The role of Phragmites australis in carbon, water and energy fluxes from a fen in southwest Germany

The global carbon emission from peat soils adds up to 0.1 Gt-C per year. Under anaerobic conditions, organic material is decomposed to methane (CH4). Over a 100-year cycle, methane is a 28 times stronger greenhouse gas than carbon dioxide and is an important factor for climate change. Therefore, there is a great interest to get a better understanding of the carbon flows in peatlands. Phragmites peatlands are particularly interesting due to the global abundance of this wetland plant (Phragmites australis, common reed) and the highly efficient internal gas transport mechanism. This is a humidity-induced convective flow (HIC) to transport oxygen (O2) to the roots and rhizomes, with the effect that simultaneously soil gases (CH4 and CO2) can be transported to the atmosphere via the plant. Thereby, Phragmites is expected to have a high evapotranspiration (ET) rate due to the large leaf area, open water habitat and high aerodynamic roughness. This ET could highly influence the hydrology of the system. Because he accumulation of organic material occurs because of limiting oxygen levels, hydrological processes are fundamental in the development of peatlands. The research aims were: 1) to clarify the effect of plant-mediated gas transport on CH4 emission, 2) to find out whether Phragmites peatlands are a net source or sink of greenhouse gases, and 3) to evaluate ET in perspective of surface energy partitioning and compare results with FAOs Penman-Monteith equation. CO2, CH4 and latent and sensible energy fluxes were measured with the eddy covariance (EC) technique within a Phragmites-dominated fen in southwest Germany in 2013, 2014 and 2016. In 2016, a field experiment was set up to quantify the contribution of plant-mediated CH4 transport to the overall CH4 flux and how it influences ebullition. One year of EC flux data (March 2013February 2014) shows very clear diurnal and seasonal patterns for both CO2 and CH4. The diurnal pattern of CH4 fluxes was only visible when living green reed was present. This diurnal cycle had the highest correlation with global radiation, which suggests a high influence of HIC on CH4 emission. But if the cause were HIC, relative humidity should correlate stronger with CH4 flux. Therefore, we conclude that in addition to HIC at least one other mechanism must have been involved in the creation of the convective flow within the Phragmites plants. We quantified the influence of pressurized flow within Phragmites on total CH4 emission in a field experiment (see chapter 3) and found between 23% and 45% lower total CH4 flux when pressurized flow was excluded (by cutting or cutting and sealing the reed). The gas transport pathways from the soil to the atmosphere changed as well. Relative contribution of ebullition to the total flux increased from 2% in intact Phragmites to 24-37% in cut vegetation. This increase in ebullition in cut vegetation, obviously, did not compensate the excluded pathway via the pressurized air flow at our site. It also means that the effect of CH4 bypassing the oxic water layer by plant transport on CH4 emission is much larger than the effect of O2 transport through the plants on CH4 oxidation and production in the rhizosphere. Overall, the fen was a sink for carbon and greenhouse gases in the measured year, with a total carbon uptake of 221 g C m-2 yr-1 (26% of the total assimilated carbon). The net uptake of greenhouse gases was 52 g CO2 eq.m-2 yr-1, which is obtained from an uptake of CO2 of 894 g CO2 m-2 yr-1 and a release of CH4 of 842 g CO2 eq.m-2 yr-1. Compared to the long term uptake of carbon by northern peatlands (2050 g C m-2 yr-1) 212 g C yr-1 is therefore very high. One year of measurements is not enough to draw hard conclusions about the climate change impact of this peatland. The measured ET at our site was lower than other Phragmites wetlands in temperate regions. ET was half the amount of precipitation (see chapter 4). Therefore, the risk of the wetland to dry out is not realistic. ET was especially low when there was little plant activity (May and October). Then, the dominant turbulent energy flux was sensible heat not latent heat. This can be explained by the high density of dead reed in these months. the reed heats up causing a high sensible heat flux. Evaporation was low due to the shading of the water layer below the canopy and low wind velocities near the surface. FAOs Penman-Monteith equation was a good estimator of measured ET with crop factors from the regression model of Zhou and Zhou (2009) (see chapter 4). Especially the day-to-day variation was modeled very well. Their model had air temperature, relative humidity and net radiation as input variables. This is likely related to stomatal resistance, which depends on the same variables. Therefore, the model of Zhou and Zhou (2009) is an interesting tool for calculating daily crop factors and it is probably robust enough