Deciphering the stability of grassland productivity in response to rainfall manipulation experiments

Aim Rainfall manipulation experiments are essential tools for deciphering the mechanisms leading to variation in ecosystem stability across sites. Here, we gathered articles reporting results of experimental droughts on the above‐ground biomass of grasslands to identify which indices have been used to assess stability, to evaluate the overall grassland responses to drought and to quantify the relative importance of drought characteristics and climatic conditions for explaining variation in stability. Location Global. Time period 1989–2018. Major taxa studied Grasslands. Methods We used meta‐analytical approaches to evaluate overall grassland stability in terms of resistance, recovery and resilience, and multi‐model inference to assess the relative importance of different moderators on explaining the variability of those three stability properties. Results Numerous indices of stability have been used, but they are inadequate for comparisons across sites. After applying standardized indices, we found that grasslands were resilient (biomass remained unchanged 1 year after drought) and exhibited a trade‐off between low resistance (biomass was lost during drought) and high recovery (new biomass was produced after drought). Overall, climatic conditions and drought characteristics (intensity, duration and frequency) were not important to explain the differences in stability observed across grasslands. Main conclusions Grasslands are resilient, but if drought events last > 1 year, there might be long‐term declines of biomass production owing to incomplete recovery. Despite the hundreds of experiments conducted in grasslands across the globe, the results are still inconclusive because of four important shortcomings: 50% of the studies have failed to create drought; 81% have not included recovery and resilience, assessing only resistance; 87% have not applied quantitative indices to assess stability; and < 1% of the studies were conducted on tropical grasslands. We discuss how to overcome those limitations to improve our ability to ensure stable grassland productivity under climate change

Variação temporal de características morfológicas de folhas em dez espécies do Parque Nacional da Restinga de Jurubatiba, Macaé, RJ, Brasil Temporal variation of morphological leaf traits in ten species from Restinga of Jurubatiba National Park, Macaé, Rio de Janeiro State, Brazil

Ordenar espécies em relação a um contínuo de variação de características foliares pode ser útil para inferir sobre a suscetibilidade de uma comunidade a alterações na disponibilidade de recursos e/ou condições ambientais ao longo do tempo. Dez espécies lenhosas de restinga foram acompanhadas quanto à variação temporal de atributos morfológicos foliares. Folhas de dez espécies de restinga foram coletadas nos meses de fevereiro, abril e agosto ao longo de três anos para caracterização da variação temporal da massa de folha por unidade de área (MFA), suculência (SUC), espessura (ESP) e densidade (DEN). As espécies apresentaram uma tendência de valores mais elevados para as características estudadas nos meses mais secos. A partir da comparação sazonal e interanual da MFA, SUC, ESP e DEN sugerimos que a natureza das respostas das plantas à heterogeneidade temporal na disponibilidade de água foi convergente, independentemente do padrão fenológico de produção foliar e filogenia. Portanto, a similaridade observada entre as espécies na dinâmica temporal dos atributos foliares indica a disponibilidade hídrica como um fator determinante para o sucesso na ocupação das planícies arenosas costeiras do norte fluminense.<br>Ranking species in relation to a continuum of leaf-trait variation can be useful to infer community susceptibility to changes in resource availability and/or environmental conditions over time. Leaves of ten woody restinga species were sampled in February, April and August over a period of 3 years to characterize temporal variability of leaf mass per area (LMA), succulence (SUC), thickness (THI) and density (DEN). The species showed a trend toward higher leaf-trait values in dry months during the three-year study. Based on seasonal and interannual comparison of LMA, SUC, THI and DEN we suggest that plant responses to temporal heterogeneity in water availability were convergent, independent of leaf phenological patterns and phylogeny. Thus, the similarity observed among species in temporal dynamics of leaf traits points to water availability as a limiting factor for the success of sandy-coastal-plain occupation in northeastern Rio de Janeiro

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved

Charged-particle multiplicity distributions over a wide pseudorapidity range in proton-proton collisions at √s = 0.9, 7 and 8 TeV

We present the charged-particle multiplicity distributions over a wide pseudorapidity range (−3.4<η<5.0) for pp collisions at s√= 0.9, 7, and 8 TeV at the LHC. Results are based on information from the Silicon Pixel Detector and the Forward Multiplicity Detector of ALICE, extending the pseudorapidity coverage of the earlier publications and the high-multiplicity reach. The measurements are compared to results from the CMS experiment and to PYTHIA, PHOJET and EPOS LHC event generators, as well as IP-Glasma calculations

