Measurement and modelling of N2O and CH4 emissions from soils

While a lot of work has been done on the methodologies of measuring and estimating terrestrial trace gas emissions, there are still some open fundamental questions. This thesis explores some of these questions. Its scope is necessarily limited to the techniques that have been applied within the course of this work. The studies involving N20 were supported in part by a MAFF (Ministry of Agriculture, Fisheries and Food) funded project on quantifying emissions from fertilised agricultural soils (Grant No. CC0214). All studies involving CH4 and rice plants were part of the EC funded RICEOTOPES project (Grant No. CT97-0408), looking into fluxes and isotopic signatures of CH4 from rice paddies.After the literature review (Chapter I), issues related to the so-called closed chamber technique are investigated in Chapters II and III This is a method, which involves the covering o f a small area (usually < 1 m2) with some type of inverted container and the monitoring of the changing gas concentrations within the headspace so created. While N 20 was used as a target gas in the work described in these chapters, the results are also applicable to other gases. Chapter IV explores the possibility of predicting N 20 emissions through related soil parameters. A simple model has been developed on the basis of closed chamber measurements and the simultaneous measurement of related soil water and mineral N contents, and temperature. This was then verified against data sets obtained by the same methods. Chapter V describes an automated system of closed chambers for the measurement of CH4 from rice paddies and results obtained with this system over two growing seasons. It includes some technical aspects and an illustration of seasonal variability and variations in the pathways of CH4 emission. Chapters VI and VII investigate two possibilities of measuring CH4 from rice on a larger scale than it is possible with closed chambers.In a general discussion, the different approaches to estimating trace gas emissions from land surfaces previously discussed are compared and an outlook on possible future developments is given

Do increasingly depleted δ15N values of atmospheric N2O indicate a decline in soil N2O reduction?

Growing concentrations of N2O within the atmosphere have been accompanied by decreasing δ15N values, provoking the hypothesis of a global decline in the rate of N2O reduction relative to its production in soil. We estimate that the ratio of N2O produced to N2O reduced within the soil profile has declined by about 10-25% relative to its pre-industrial value. To a smaller extent, a reduction in the uptake of atmospheric N2O at the soil surface relative to its emission could also have contributed to the reported isotopic signal. This calls for a greater consideration of the process of N2O reduction in soil and its role in the global turnover of N2

Evidence for Nearly Complete Decoupling of Very Stable Nocturnal Boundary Layer Overland

Concentrations of 222Rn at 0.1m and 6.5m height above ground level and 222Rn flux density were measured during nights characterized by strong cooling, light winds and clear sky conditions in the Carpathian Basin in Hungary. A very stable boundary layer (vSBL) formed on 14 nights between 15 August and 3 September 2009. On 12 nights, an estimated 72% (s.d. 20%) of 222Rn emitted from the surface since sunset was retained within the lowest 6.5m above the ground until sunrise the following morning. On two nights an intermittent increase in wind speed at 9.4m height was followed by a rise in temperature at 2.0m height, indicating a larger atmospheric motion that resulted in 222Rn at 0.1m around sunrise being the same as around the preceding sunset. It does not seem to be rare in a large continental basin for a vSBL to be nearly completely decoupled from the atmosphere above for the entire period from sunset to sunris

Evidence for Nearly Complete Decoupling of Very Stable Nocturnal Boundary Layer Overland

Concentrations of (222)Rn at 0.1 m and 6.5 m height above ground level and (222)Rn flux density were measured during nights characterized by strong cooling, light winds and clear sky conditions in the Carpathian Basin in Hungary. A very stable boundary layer (vSBL) formed on 14 nights between 15 August and 3 September 2009. On 12 nights, an estimated 72% (s.d. 20%) of (222)Rn emitted from the surface since sunset was retained within the lowest 6.5 m above the ground until sunrise the following morning. On two nights an intermittent increase in wind speed at 9.4 m height was followed by a rise in temperature at 2.0 m height, indicating a larger atmospheric motion that resulted in (222)Rn at 0.1 m around sunrise being the same as around the preceding sunset. It does not seem to be rare in a large continental basin for a vSBL to be nearly completely decoupled from the atmosphere above for the entire period from sunset to sunrise. © 2011, Springer. The original publication is available at www.springerlink.co

