Tree species effects on soil microbial community composition and greenhouse gases emissions in a Mediterranean ecotone forest

Resumen de una presentación realizada en: I Simposio sobre Interacciones Planta-Suelo (ICA-CSIC, Madrid, 25-26 Febrero 2016)Over recent decades in the Iberian Peninsula, altitudinal shifts from Pinus sylvestris L. to Quercus pyrenaica Willd species has been observed as a consequence of Global Change, meaning changes in temperature, precipitation, land use and forestry. The forest conversion from pine to oak can alter the litter quality and quantity provided to the soil and thereby the soil microbial community composition and functioning. Since soil microbiota plays an important role in organic matter decomposition, and this in turn is key in biogeochemical cycles and forest ecosystems productivity, the rate in which forests produce and consume greenhouse gases can be also affected by changes in forest composition. In other words, changes in litter decomposition will ultimately affect downstream carbon and nitrogen dynamics although this impact is uncertain. In order to predict changes in carbon and nitrogen stocks in Global Change scenarios, it is necessary to deepen the impact of vegetation changes on soil microbial communities, litter decomposition dynamics (priming effect) and the underlying interactions between these factors. To test this, we conducted a full-factorial transplant microcosms experiment mixing both fresh soils and litter from Pyrenean oak, Scots pine and mixed stands collected inside their transitional area in Central Spain. The microcosms consisted in soil cylinders inside Kilner jars used as chambers inside an incubator. In this experiment, we investigated how and to what extent the addition of litter with different quality (needles, oak leaves and mixed needlesleaves) to soil inoculums with contrasting soil microbiota impact on soil (i) CO2, NO, N2O and CH4 efflux rates, (ii) total organic carbon and nitrogen and (iii) dissolved organic carbon and nitrogen. Furthermore, we assessed if these responses were controlled by changes in the microbial community structure using the PLFA analyses prior and after the incubation period of 54 days.Peer reviewe

Soil respiration at mean annual temperature predicts annual total across vegetation types and biomes

Soil respiration (SR) constitutes the largest flux of CO₂ from terrestrial ecosystems to the atmosphere. However, there still exist considerable uncertainties as to its actual magnitude, as well as its spatial and interannual variability. Based on a reanalysis and synthesis of 80 site-years for 57 forests, plantations, savannas, shrublands and grasslands from boreal to tropical climates we present evidence that total annual SR is closely related to SR at mean annual soil temperature (〖SR〗_MAT), irrespective of the type of ecosystem and biome. This is theoretically expected for non water-limited ecosystems within most of the globally occurring range of annual temperature variability and sensitivity (Q₁₀). We further show that for seasonally dry sites where annual precipitation (P) is lower than potential evapotranspiration (PET), annual SR can be predicted from wet season SRMAT corrected for a factor related to P/PET. Our finding indicates that it can be sufficient to measure 〖SR〗_MAT for obtaining a well constrained estimate of its annual total. This should substantially increase our capacity for assessing the spatial distribution of soil CO₂ emissions across ecosystems, landscapes and regions, and thereby contribute to improving the spatial resolution of a major component of the global carbon cycle

Habitat Fragmentation can Modulate Drought Effects on the Plant-soil-microbial System in Mediterranean Holm Oak (Quercus ilex) Forests

© 2015, Springer Science+Business Media New York. Ecological transformations derived from habitat fragmentation have led to increased threats to above-ground biodiversity. However, the impacts of forest fragmentation on soils and their microbial communities are not well understood. We examined the effects of contrasting fragment sizes on the structure and functioning of soil microbial communities from holm oak forest patches in two bioclimatically different regions of Spain. We used a microcosm approach to simulate the annual summer drought cycle and first autumn rainfall (rewetting), evaluating the functional response of a plant-soil-microbial system. Forest fragment size had a significant effect on physicochemical characteristics and microbial functioning of soils, although the diversity and structure of microbial communities were not affected. The response of our plant-soil-microbial systems to drought was strongly modulated by the bioclimatic conditions and the fragment size from where the soils were obtained. Decreasing fragment size modulated the effects of drought by improving local environmental conditions with higher water and nutrient availability. However, this modulation was stronger for plant-soil-microbial systems built with soils from the northern region (colder and wetter) than for those built with soils from the southern region (warmer and drier) suggesting that the responsiveness of the soil-plant-microbial system to habitat fragmentation was strongly dependent on both the physicochemical characteristics of soils and the historical adaptation of soil microbial communities to specific bioclimatic conditions. This interaction challenges our understanding of future global change scenarios in Mediterranean ecosystems involving drier conditions and increased frequency of forest fragmentation

