A longitudinal snapshot of pioneer plant patterns along lowland temperate rivers

Overexploitation of water, loss of dynamism and current climate change cause river drought and baseflow events that are globally increasingly intense and prolonged. This strongly affects riverine plant communities, especially those of seasonally exposed sediments. However, few data are available concerning this key component of river biodiversity currently. Furthermore, the role of alien species is expected to be important in riverbeds since fluvial corridors have an extraordinary susceptibility to be invaded and act as primary routes for invader dispersal. This study provides a systematic investigation of the longitudinal patterns of pioneer plants—in terms of richness and cover—in three mid-size rivers (Ticino, Adda and Oglio rivers) in northern Italy, from 15 different sampling sites. The alien plants dominated the pioneer richness (52 out of 91 species, 57% of the total richness found), whereas plant cover followed less-defined patterns. Along the upstream–downstream gradient, native plants showed a steep decline (−69% in richness and −52% in cover rates on average), only partially offset by the local (extremely variable) changes in alien taxa (−41% on average, in the range of −2.7 to +4.1 species per plot and with cover rates varying form −10 to +1,018%). The magnitude and sign of the detected trends strongly reflected individual river identity. Further investigations are required to better assess the role of hydromorphology in driving the riverine pioneer plant assemblages

The importance of being petioled: leaf traits and resource-use strategies in Nuphar lutea

Intraspecific trait variability (ITV) can be considerably high and reveal plant local adaptation. The aim of this study is to investigate ITV of leaf traits (including petioles) in a rooted floating-leaved macrophyte (Nuphar lutea) at the local scale. We expected to see changes in resource-use strategies in relation to water and sediment properties. 96 leaves were sampled in a hyper-eutrophic shallow lake in central Italy, together with environmental parameters. Results highlight the influence of water depth and sediments in modulating environmental conditions and thus leaf traits. Leaf area and fresh and dry weight increased with water depth, a relation that catches the construction costs of petioles. The negative relation found between specific petiole area and conductivity suggests a stress imposed by high nutrient availability which triggers unfavorable conditions for N. lutea. We demonstrated the relevance of petiole traits for a rooted macrophyte. Petiole aerenchyma or photosynthetic extra surfaces fundamentally contribute to fit the environment, opening new questions for the functional investigation of macrophytes. Excluding petioles in the assessment of leaf traits reduces the possibility to understand the ecological/adaptive processes of nympheids. New data are urgently needed to increase the number of data and species to be analyzed

Pioneer annual vegetation of gravel-bed rivers: First insights on environmental drivers from three Apennine streams

A huge knowledge gap exists on riverine pioneer vegetation. Despite its relevance in regulating the C metabolism at the catchment scale, and the triggering role in shrubs and trees establishment along riverbanks, little data is available on its environmental determinants. Indeed, most existing knowledge in this field refers to woody species or aquatic macrophytes neglecting the ecosystem relevance of ephemeral herbaceous vegetation. Focusing on three gravel bed rivers located in northern Italy (Baganza, Nure and Parma streams), the present study is aimed to evaluate the riverine ephemeral plant richness, considering both native and alien taxa, and the role of hydrogeomorphological disturbance and sediment quality in the observed richness patterns. At higher disturbance rates (e.g., larger river sizes), our data indicates a progressive decrease in overall plant richness, but also an increase in the coverage-abundance rates mainly due to alien species. This evidence confirms that variations in hydrology imply changes in pioneer plant species richness at in-stream periodically exposed sediments. More attention must be given to the vulnerability of pioneer vegetation to climate change and direct human impacts to fully understand the functioning of lotic ecosystems, especially the non-perennial ones

Functional traits in macrophyte studies: Current trends and future research agenda

The use of functional traits (FTs) can provide quantitative information to explain macrophyte ecology more effectively than traditional taxonomic-based methods. This research aims to elucidate the trait-based approaches used in recent macrophyte studies to outline their applications, shortcomings, and future challenges. A systematic literature review focused on macrophytes and FTs was carried out on Scopus database (last accessed May 2020). The latest 520 papers published from 2010 to 2020, which represent 70 % of the whole literature selected since 1969, were carefully screened. Reviewed studies mainly investigated: 1) the role of FTs in shaping communities; 2) the responses of macrophytes to environmental gradients; 3) the application of FTs in monitoring anthropic pressures; and 4) the reasons for success of invasive species. Studied areas were concentrated in Europe (41 %) and Asia (32 %), overlooking other important biodiversity hotspots, and only 6.2 % of the world macrophytes species were investigated in dedicated single species studies. The FTs most commonly used include leaf economic and morphological traits, and we noticed a lack of attention on root traits and in general on spatial traits patterns, as well as a relatively poor understanding of how FTs mediate biotic interactions. High-throughput techniques, such as remote sensing, allow to map fine-scale variability of selected traits within and across systems, helping to clarify multiple links of FTs with ecological drivers and processes. We advise to promote investigations on root traits, and to push forward the integration of multiple approaches to better clarify the role of macrophytes at multiple scales

