Interannual variation in seasonal drivers of soil respiration in a semi-arid Rocky Mountain meadow

pre-printSemi-arid ecosystems with annual moisture inputs dominated by snowmelt cover much of the western United States, and a better understanding of their seasonal drivers of soil respiration is needed to predict consequences of climatic change on soil CO2 efflux. We assessed the relative importance of temperature, moisture, and plant phenology on soil respiration during seasonal shifts between cold, wet winters and hot, dry summers in a Rocky Mountain meadow over 3.5 separate growing seasons. We found a consistent, unique pattern of seasonal hysteresis in the annual relationship between soil respiration and temperature, likely representative for this ecosystem type, and driven by (1) continued increase in soil T after summer senescence of vegetation, and (2) reduced soil respiration during cold, wet periods at the beginning versus end of the growing season. The timing of meadow senescence varied between years with amount of cold season precipitation, but on average occurred days before soil temperature peaked in late-summer. Autumn soil respiration was greatest when substantial autumn precipitation events occurred early. Surface CO2 efflux was temporarily decoupled from respiratory production during winter 2006/2007, due to effects of winter surface snow and ice on mediating the diffusion of CO2 from deep soil horizons to the atmosphere. Upon melt of a capping surface ice layer, release of soil-stored CO2 was determined to be 65 g C, or *10 % of the total growing season soil respiration for that year. The shift between soil respiration sources arising from moisture-limited spring plant growth and autumn decomposition indicates that annual mineralization of soil carbon will be less dependent on projected changes in temperature than on future variations in amount and timing of precipitation for this site and similar semiarid ecosystems

Measuring and modelling the isotopic composition of soil respiration: insights from a grassland tracer experiment

The carbon isotopic composition (δ<sup>13</sup>C) of CO<sub>2</sub> efflux (δ<sup>13</sup>C<sub>efflux</sub>) from soil is generally interpreted to represent the actual isotopic composition of the respiratory source (δ<sup>13</sup>C<sub>Rs</sub>). However, soils contain a large CO<sub>2</sub> pool in air-filled pores. This pool receives CO<sub>2</sub> from belowground respiration and exchanges CO<sub>2</sub> with the atmosphere (via diffusion and advection) and the soil liquid phase (via dissolution). Natural or artificial modification of δ<sup>13</sup>C of atmospheric CO<sub>2</sub> (δ<sup>13</sup>C<sub>atm</sub>) or δ<sup>13</sup>C<sub>Rs</sub> causes isotopic disequilibria in the soil-atmosphere system. Such disequilibria generate divergence of δ<sup>13</sup>C<sub>efflux</sub> from δ<sup>13</sup>C<sub>Rs</sub> (termed "disequilibrium effect"). <br><br> Here, we use a soil CO<sub>2</sub> transport model and data from a <sup>13</sup>CO<sub>2</sub>/<sup>12</sup>CO<sub>2</sub> tracer experiment to quantify the disequilibrium between δ<sup>13</sup>C<sub>efflux</sub> and δ<sup>13</sup>C<sub>Rs</sub> in ecosystem respiration. The model accounted for diffusion of CO<sub>2</sub> in soil air, advection of soil air, dissolution of CO<sub>2</sub> in soil water, and belowground and aboveground respiration of both <sup>12</sup>CO<sub>2</sub> and <sup>13</sup>CO<sub>2</sub> isotopologues. The tracer data were obtained in a grassland ecosystem exposed to a δ<sup>13</sup>C<sub>atm</sub> of −46.9 ‰ during daytime for 2 weeks. Nighttime δ<sup>13</sup>C<sub>efflux</sub> from the ecosystem was estimated with three independent methods: a laboratory-based cuvette system, in-situ steady-state open chambers, and in-situ closed chambers. <br><br> Earlier work has shown that the δ<sup>13</sup>C<sub>efflux</sub> measurements of the laboratory-based and steady-state systems were consistent, and likely reflected δ<sup>13</sup>C<sub>Rs</sub>. Conversely, the δ<sup>13</sup>C<sub>efflux</sub> measured using the closed chamber technique differed from these by −11.2 ‰. Most of this disequilibrium effect (9.5 ‰) was predicted by the CO<sub>2</sub> transport model. Isotopic disequilibria in the soil-chamber system were introduced by changing δ<sup>13</sup>C<sub>atm</sub> in the chamber headspace at the onset of the measurements. When dissolution was excluded, the simulated disequilibrium effect was only 3.6 ‰. Dissolution delayed the isotopic equilibration between soil CO<sub>2</sub> and the atmosphere, as the storage capacity for labelled CO<sub>2</sub> in water-filled soil pores was 18 times that of soil air. <br><br> These mechanisms are potentially relevant for many studies of δ<sup>13</sup>C<sub>Rs</sub> in soils and ecosystems, including FACE experiments and chamber studies in natural conditions. Isotopic disequilibria in the soil-atmosphere system may result from temporal variation in δ<sup>13</sup>C<sub>Rs</sub> or diurnal changes in the mole fraction and δ<sup>13</sup>C of atmospheric CO<sub>2</sub>. Dissolution effects are most important under alkaline conditions