Apoptosis, toll-like, RIG-I-like and NOD-like receptors are pathways jointly induced by diverse respiratory bacterial and viral pathogens

Lower respiratory tract infections are among the top five leading causes of human death. Fighting these infections is therefore a world health priority. Searching for induced alterations in host gene expression shared by several relevant respiratory pathogens represents an alternative to identify new targets for wide-range host-oriented therapeutics. With this aim, alveolar macrophages were independently infected with three unrelated bacterial (Streptococcus pneumoniae, Klebsiella pneumoniae, and Staphylococcus aureus) and two dissimilar viral (respiratory syncytial virus and influenza A virus) respiratory pathogens, all of them highly relevant for human health. Cells were also activated with bacterial lipopolysaccharide (LPS) as a prototypical pathogen-associated molecular pattern. Patterns of differentially expressed cellular genes shared by the indicated pathogens were searched by microarray analysis. Most of the commonly up-regulated host genes were related to the innate immune response and/or apoptosis, with Toll-like, RIG-I-like and NOD-like receptors among the top 10 signaling pathways with over-expressed genes. These results identify new potential broad-spectrum targets to fight the important human infections caused by the bacteria and viruses studied here.The authors gratefully acknowledge financial support from the “CIBER de Enfermedades Respiratorias” (CIBERES), an initiative of the “Instituto de Salud Carlos III” (ISCIII), Spain. Research activities in the participating laboratories received further funding from the following sources: Centro Nacional de Microbiología, ISCIII, PI15CIII/00024 and MINECO (SAF2015- 67033-R); Centro Nacional de Biotecnología, MINECO (BFU2014-57797-R); Hospital Universitari Germans Trias I Pujol, Spanish Society of Pneumology and Thoracic Surgery (SEPAR 054/2011); Departamento de Bioquímica y Biología Molecular I, MINECO (SAF2015-65307-R); Centro de Investigaciones Biológicas, MINECO (SAF2012-39444-C01/02); Fundación de Investigación Sanitaria de las Islas Baleares, MINECO (SAF2012-39841); Instituto de Agrobiotecnología, MINECO (SAF2015-66520-R); Instituto de Química Física Rocasolano, MINECO (BFU2015-70052-R) and the Marie Curie Initial Training Network GLYCOPHARM (PITN-GA- 2012-317297). Subprograma Estatal de Formación (BES-2013- 065355)

Geoeconomic variations in epidemiology, ventilation management, and outcomes in invasively ventilated intensive care unit patients without acute respiratory distress syndrome: a pooled analysis of four observational studies

Background: Geoeconomic variations in epidemiology, the practice of ventilation, and outcome in invasively ventilated intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) remain unexplored. In this analysis we aim to address these gaps using individual patient data of four large observational studies. Methods: In this pooled analysis we harmonised individual patient data from the ERICC, LUNG SAFE, PRoVENT, and PRoVENT-iMiC prospective observational studies, which were conducted from June, 2011, to December, 2018, in 534 ICUs in 54 countries. We used the 2016 World Bank classification to define two geoeconomic regions: middle-income countries (MICs) and high-income countries (HICs). ARDS was defined according to the Berlin criteria. Descriptive statistics were used to compare patients in MICs versus HICs. The primary outcome was the use of low tidal volume ventilation (LTVV) for the first 3 days of mechanical ventilation. Secondary outcomes were key ventilation parameters (tidal volume size, positive end-expiratory pressure, fraction of inspired oxygen, peak pressure, plateau pressure, driving pressure, and respiratory rate), patient characteristics, the risk for and actual development of acute respiratory distress syndrome after the first day of ventilation, duration of ventilation, ICU length of stay, and ICU mortality. Findings: Of the 7608 patients included in the original studies, this analysis included 3852 patients without ARDS, of whom 2345 were from MICs and 1507 were from HICs. Patients in MICs were younger, shorter and with a slightly lower body-mass index, more often had diabetes and active cancer, but less often chronic obstructive pulmonary disease and heart failure than patients from HICs. Sequential organ failure assessment scores were similar in MICs and HICs. Use of LTVV in MICs and HICs was comparable (42\ub74% vs 44\ub72%; absolute difference \u20131\ub769 [\u20139\ub758 to 6\ub711] p=0\ub767; data available in 3174 [82%] of 3852 patients). The median applied positive end expiratory pressure was lower in MICs than in HICs (5 [IQR 5\u20138] vs 6 [5\u20138] cm H2O; p=0\ub70011). ICU mortality was higher in MICs than in HICs (30\ub75% vs 19\ub79%; p=0\ub70004; adjusted effect 16\ub741% [95% CI 9\ub752\u201323\ub752]; p<0\ub70001) and was inversely associated with gross domestic product (adjusted odds ratio for a US$10 000 increase per capita 0\ub780 [95% CI 0\ub775\u20130\ub786]; p<0\ub70001). Interpretation: Despite similar disease severity and ventilation management, ICU mortality in patients without ARDS is higher in MICs than in HICs, with a strong association with country-level economic status. Funding: No funding