The incidence of alien species on the taxonomic, phylogenetic, and functional diversity of lentic and lotic communities dominated by Phragmites australis (Cav.) Steud

This study aims to investigate, for the first time, the multiple diversity harbored in plant communities dominated by P. australis, discriminating between lentic and lotic habitats. We focused on the incidence of alien species on taxonomical, phylogenetic and functional diversity. Although it was hypothesized that ecological differences between habitats (lentic vs. lotic) could lead to plant adaptive trade-offs, results showed that the P. australis dominance affected overall plant diversity in the same way in both target habitats. Similarly, the two compared habitats hosted a similar alien species richness and relative abundance. Different results were observed based on whether the alien species richness or their relative abundance were considered regarding the incidence of alien species. Increasing alien species richness in lentic habitats resulted in increased taxonomic, phylogenetic and functional diversity. Instead, in lotic habitats, it promoted a decrease in taxonomic and functional diversity. In contrast, the increase in the relative abundance of alien species resulted in increased taxonomic, phylogenetic and functional diversity in both habitats. Choosing relative abundance vs richness of aliens in lotic stands can have a different impact in evaluating the effect of aliens on various components of diversity

The Origin of Extended Disk Galaxies at z=2

Galaxy formation models typically assume that the size and rotation speed of galaxy disks are largely dictated by the mass, concentration, and spin of their surrounding dark matter haloes. Equally important, however, are the fraction of baryons in the halo that collect into the central galaxy, as well as the net angular momentum that they are able to retain during its assembly process. We explore the latter using a set of four large cosmological N-body/gasdynamical simulations drawn from the OWLS (OverWhelmingly Large Simulations) project. These runs differ only in their implementation of feedback from supernovae. We find that, when expressed as fractions of their virial values, galaxy mass and net angular momentum are tightly correlated. Galaxy mass fractions, m_d=M_gal/M_vir, depend strongly on feedback, but only weakly on halo mass or spin over the halo mass range explored here (M_vir>1e11 h^{-1}M_sun). The angular momentum of a galaxy, j_d=J_gal/J_vir, correlates with m_d in a manner that is insensitive to feedback and that deviates strongly from the simple j_d = m_d assumption often adopted in semi-analytic models of galaxy formation. The m_d-j_d correlation implies that, in a given halo, galaxy disk size is maximal when the central galaxy makes up a substantial fraction (~20%-30%) of all baryons within the virial radius. At z=2, such systems may host gaseous disks with radial scale lengths as large as those reported for star-forming disks by the SINS survey, even in moderately massive haloes of average spin. Extended disks at z=2 may thus signal the presence of systems where galaxy formation has been particularly efficient, rather than the existence of haloes with unusually high spin parameter.Comment: 5 pages, 4 figures. Accepted for publication in MNRAS Letters. Minor changes to match published versio

Anticorrosion Protection by Amine-Ionic Liquid Mixtures: Experiments and Simulations

The mixtures of aqueous amines and ionic liquids (ILs) are considered as potential solvents for CO2 capture. We report corrosion and CO2 absorption behavior of the mixed IL-amine solutions. The absorption tests were performed at 318.15 K under 0.1-2.7 MPa. The corrosion tests were carried out at 318.15 K under 2.7 MPa. Addition of [bmim][BF4] in aqueous alkanolamine solutions reduces corrosion rate for MEA by up to 72%. The CO, absorption capacity in the mixtures falls between those of aqueous MDEA and pure IL. These results allow to choose the working pressure range as a function of other parameters, such as gas pressure and mixture viscosity. According to the simulations, [bmim][BF4] participates in the gas capture through H-bonding, although the number of amine molecules is enough to capture all supplied CO, molecules. The equilibrium of the chemisorption reaction is, therefore, modified upon the stepwise IL addition. An ideal IL content for preventing corrosion is 10% w/w.CNPqHewlett-Packard Brasil LtdaCAPESPontif Catholic Univ Rio Grande Sul PUCRS, Postgrad Program Mat Engn & Technol, Ave Ipiranga 6681, BR-90619900 Porto Alegre, RS, BrazilPontif Catholic Univ Rio Grande Sul PUCRS, Sch Chem, Ave Ipiranga 6681, BR-90619900 Porto Alegre, RS, BrazilPontif Catholic Univ Rio Grande Sul PUCRS, Sch Engn, Ave Ipiranga 6681, BR-90619900 Porto Alegre, RS, BrazilUniv Fed Sao Paulo, BR-04021001 Sao Paulo, SP, BrazilUniv Fed Sao Paulo, BR-04021001 Sao Paulo, SP, BrazilWeb of Scienc