Stress Preconditioning of Spreading Depression in the Locust CNS

Cortical spreading depression (CSD) is closely associated with important pathologies including stroke, seizures and migraine. The mechanisms underlying SD in its various forms are still incompletely understood. Here we describe SD-like events in an invertebrate model, the ventilatory central pattern generator (CPG) of locusts. Using K+ -sensitive microelectrodes, we measured extracellular K+ concentration ([K+]o) in the metathoracic neuropile of the CPG while monitoring CPG output electromyographically from muscle 161 in the second abdominal segment to investigate the role K+ in failure of neural circuit operation induced by various stressors. Failure of ventilation in response to different stressors (hyperthermia, anoxia, ATP depletion, Na+/K+ ATPase impairment, K+ injection) was associated with a disturbance of CNS ion homeostasis that shares the characteristics of CSD and SD-like events in vertebrates. Hyperthermic failure was preconditioned by prior heat shock (3 h, 45°C) and induced-thermotolerance was associated with an increase in the rate of clearance of extracellular K+ that was not linked to changes in ATP levels or total Na+/K+ ATPase activity. Our findings suggest that SD-like events in locusts are adaptive to terminate neural network operation and conserve energy during stress and that they can be preconditioned by experience. We propose that they share mechanisms with CSD in mammals suggesting a common evolutionary origin

Surveillance of Transmitted HIV-1 Drug Resistance in Gauteng and KwaZulu-Natal Provinces, South Africa, 2005-2009

Surveillance of human immunodeficiency virus type 1 transmitted drug resistance (TDR) was conducted among pregnant women in South Africa over a 5-year period after the initiation of a large national antiretroviral treatment program. Analysis of TDR data from 9 surveys conducted between 2005 and 2009 in 2 provinces of South Africa suggests that while TDR remains low (<5%) in Gauteng Province, it may be increasing in KwaZulu-Natal, with the most recent survey showing moderate (5%-15%) levels of resistance to the nonnucleoside reverse transcriptase inhibitor drug clas

Cellular responses of Candida albicans to phagocytosis and the extracellular activities of neutrophils are critical to counteract carbohydrate starvation, oxidative and nitrosative stress

Acknowledgments We thank Alexander Johnson (yhb1D/D), Karl Kuchler (sodD/D mutants), Janet Quinn (hog1D/D, hog1/cap1D/D, trx1D/D) and Peter Staib (ssu1D/D) for providing mutant strains. We acknowledge helpful discussions with our colleagues from the Microbial Pathogenicity Mechanisms Department, Fungal Septomics and the Microbial Biochemistry and Physiology Research Group at the Hans Kno¨ll Institute (HKI), specially Ilse D. Jacobsen, Duncan Wilson, Sascha Brunke, Lydia Kasper, Franziska Gerwien, Sea´na Duggan, Katrin Haupt, Kerstin Hu¨nniger, and Matthias Brock, as well as from our partners in the FINSysB Network. Author Contributions Conceived and designed the experiments: PM HW IMB AJPB OK BH. Performed the experiments: PM CD HW. Analyzed the data: PM HW IMB AJPB OK BH. Wrote the paper: PM HW OK AJPB BH.Peer reviewedPublisher PD

Deciding on appropriate use of force: human-machine interaction in weapons systems and emerging norms

This article considers the role of norms in the debate on autonomous weapons systems (AWS). It argues that the academic and political discussion is largely dominated by considerations of how AWS relate to norms institutionalised in international law. While this debate on AWS has produced insights on legal and ethical norms and sounded options of a possible regulation or ban, it neglects to investigate how complex human-machine interactions in weapons systems can set standards of appropriate use of force, which are politically-normatively relevant but take place outside of formal, deliberative law-setting. While such procedural norms are already emerging in the practice of contemporary warfare, the increasing technological complexity of AI-driven weapons will add to their political-normative relevance. I argue that public deliberation about and political oversight and accountability of the use of force is at risk of being consumed and normalised by functional procedures and perceptions. This can have a profound impact on future of remote-warfare and security policy