to be used also in different regions.Die globale Aufnahme von Kohlenstoff in Torfböden beträgt bis zu 0,1 Gt-C pro Jahr. Obwohl dieser Speicher einen positiven Beitrag zur Abschwächung des Klimawandels leistet, wird aufgrund anaerober Bedingungen im Boden, organisches Material zu Methan (CH4) abgebaut. Über einen Zeitraum von hundert Jahren ist CH4 ein um das 28-fache stärkere Treibhausgas als Kohlenstoffdioxid und daher besteht Interesse am Verstehen des Kohlenstoffkreislaufes in Mooren. Schilf-bewachsene Moore (Phragmites-Moore) sind dabei von besonderem Interesse, da der Transport von Sauerstoff (O2) zu den Wurzeln und Rhizomen beruht auf Luftfeuchtigkeit-induzierten konvektiven Fluss (HIC), wobei gleichzeitig auch Bodengase (CH4 und CO2) durch die Pflanze in die Atmosphäre transportiert werden können. Dazu kommt, dass aufgrund der großen Blattfläche, des Lebensraums im offenen Wasser und eine hohen aerodynamischen Rauheit, wird daher erwartet, dass Phragmites eine hohe Evapotranspirationrate (ET) aufweist. Diese ET-rate könnte maßgeblich die Hydrologie des Systems beeinflussen, was grundlegend ist für die Entwicklung von Mooren. Die Forschungsziele waren 1) zu verdeutlichen, welche Rolle der Gastransport durch die Pflanzen auf die CH4-Flüsse hat, 2) ob Phragmites-Moore ein Netto-Quelle oder eine Netto-Senke für Treibhausgase sind und 3) die ET im Hinblick auf Sonnenenergie-Aufteilung zu messen. CO2, CH4, sensible und latente Energieflüsse wurden 2013, 2014 und 2016 mit der Eddy-Kovarianz (EK) Methode in einem von Phragmites dominierten Moor im Südwesten Deutschlands gemessen. 2016 wurde ein Experiment durchgeführt, um den Beitrag des CH4-Transports durch die Pflanzen zum gesamten CH4-Fluss zu quantifizieren und dessen Einfluss auf Ebullition (Bildung von Gasblasen) zu ermitteln. Die EK-Daten eines Jahres zeigen sehr deutliche tageszyklische und saisonale Muster sowohl für CO2 als auch für CH4. Die tageszyklischen CH4-Flüsse waren nur zu erkennen, wenn lebendes Schilf anwesend war und korrelierte am meisten mit der Globalstrahlung. Sollte HIC die Hauptursache sein, müsste eine stärkere Korrelation zwischen relativer Luftfeuchtigkeit festzustellen sein. Da dies nicht der Fall ist, schließen wir, dass es noch mindestens einen weiteren Mechanismus gibt, der in der Erzeugung der Konvektionsströmung innerhalb der Phragmites-Pflanzen involviert ist. In einem Feldexperiment ist quantifiziert, welchen Einfluss die Konvektionsströmung innerhalb der Schilf-Pflanzen auf den gesamten CH4-Fluss hat, und fanden einen zwischen 23% und 45% niedrigeren CH4-Fluss, wenn Konvektionsströmung ausgeschlossen werden konnte, indem das Schilfrohr abgeschnitten, bzw. abgeschnitten und versiegelt wurde. Der relative Beitrag der Ebullition zum gesamten Fluss stieg von 2% bei intaktem Schilfrohr auf 24-37% bei geschnittener Vegetation. Es ist deutlich, dass der Anstieg von Ebullition nicht den verhinderten Gastransport durch die Konvektionsströmung kompensieren konnte. Das Experiment zeigte ebenfalls, dass der Transport von CH4 durch Pflanzen, wobei die sauerstoffhaltige Wasserschicht umgangen wird, einen viel größeren Effekt auf die CH4 Emission hat als die Änderung der CH4-Oxidation und -Produktion in der Rhizosphäre durch den O2 Transport durch die Pflanzen. Insgesamt, war das Moor über das erst gemessene Jahr betrachtet eine Senke für Kohlenstoff (221 g C m-2 yr-1) und Treibhausgase (52 g CO2 eq.m-2 yr-1), wobei 894 g CO2 m-2 yr-1 aufgenommen und 842 g CO2-Äq. m-2 yr-1 CH4 abgegeben wurde. Verglichen mit der langfristigen Aufnahme von Kohlenstoff in nördlichen Mooren (2050 g C m-2 yr-1) ist die Aufnahme von 212 g C yr-1 sehr hoch. Da die Auswertung der Messdaten eines Jahres keine belastbare Schlussfolgerung über den Einfluss dieses Moores auf den Klimawandel zulässt, sollte auch aus den anderen gemessenen Jahren (2014, 2016) die Kohlenstoffbilanz evaluiert werden. Bezüglich der gemessenen ET hat unser Standort eine niedrige ET im Vergleich mit anderen Phragmites Feuchtgebieten im gemäßigten Klima. Besonders in Zeiten geringer Pflanzenaktivität (Mai und Oktober) war die ET sehr gering. Dies kann durch die große Menge an abgestorbenen Schilfrohrpflanzen in diesen Monaten erklärt werden. Während der Entwicklung von Phragmites stieg die Transpiration an und trug maßgeblich zu ET bei. Die Penman-Monteith Gleichung der FAO erwies sich als guter Schätzwert der gemessenen ET, crop factors aus der Literatur verwendet wurden. Eine besonders gute Übereinstimmung ziwschen gemessener und berechneter ET, ergab das Regressionsmodel von Zhou und Zou (2009). Dieses Model verwendet Lufttemperatur, relative Luftfeuchtigkeit und netto Strahlung als Inputvariablen. Wahrscheinlich besteht hier ein Zusammenhang zum stomatären Widerstand. Aus diesem Grund ist das Model von Zhou und Zhou (2009) ein interessantes Werkzeug, um tägliche crop factors zu berechnen. Es ist außerdem robust genug, um in verschiedenen Regionen verwendet zu werden (China im Vergleich zu Deutschland)

