(es) of galactic bulges are not yet clarified, although several mechanisms have been proposed. In a previous study, we suggested one possibility that galactic bulges have been formed from the cold gas inflowing through surrounding hot halo gas in massive dark matter haloes at high redshifts. It was shown that this scenario leads to the bulge-to-total stellar mass ratio increasing with the galaxy mass, in agreement with the well-known observed trend. We here indicate that it also reproduces recent observational results that the mean stellar age of the bulge increases with the galaxy mass while the age gradient across the bulge decreases. We infer that this formation path applies mainly to high-mass galaxies and the bulges in lower mass galaxies have different origins such as secular formation from the disc material.

Soil Fertility Changes With Climate and Island Age in Galápagos: New Baseline Data for Sustainable Agricultural Management

While the extended absence of human influence has led to matchless natural conditions on the Galápagos archipelago, agricultural activities on the inhabited islands are increasingly affecting soil health and functioning. However, a systematic assessment of the agricultural soils on the Galápagos Islands is still absent. Plate tectonics and hotspot volcanism cause an eastward drift of the archipelago and result in a west-to-east soil age gradient from approx. 1 to 1,000 ka. In addition, precipitation regimes change from arid to humid with elevation on the higher-standing islands. The objective of this study was to investigate differences in soil fertility parameters and Mehlich (III)-extractable nutrient levels along these gradients in order to provide baseline information for sustainable agricultural management. Topsoil samples (0–20 cm) from 125 farms of the islands Isabela, Santa Cruz and San Cristóbal were analyzed. Gravel and sand content, pH, electrical conductivity, cation exchange capacity, base saturation, soil organic C and total N content tended to decrease with increasing island age, while clay content, soil macroaggregate stability, plant-available water and bulk density increased. Mehlich (III)-extractable base cations Ca, K, Mg and Na as well as P, Fe and Zn showed a decreasing tendency from the youngest to the oldest island, while Mn increased with island age. Mehlich (III)-extractable Cu and Na reached their highest levels on the most intensively farmed, intermediate-aged island Santa Cruz, likely related to anthropogenic inputs and irrigation with brackish water, respectively. Changes along the altitudinal climate gradient within the studied islands were most significant for soil pH, base saturation, and Mehlich (III)-extractable Ca and Mn. Our results highlight the importance of site-specific agricultural management to account for the strong heterogeneity in soil parameters among and within the Galápagos archipelago. The data provided herein shall serve as a baseline for targeted future management strategies to avoid soil degradation, restore and maintain soil functioning and, hence, sustain the soils’ provision of ecosystem services in this unique archipelago.

Soil Microbial Resource Limitations and Community Assembly Along a Camellia oleifera Plantation Chronosequence.

Understanding soil microbial element limitation and its relation with the microbial community can help in elucidating the soil fertility status and improving nutrient management of planted forest ecosystems. The stand age of a planted forest determines the aboveground forest biomass and structure and underground microbial function and diversity. In this study, we investigated 30 plantations of Camellia oleifera distributed across the subtropical region of China that we classified into four stand ages (planted <9 years, 9–20 years, 21–60 years, and >60 years age). Enzymatic stoichiometry analysis showed that microbial metabolism in the forests was mainly limited by C and P. P limitation significantly decreased and C limitation slightly increased along the stand age gradient. The alpha diversity of the soil microbiota remained steady along stand age, while microbial communities gradually converged from scattered to clustered, which was accompanied by a decrease in network complexity. The soil bacterial community assembly shifted from stochastic to deterministic processes, which probably contributed to a decrease in soil pH along stand age. Our findings emphasize that the stand age regulated the soil microbial metabolism limitation and community assembly, which provides new insight into the improvement of C and P management in subtropical planted forest.

Spatially Resolving the Star Formation Histories of Three Nearby Nuclear Star Clusters

Abstract The formation of nuclear star clusters (NSCs) remains an open question. In this work, we use spatially-resolved HST/STIS spectroscopic observations of three nearby NSCs (hosted by NGC 5102, NGC 5206, and NGC 205) to constrain their formation histories by exploring radial variations of the stellar populations within each cluster. Utilizing full-spectrum fitting, we find substantial age and metallicity gradients within the central 0.″9 (16 pc) of the NSC in NGC 5102 where populations near the center are young/metal-rich (age ∼400 Myr and [M/H] ∼ −0.4) and become older/metal-poor at larger radii (mean age ∼1 Gyr and mean [M/H] ∼ −1.6 in the radial range [0.″3, 0.″9]). This behavior suggests that the young/metal-rich population at the center was formed from a period of in situ formation, while the older/metal-poor populations were likely formed by inspiraled globular clusters. The two broad populations observed in the NGC 5102 NSC (young/metal-rich and old/metal-poor) appear to be linked to the transition between the two morphological components of the NSC derived from the surface-brightness profile in Nguyen et al. (2018). The radial ranges explored in NGC 5206 and NGC 205 were much smaller due to poor data quality; in NGC 5206 we find a similar metallicity gradient to NGC 5102 (but with much lower significance), while the data for NGC 205 is too poor to reach any conclusions. Overall, this data highlights the links between the morphological and stellar population complexity of NSCs and their formation mechanisms.