The association between human endogenous retroviruses and multiple sclerosis: a systematic review and meta-analysis

Background: The interaction between genetic and environmental factors is crucial to multiple sclerosis (MS) pathogenesis. Human Endogenous Retroviruses (HERVs) are endogenous viral elements of the human genome whose expression is associated with MS. Objective: To perform a systematic review and meta-analysis and to assess qualitative and quantitative evidence on the expression of HERV families in MS patients. Methods: Medline, Embase and the Cochrane Library were searched for published studies on the association of HERVs and MS. Meta-analysis was performed on the HERV-W family. Odds Ratio (OR) and 95% confidence interval (CI) were calculated for association. Results: 43 reports were extracted (25 related to HERV-W, 13 to HERV-H, 9 to HERV-K, 5 to HRES-1 and 1 to HER-15 family). The analysis showed an association between expression of all HERV families and MS. For HERV-W, adequate data was available for meta-analysis. Results from meta-analyses of HERV-W were OR = 22.66 (95%CI 6.32 to 81.20) from 4 studies investigating MSRV/HERV-W(MS-associated retrovirus) envelope mRNA in peripheral blood mononuclear cells, OR = 44.11 (95%CI 12.95 to 150.30) from 6 studies of MSRV/ HERV-W polymerase mRNA in serum/plasma and OR = 6.00 (95%CI 3.35 to 10.74) from 4 studies of MSRV/HERV-W polymerase mRNA in CSF

Incorporation of uranium into hematite during crystallization from ferrihydrite

Ferrihydrite was exposed to U(VI)-containing cement leachate (pH 10.5) and aged to induce crystallization of hematite. A combination of chemical extractions, TEM, and XAS techniques provided the first evidence that adsorbed U(VI) (≈3000 ppm) was incorporated into hematite during ferrihydrite aggregation and the early stages of crystallization, with continued uptake occurring during hematite ripening. Analysis of EXAFS and XANES data indicated that the U(VI) was incorporated into a distorted, octahedrally coordinated site replacing Fe(III). Fitting of the EXAFS showed the uranyl bonds lengthened from 1.81 to 1.87 Å, in contrast to previous studies that have suggested that the uranyl bond is lost altogether upon incorporation into hematite the results of this study both provide a new mechanistic understanding of uranium incorporation into hematite and define the nature of the bonding environment of uranium within the mineral structure. Immobilization of U(VI) by incorporation into hematite has clear and important implications for limiting uranium migration in natural and engineered environments. © 2014 American Chemical Society

Population-Related Variation in Plant Defense more Strongly Affects Survival of an Herbivore than Its Solitary Parasitoid Wasp

The performance of natural enemies, such as parasitoid wasps, is affected by differences in the quality of the host’s diet, frequently mediated by species or population-related differences in plant allelochemistry. Here, we compared survival, development time, and body mass in a generalist herbivore, the cabbage moth, Mamestra brassicae, and its solitary endoparasitoid, Microplitis mediator, when reared on two cultivated (CYR and STH) and three wild (KIM, OH, and WIN) populations of cabbage, Brassica oleracea. Plants either were undamaged or induced by feeding of larvae of the cabbage butterfly, Pieris rapae. Development and biomass of M. brassicae and Mi. mediator were similar on both cultivated and one wild cabbage population (KIM), intermediate on the OH population, and significantly lower on the WIN population. Moreover, development was prolonged and biomass was reduced on herbivore-induced plants. However, only the survival of parasitized hosts (and not that of healthy larvae) was affected by induction. Analysis of glucosinolates in leaves of the cabbages revealed higher levels in the wild populations than cultivars, with the highest concentrations in WIN plants. Multivariate statistics revealed a negative correlation between insect performance and total levels of glucosinolates (GS) and levels of 3-butenyl GS. However, GS chemistry could not explain the reduced performance on induced plants since only indole GS concentrations increased in response to herbivory, which did not affect insect performance based on multivariate statistics. This result suggests that, in addition to aliphatic GS, other non-GS chemicals are responsible for the decline in insect performance, and that these chemicals affect the parasitoid more strongly than the host. Remarkably, when developing on WIN plants, the survival of Mi. mediator to adult eclosion was much higher than in its host, M. brassicae. This may be due to the fact that hosts parasitized by Mi. mediator pass through fewer instars, and host growth is arrested when they are only a fraction of the size of healthy caterpillars. Certain aspects of the biology and life-history of the host and parasitoid may determine their response to chemical challenges imposed by the food plant