Hyperoxemia and excess oxygen use in early acute respiratory distress syndrome : Insights from the LUNG SAFE study

Publisher Copyright: © 2020 The Author(s). Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Background: Concerns exist regarding the prevalence and impact of unnecessary oxygen use in patients with acute respiratory distress syndrome (ARDS). We examined this issue in patients with ARDS enrolled in the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study. Methods: In this secondary analysis of the LUNG SAFE study, we wished to determine the prevalence and the outcomes associated with hyperoxemia on day 1, sustained hyperoxemia, and excessive oxygen use in patients with early ARDS. Patients who fulfilled criteria of ARDS on day 1 and day 2 of acute hypoxemic respiratory failure were categorized based on the presence of hyperoxemia (PaO2 > 100 mmHg) on day 1, sustained (i.e., present on day 1 and day 2) hyperoxemia, or excessive oxygen use (FIO2 ≥ 0.60 during hyperoxemia). Results: Of 2005 patients that met the inclusion criteria, 131 (6.5%) were hypoxemic (PaO2 < 55 mmHg), 607 (30%) had hyperoxemia on day 1, and 250 (12%) had sustained hyperoxemia. Excess FIO2 use occurred in 400 (66%) out of 607 patients with hyperoxemia. Excess FIO2 use decreased from day 1 to day 2 of ARDS, with most hyperoxemic patients on day 2 receiving relatively low FIO2. Multivariate analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FIO2 use and adverse clinical outcomes. Mortality was 42% in patients with excess FIO2 use, compared to 39% in a propensity-matched sample of normoxemic (PaO2 55-100 mmHg) patients (P = 0.47). Conclusions: Hyperoxemia and excess oxygen use are both prevalent in early ARDS but are most often non-sustained. No relationship was found between hyperoxemia or excessive oxygen use and patient outcome in this cohort. Trial registration: LUNG-SAFE is registered with ClinicalTrials.gov, NCT02010073publishersversionPeer reviewe

Functional antagonism between nitrogen-fixing leguminous trees and calcicole-drought-tolerant trees in the Cerrado

The Cerrado is the largest savanna of South America and its physiognomy varies from savanna to woodlands. There are two main types of woodlands in the Cerrado: dystrophic woodlands, dominated by N-fixing leguminous trees (LEG), and mesotrophic woodlands dominated by non-leguminous drought-tolerant trees (DRY), which are calcicoles and sensitive to Al The working hypothesis is that LEG and DRY are functional antagonists in terms of the acidification/alkalization processes involving different forms of inorganic nitrogen and pH, Ca and Al in soil. Tree species basal area and soil properties were used to investigate the antagonism between LEG and DRY using generalized linear models. The results suggest that LEG and DRY are antagonists. The LEG were positively associated with Al, NO and NH4+ content and negatively related to increasing Ca content, whereas the DRY were negatively associated with Al, NO and NH4+ and positively associated with increasing Ca content. The upper soil layer in plots dominated by LEG species became more acidic and the upper soil layer in plots dominated by DRY species became more alkaline. The results suggest that LEG and DRY are functional antagonists and their preferences for NH or NO might influence the way the Cerrado woodland changes.Peer Reviewe