Investigation of the soil nematode community composition in a monoculture Robusta coffee plantation in Dak Lak, Vietnam

Nematode damage to coffee poses a serious threat to coffee production all over the world, including Vietnam. Accordingly, the nematode community composition could be a reliable indicator of ecological shifts that affect coffee plants' health. Here, we analysed the nematode communities in the rhizosphere of a monoculture Robusta coffee plantation in Dak Lak of the Central Highlands, Vietnam. We found changes in the community composition of nematodes in an age gradient of replanting coffee plants and revealed distinct patterns of nematode distribution in the soils of healthy and diseased plant groups. Further analyses indicate the impact of intensive farming and inefficient nematode controls, which caused disturbances and a gradual decrease of the nematode fauna diversity in the plantation soil. These results can add to a complete prediction model for plant fitness using nematode community composition. • Rhizosphere nematode communities in a monoculture Robusta coffee plantation in Dak Lak, Vietnam, have been assessed. • Pratylenchus are the primary plant-parasitic nematodes in this area. • Remarkably, a high abundance of Chitwoodius and correlation of Aphelenchoides with plant fitness was found. • We show that colonization of coffee plants by plant-parasitic nematodes increases with plant age, and the predominance of these nematodes coincides with a lower diversity of the nematode fauna. • The nematode communities, including several important functional groups, can be utilized as a bio-indicator of plant fitness.

MASCOT: an ESO–ARO legacy survey of molecular gas in nearby SDSS-MaNGA galaxies – I. First data release, and global and resolved relations between H2 and stellar content

ABSTRACT We present the first data release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA)–Arizona Radio Observatory (ARO) Survey of CO Targets (MASCOT), a European Southern Observatory public spectroscopic survey conducted at the ARO. We measure the CO(1–0) line emission in a sample of 187 nearby galaxies selected from the MaNGA survey that has obtained integral field unit (IFU) spectroscopy for a sample of ∼10 000 galaxies at low redshift. The main goal of MASCOT is to probe the molecular gas content of star-forming galaxies with stellar masses &amp;gt;109.5 M⊙ and with associated MaNGA IFU observations and well-constrained quantities like stellar masses, star formation rates, and metallicities. In this paper, we present the first results of the MASCOT survey, providing integrated CO(1–0) measurements that cover several effective radii of the galaxy and present CO luminosities, CO kinematics, and estimated H2 gas masses. We observe that the decline of the galaxy star formation rate with respect to the star formation main sequence increases with the decrease of molecular gas and with a reduced star formation efficiency, in agreement with results of other integrated studies. Relating the molecular gas mass fractions with the slope of the stellar age gradients inferred from the MaNGA observations, we find that galaxies with lower molecular gas mass fractions tend to show older stellar populations close to the galactic centre, while the opposite is true for galaxies with higher molecular gas mass fractions, providing tentative evidence for inside-out quenching.

Testing Models of Triggered Star Formation with Young Stellar Objects in Cepheus OB4

Abstract OB associations are home to newly formed massive stars, whose turbulent winds and ionizing flux create H ii regions rich with star formation. Studying the distribution and abundance of young stellar objects (YSOs) in these ionized bubbles can provide essential insight into the physical processes that shape their formation, allowing us to test competing models of star formation. In this work, we examined one such OB association, Cepheus OB4 (Cep OB4)—a well-suited region for studying YSOs due to its Galactic location, proximity, and geometry. We created a photometric catalog from Spitzer/Infrared Array Camera (IRAC) mosaics in bands 1 (3.6 μm) and 2 (4.5 μm). We supplemented the catalog with photometry from the Wide-field Infrared Survey Explorer, the Two Micron All Sky Survey, IRAC bands 3 (5.8 μm) and 4 (8.0 μm), MIPS 24 μm, and MMIRS near-infrared data. We used color–color selections to identify 821 YSOs, which we classified using the IR slope of the YSOs’ spectral energy distributions, finding 67 Class I, 103 flat spectrum, 569 Class II, and 82 Class III YSOs. We conducted a clustering analysis of the Cep OB4 YSOs and fit their spectral energy distributions. We found many young Class I objects distributed in the surrounding shell and pillars as well as a relative age gradient of unclustered sourcesin the bubble surrounding the OB association, with YSOs generally decreasing in age with distance from the central cluster. Both of these results indicate that the expansion of the H ii region may have triggered star formation in CepOB4.