Conventional subsoil irrigation techniques do not lower carbon emissions from drained peat meadows

The focus of current water management in drained peatlands is to facilitate optimal drainage, which has led to soil subsidence and a strong increase in greenhouse gas (GHG) emissions. The Dutch land and water authorities proposed the application of subsoil irrigation (SSI) system on a large scale to potentially reduce GHG emissions, while maintaining high biomass production. Based on model results, the expectation was that SSI would reduce peat decomposition in summer by preventing groundwater tables (GWTs) from dropping below −60 cm. In 2017–2018, we evaluated the effects of SSI on GHG emissions (CO2, CH4, N2O) for four dairy farms on drained peat meadows in the Netherlands. Each farm had a treatment site with SSI installation and a control site drained only by ditches (ditch water level −60 / −90 cm, 100 m distance between ditches). The SSI system consisted of perforated pipes −70 cm from surface level with spacing of 5–6 m to improve drainage during winter–spring and irrigation in summer. GHG emissions were measured using closed chambers every 2–4 weeks for CO2, CH4 and N2O. Measured ecosystem respiration (Reco) only showed a small difference between SSI and control sites when the GWT of SSI sites were substantially higher than the control site (&gt; 20 cm difference). Over all years and locations, however, there was no significant difference found, despite the 6–18 cm higher GWT in summer and 1–20 cm lower GWT in wet conditions at SSI sites. Differences in mean annual GWT remained low (&lt; 5 cm). Direct comparison of measured N2O and CH4 fluxes between SSI and control sites did not show any significant differences. CO2 fluxes varied according to temperature and management events, while differences between control and SSI sites remained small. Therefore, there was no difference between the annual gap-filled net ecosystem exchange (NEE) of the SSI and control sites. The net ecosystem carbon balance (NECB) was on average 40 and 30 t CO2 ha−1 yr−1 in 2017 and 2018 on the SSI sites and 38 and 34 t CO2 ha−1 yr−1 in 2017 and 2018 on the control sites. This lack of SSI effect is probably because the GWT increase remains limited to deeper soil layers (60–120 cm depth), which contribute little to peat oxidation. We conclude that SSI modulates water table dynamics but fails to lower annual carbon emission. SSI seems unsuitable as a climate mitigation strategy. Future research should focus on potential effects of GWT manipulation in the uppermost organic layers (−30 cm and higher) on GHG emissions from drained peatlands.</p

Effect of the consumption of a fermented dairy product containing Bifidobacterium lactis DN-173 010 on constipation in childhood: a multicentre randomised controlled trial (NTRTC: 1571)