Charged-particle multiplicity distributions over a wide pseudorapidity range in proton-proton collisions at √s = 0.9, 7, and 8 TeV

We present the charged-particle multiplicity distributions over a wide pseudorapidity range (−3.4<η<5.0) for pp collisions at s√=0.9,7, and 8 TeV at the LHC. Results are based on information from the Silicon Pixel Detector and the Forward Multiplicity Detector of ALICE, extending the pseudorapidity coverage of the earlier publications and the high-multiplicity reach. The measurements are compared to results from the CMS experiment and to PYTHIA, PHOJET and EPOS LHC event generators, as well as IP-Glasma calculations

Elliptic flow of electrons from heavy-flavour hadron decays at mid-rapidity in Pb–Pb collisions at √sNN = 2.76 TeV

The elliptic flow of electrons from heavy-flavour hadron decays at mid-rapidity (|y| < 0.7) is measured in Pb-Pb collisions at sNN−−−√=2.76 TeV with ALICE at the LHC. The particle azimuthal distribution with respect to the reaction plane can be parametrized with a Fourier expansion, where the second coefficient (v2) represents the elliptic flow. The v2 coefficient of inclusive electrons is measured in three centrality classes (0-10%, 10-20% and 20-40%) with the event plane and the scalar product methods in the transverse momentum (pT) intervals 0.5-13 GeV/c and 0.5-8 GeV/c, respectively. After subtracting the background, mainly from photon conversions and Dalitz decays of neutral mesons, a positive v2 of electrons from heavy-flavour hadron decays is observed in all centrality classes, with a maximum significance of 5.9σ in the interval 2< pT < 2.5 GeV/c in semi-central collisions (20-40%). The value of v2 decreases towards more central collisions at low and intermediate pT (0.5 < pT < 3 GeV/c). The v2 of electrons from heavy-flavour hadron decays at mid-rapidity is found to be similar to the one of muons from heavy-flavour hadron decays at forward rapidity (2.5 < y < 4). The results are described within uncertainties by model calculations including substantial elastic interactions of heavy quarks with an expanding strongly-interacting medium

Production of Σ(1385)± and Ξ(1530)0 in p–Pb collisions at √sNN = 5.02 TeV

The transverse momentum distributions of the strange and double-strange hyperon resonances (Σ(1385)±, Ξ(1530)0) produced in p-Pb collisions at sNN−−−√=5.02 TeV were measured in the rapidity range −0.5<yCMS<0 for event classes corresponding to different charged-particle multiplicity densities, ⟨dNch/dηlab⟩. The mean transverse momentum values are presented as a function of ⟨dNch/dηlab⟩, as well as a function of the particle masses and compared with previous results on hyperon production. The integrated yield ratios of excited to ground-state hyperons are constant as a function of ⟨dNch/dηlab⟩. The equivalent ratios to pions exhibit an increase with ⟨dNch/dηlab⟩, depending on their strangeness content

Suppression of Λ(1520) resonance production in central Pb–Pb collisions at √sNN = 2.76 TeV

The production yield of the Λ(1520) baryon resonance is measured at mid-rapidity in Pb-Pb collisions at sNN−−−√ = 2.76 TeV with the ALICE detector at the LHC. The measurement is performed in the Λ(1520)→pK− (and charge conjugate) hadronic decay channel as a function of the transverse momentum (pT) and collision centrality. The pT-integrated production rate of Λ(1520) relative to Λ in central collisions is suppressed by about a factor of 2 with respect to peripheral collisions. This is the first observation of the suppression of a baryonic resonance at the LHC and the first 3σ evidence of Λ(1520) suppression within a single collision system. The measured Λ(1520)/Λ ratio in central collisions is smaller than the value predicted by the statistical hadronisation model calculations. The shape of the measured pT distribution and the centrality dependence of the suppression are reproduced by the EPOS3 Monte Carlo event generator. The measurement adds further support to the formation of a dense hadronic phase in the final stages of the evolution of the fireball created in heavy-ion collisions, lasting long enough to cause a significant reduction in the observable yield of short-lived resonances