Der Einfluss symbiotischer Bodenpilze auf den Stickstoffzyklus

To increase nutrient use efficiency and reduce nutrient losses are key aspects for sustainable agriculture. Arbuscular mycorrhizal fungi (AMF) are an import and widespread group of plant-symbiotic soil fungi. Here we investigate the role of those soil microorganisms, for effective nutrient recycling. We conducted greenhouse and lysimeter experiments to compare the cycling of important plant nutrients in systems with high and low abundance of AMF. AMF increased plant N nutrition, reduced leaching losses of mineral N, and prevented emissions of N2O, an important greenhouse gas. The results show the importance of AMF for an effective nutrient management. Farmers should implement strategies to promote AMF in the soil, as they are an indispensable compound of sustainable agriculture

Emission und Aufnahme von Lachgas und Methan durch Ackerböden in der Fruchtfolgesequenz Kunstwiese – Silomais unter konventioneller und biologischer Bewirtschaftung

Organic farming systems provide multiple environmental benefits. Concerning climate change they have a substantial mitigation potential. Skinner et al. (2014) evaluated with Meta-Analysis the global dataset on comparative field measurements of soil greenhouse gas (GHG) fluxes under organic and non-organic agricultural management that have been published by the end of 2012. They showed that for arable land-use under organic management compared to non-organic 1) the cumulated area-scaled N2O emissions are about 15 % lower, 2) yield-scaled N2O emissions are slightly higher and 3) CH4 uptake is higher. However, this database is thin and further field measurements covering whole crop rotations are needed to close knowledge gaps. Therefore soil GHG fluxes are measured since August 2012 in the DOK long-term experiment. Thereby the findings of the Meta-Analysis serve as hypotheses. The measurement results from a grass-clover - maize crop sequence confirm the hypotheses one and three. However hypothesis two was significantly rejected by the biodynamic system compared to the conventional system with farmyard manure

Long-Term Results After Drug-Eluting Versus Bare-Metal Stent Implantation in Saphenous Vein Grafts: Randomized Controlled Trial

Background Efficacy data on drug-eluting stents (DES) versus bare-metal stents (BMS) in saphenous vein grafts are controversial. We aimed to compare DES with BMS among patients undergoing saphenous vein grafts intervention regarding long-term outcome. Methods and Results In this multinational trial, patients were randomized to paclitaxel-eluting or BMS. The primary end point was major adverse cardiac events (cardiac death, nonfatal myocardial infarction, and target-vessel revascularization at 1 year. Secondary end points included major adverse cardiac events and its individual components at 5-year follow-up. One hundred seventy-three patients were included in the trial (89 DES versus 84 BMS). One-year major adverse cardiac event rates were lower in DES compared with BMS (2.2% versus 16.0%, hazard ratio, 0.14; 95% CI, 0.03-0.64,; P; =0.01), which was mainly driven by a reduction of subsequent myocardial infarctions and need for target-vessel revascularization. Five-year major adverse cardiac event rates remained lower in the DES compared with the BMS arm (35.5% versus 56.1%, hazard ratio, 0.40; 95% CI, 0.23-0.68,; P; <0.001). A landmark-analysis from 1 to 5 years revealed a persistent benefit of DES over BMS (hazard ratio, 0.33; 95% CI, 0.13-0.74,; P; =0.007) in terms of target-vessel revascularization. More patients in the BMS group underwent multiple target-vessel revascularization procedures throughout the study period compared with the DES group (DES 1.1% [n=1] versus BMS 9.5% [n=8],; P; =0.013). Enrollment was stopped before the target sample size of 240 patients was reached. Conclusions In this randomized controlled trial with prospective long-term follow-up of up to 5 years, DES showed a better efficacy than BMS with sustained benefits over time. DES may be the preferred strategy in this patient population. Registration URL: https://www.clini​caltr​ials.gov; Unique identifier: NCT00595647