<p>Abstract</p> <p>Background</p> <p>Constipation is a frustrating symptom affecting 3% of children worldwide. Randomised controlled trials show that both polyethylene glycol and lactulose are effective in increasing defecation frequency in children with constipation. However, in 30–50%, these children reported abdominal pain, bloating, flatulence, diarrhoea, nausea and bad taste of the medication. Two recent studies have shown that the fermented dairy product containing <it>Bifidobacterium lactis </it>strain DN-173 010 is effective in increasing stool frequency in constipation-predominant irritable bowel syndrome patients with a defecation frequency < 3/week and in constipated women with a defecation frequency < 3/week. Goal of this study is to determine whether this fermented dairy product is effective in the treatment of constipated children with a defecation frequency < 3/week.</p> <p>Methods/design</p> <p>It is a two nation (The Netherlands and Poland) double-blind, placebo-controlled randomised multicentre trial in which 160 constipated children (age 3–16 years) with a defecation frequency <3/week will be randomly allocated to consume a fermented dairy product containing <it>Bifidobacterium lactis </it>DN-173 010 or a control product, twice a day, for 3 weeks. During the study all children are instructed to try to defecate on the toilet for 5–10 minutes after each meal (3 times a day) and daily complete a standardized bowel diary. Primary endpoint is stool frequency. Secondary endpoints are stool consistency, faecal incontinence frequency, pain during defecation, digestive symptoms (abdominal pain, flatulence), adverse effects (nausea, diarrhoea, bad taste) and intake of rescue medication (Bisacodyl). Rate of success and rate of responders are also evaluated, with success defined as ≥ 3 bowel movements per week and ≤1 faecal incontinence episode over the last 2 weeks of product consumption and responder defined as a subject reporting a stool frequency ≥ 3 on the last week of product consumption. To demonstrate that the success percentage in the intervention group will be 35% and the success percentage in the control group (acidified milk without ferments, toilet training, bowel diary) will be 15%, with alpha 0.05 and power 80%, a total sample size of 160 patients was calculated.</p> <p>Conclusion</p> <p>This study is aimed to show that the fermented dairy product containing <it>Bifidobacterium lactis </it>strain DN-173 010 is effective in increasing stool frequency after 3 weeks of product consumption in children with functional constipation and a defecation frequency < 3/week.</p

Genome-wide Analyses Identify KIF5A as a Novel ALS Gene

To identify novel genes associated with ALS, we undertook two lines of investigation. We carried out a genome-wide association study comparing 20,806 ALS cases and 59,804 controls. Independently, we performed a rare variant burden analysis comparing 1,138 index familial ALS cases and 19,494 controls. Through both approaches, we identified kinesin family member 5A (KIF5A) as a novel gene associated with ALS. Interestingly, mutations predominantly in the N-terminal motor domain of KIF5A are causative for two neurodegenerative diseases: hereditary spastic paraplegia (SPG10) and Charcot-Marie-Tooth type 2 (CMT2). In contrast, ALS-associated mutations are primarily located at the C-terminal cargo-binding tail domain and patients harboring loss-of-function mutations displayed an extended survival relative to typical ALS cases. Taken together, these results broaden the phenotype spectrum resulting from mutations in KIF5A and strengthen the role of cytoskeletal defects in the pathogenesis of ALS.Peer reviewe

Contribution of plant-induced pressurized flow to CH4 emission from a Phragmites fen

Contains fulltext : 224650.pdf (publisher's version ) (Open Access

The METEOR initiative: the way forward for optimal, worldwide data integration to improve care for RA patients

Pathophysiology and treatment of rheumatic disease

Annual CO₂ Budget Estimation From Chamber-Based Flux Measurements on Intensively Drained Peat Meadows: Effect of Gap-Filling Strategies

Estimating annual CO2 budgets on drained peatlands is important in understanding the significance of CO2 emissions from peatland degradation and evaluating the effectiveness of mitigation techniques. The closed-chamber technique is widely used in combination with gap-filling of CO2 fluxes by parameter fitting empirical models of ecosystem respiration (Reco) and gross primary production (GPP). However, numerous gap-filling strategies are available which are suitable for different circumstances and can result in large variances in annual budget estimates. Therefore, a need for guidance on the selection of gap-filling methodology and its influence on the results exists. Here, we propose a framework of gap-filling methods with four Tiers following increasing model complexity at structural and temporal levels. Tier one is a simple parameter fitting of basic empirical models on an annual basis. Tier two adds structural complexity by including extra environmental factors such as grass height, groundwater level and drought condition. Tier three introduces temporal complexity by separation of annual datasets into seasons. Tier four is a campaign-specific parameter fitting approach, representing highest temporal complexity. The methods were demonstrated on two chamber-based CO2 flux datasets, one of which was previously published. Performance of the empirical models were compared in terms of error statistics. Annual budget estimates were indirectly validated with carbon export values. In conclusion, different gap-filling methodologies gave similar annual estimates but different intra-annual CO2 fluxes, which did not affect the detection of the treatment effects. The campaign-wise gap-filling at Tier four gave the best model performances, while Tier three seasonal gap-filling produced satisfactory results throughout, even under data scarcity. Given the need for more complete carbon balances in drained peatlands, our four-Tier framework can serve as a methodological guidance to the handling of chamber-measured CO2 fluxes, which is fundamental in understanding emissions from degraded peatlands and its mitigation. The performance of models on intra-annual data should be validated in future research with continuous measured CO2 flux data