The discovery of the most UV-Lya luminous star-forming galaxy: a young, dust- and metal-poor starburst with QSO-like luminosities

We report the discovery of BOSS-EUVLG1 at z=2.469, by far the most luminous, almost un-obscured star-forming galaxy known at any redshift. First classified as a QSO within the Baryon Oscillation Spectroscopic Survey, follow-up observations with the Gran Telescopio Canarias reveal that its large luminosity, MUV = -24.40 and log(L_Lya/erg s-1) = 44.0, is due to an intense burst of star-formation, and not to an AGN or gravitational lensing. BOSS-EUVLG1 is a compact (reff = 1.2 kpc), young (4-5 Myr) starburst with a stellar mass log(M*/Msun) = 10.0 +/- 0.1 and a prodigious star formation rate of ~1000 Msun yr-1. However, it is metal- and dust-poor (12+log(O/H) = 8.13 +/- 0.19, E(B-V) = 0.07, log(LIR/LUV) < -1.2), indicating that we are witnessing the very early phase of an intense starburst that has had no time to enrich the ISM. BOSS-EUVLG1 might represent a short-lived (<100 Myrs), yet important phase of star-forming galaxies at high redshift that has been missed in previous surveys. Within a galaxy evolutionary scheme, BOSS-EUVLG1 could likely represent the very initial phases in the evolution of massive quiescent galaxies, even before the dusty star-forming phase.Comment: 6 pages, 3 figures, 1 table. Accepted for publication in MNRAS Letter

The First Billion Years project: constraining the dust attenuation law of star-forming galaxies at z ≃ 5

We present the results of a study investigating the dust attenuation law at $z\simeq 5$, based on synthetic spectral energy distributions (SEDs) calculated for a sample of N=498 galaxies drawn from the First Billion Years (FiBY) simulation project. The simulated galaxies at $z\simeq 5$, which have M$_{1500} \leq -18.0$ and $7.5 \leq \rm{log(M/M}_{\odot}\rm{)} \leq 10.2$, display a mass-dependent $\alpha$-enhancement, with a median value of $[\alpha/\rm{Fe}]_{z=5}~\simeq~4~\times~[\alpha/\rm{Fe}]_{Z_{\odot}}$. The median Fe/H ratio of the simulated galaxies is $0.14\pm0.05$ which, even including the effects of nebular continuum, produces steep intrinsic UV continuum slopes; $\langle \beta_{i} \rangle = -2.4 \pm 0.05$. Using a set of simple dust attenuation models, in which the wavelength-dependent attenuation is assumed to be of the form $A(\lambda) \propto \lambda^{n}$, we explore the parameter values which best reproduce the observed $z=5$ luminosity function (LF) and colour-magnitude relation (CMR). We find that a simple model in which the absolute UV attenuation is a linearly increasing function of log stellar mass, and the dust attenuation slope ($n$) is within the range $-0.7 \leq n \leq-0.3$, can successfully reproduce the LF and CMR over a wide range of stellar population synthesis model (SPS) assumptions. This range of attenuation curves is consistent with a power-law fit to the Calzetti attenuation law in the UV ($n=-0.55$), and other similarly `grey' star-forming galaxy attenuation curves recently derived at $z\simeq2$. In contrast, attenuation curves as steep as the Small Magellanic Cloud (SMC) extinction curve ($n=-1.24$) are formally ruled out. Finally, we show that our models are consistent with recent 1.3mm ALMA observations of the Hubble Ultra Deep Field (HUDF), and predict the form of the $z\simeq5$ IRX$-\beta$ relation.Comment: 23 pages, 19 figures, accepted for publication in MNRA

Dark matter halo concentrations in the Wilkinson Microwave Anisotropy Probe year 5 cosmology

We use a combination of three large N-body simulations to investigate the dependence of dark matter halo concentrations on halo mass and redshift in the WMAP year 5 cosmology. The median relation between concentration and mass is adequately described by a power-law for halo masses in the range 10^11 - 10^15 Msol/h and redshifts z < 2, regardless of whether the halo density profiles are fit using NFW or Einasto profiles. Compared with recent analyses of the Millennium Simulation, which uses a value of sigma_8 that is higher than allowed by WMAP5, z = 0 halo concentrations are reduced by factors ranging from 23 per cent at 10^11 Msol/h to 16 per cent at 10^14 Msol/h. The predicted concentrations are much lower than inferred from X-ray observations of groups and clusters.Comment: 6 pages, 4 figures, Accepted by MNRAS letters. Version 4: Typo fixe