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Nitrogen effect on molecular dynamics in forest soils (end of thesis)

English title Nitrogen effect on molecular dynamics in forest soils (end of thesis)
Applicant Schmidt Michael W. I.
Number 146850
Funding scheme Project funding (Div. I-III)
Research institution Geographisches Institut Universität Zürich
Institution of higher education University of Zurich - ZH
Main discipline Pedology
Start/End 01.05.2013 - 30.04.2014
Approved amount 58'236.00
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All Disciplines (2)

Discipline
Pedology
Geochemistry

Keywords (10)

liquid chromatography; plant biomarkers; amino sugars; fatt acids; fungal biomarkers; CO2 fumigation; compound-specific isotope analysis; forest soil; microbial biomarkers; nitrogen deposition

Lay Summary (German)

Lead
Menschliches Handeln beeinflusst Ökosysteme auf verschiedenste Weisen. Eine davon ist die chronische atmosphärische Deposition von reaktivem Stickstoff in Wäldern. Aber inwiefern beeinflusst diese künstliche Düngung wichtige Ökosystemdienstleistungen, wie etwa die Fähigkeit des Bodens, organischen Kohlenstoff zu speichern?
Lay summary

Emissionen aus der Verbrennung von fossilen Energieträgern haben den Ausstoss von reaktiven Stickstoffverbindungen in die Atmosphäre während der letzten Jahrzehnte stark erhöht. Da es sich bei Stickstoff um den wichtigsten Pflanzennährstoff handelt, resultiert die erhöhte Stickstoffdeposition in einer Düngung von Ökosystemen über die Atmosphäre. Es wurde angenommen, dass diese Düngung zu verstärktem Baumwachstum führt und damit Kohlenstoffdioxid aus der Atmosphäre entzogen wird, was durchaus ein positiver Effekt wäre. Allerdings ist der meiste Kohlenstoff der Wälder nicht in Bäumen gespeichert, sondern im Boden. Erhöhte Stickstoffzugaben können die Aktivität von Abbauorganismen im Boden steigern und damit zu erhöhter Produktion von Kohlenstoffdioxid und schliesslich zu Verlust von Bodenkohlenstoff führen. Mitunter wurden auch gegensätzliche Effekte von Stickstoffgaben auf den Bodenkohlenstoff beobachtet. Die Ursachen für diese unterschiedlichen Effekte von Stickstoff auf den Bodenkohlenstoff werden jedoch noch nicht verstanden.

In diesem Projekt wollen wir die Hypothese testen, dass der Stickstoffeffekt auf den Bodenkohlenstoff mit der Qualität der organischen Bodensubstanz variiert. Kohlenstoff ist im Boden in der organischen Bodensubstanz gespeichert, welche hauptsächlich von Pflanzenstreu und mikrobiellen Rückständen stammt. Diese unterscheiden sich in ihrer chemischen Zusammensetzung voneinander. Ein bedeutender Unterschied ist der Stickstoffgehalt, welcher in Mikroorganismen viel höher ist als in Pflanzen. Die stickstoffreiche organische Substanz der Mikroorganismen könnte anders auf Stickstoffdeposition reagieren als die stickstoffarme Pflanzenstreu. 

Direct link to Lay Summary Last update: 21.04.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Interactive effects of elevated CO2 and nitrogen deposition on fatty acid molecular and isotope composition of above- and belowground tree biomass and forest soil fractions
Griepentrog M. Eglinton T. I. Hagedorn F. Schmidt M. W. Wiesenberg G. L. (2015), Interactive effects of elevated CO2 and nitrogen deposition on fatty acid molecular and isotope composition of above- and belowground tree biomass and forest soil fractions, in Global Change Biology, 21(1), 473-486.
Nitrogen deposition promotes the production of new fungal residues but retards the decomposition of old residues in forest soil fractions
Griepentrog Marco, Bodé Samuel, Boeckx Pascal, Hagedorn Frank, Heim Alexander, Schmidt Michael W. I. (2014), Nitrogen deposition promotes the production of new fungal residues but retards the decomposition of old residues in forest soil fractions, in Global Change Biology, 20(1), 327-340.
Discrepancies in utilization of density fractionation along with ultrasonic dispersion to obtain distinct pools of soil organic matter
Griepentrog Marco, Schmidt Michael W. I. (2013), Discrepancies in utilization of density fractionation along with ultrasonic dispersion to obtain distinct pools of soil organic matter, in Journal of Plant Nutrition and Soil Science, 176(4), 500-504.

Collaboration

Group / person Country
Types of collaboration
Prof. Dr. Pascal Boeckx (Isotope Bioscience Laboratory, Ghent University) Belgium (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Prof. Dr. Timothy I. Eglinton (Biogeoscience Group, Geological Institute, ETH Zurich) Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
26th International Meeting on Organic Geochemistry (IMOG), September 2013 in Tenerife, Spain Poster No effects of increased nitrogen deposition on the composition and turnover of plant and microbial biomarkers in forest soil density fractions. 01.09.2013 Costa Adeje (Tenerife), Spain Hagedorn Frank; Schmidt Michael W. I.; Griepentrog Marco;


Associated projects

Number Title Start Funding scheme
112021 Umsatz der organischen Substanz in Waldböden unter erhöhtem N-Eintrag: In situ Tracerversuche mit 13C und 15N markierter Buchenstreu 01.01.2007 Project funding (Div. I-III)
172744 DEEP C 01.10.2017 Project funding (Div. I-III)
126778 Nitrogen effect on molecular dynamics in forest soils 01.05.2010 Project funding (Div. I-III)
126778 Nitrogen effect on molecular dynamics in forest soils 01.05.2010 Project funding (Div. I-III)

Abstract

Atmospheric nitrogen deposition affects many forests and their ecosystem functions, including organic matter cycling in soils of temperate forests. But it is not clear how, and what the underlying mechanisms are. Here we asked the question: Do compounds with high intrinsic nitrogen content (typical for microbially-derived biomass) respond differently to atmospheric nitrogen deposition than compounds with low nitrogen content (such as plant-derived biomass)?Two facts delayed the progress of the project in the first year. From May 2010 to June 2011 the PhD student Marco Griepentrog successfully completed make-up classes for the recognition of his Fachhochschule degree by the University of Zurich. His workload (30 credit points or 900 working hours) was 50% of the annual workload of a full time student, and delayed the progress of the project. Furthermore the PI Dr. Alexander Heim has left research in November 2010 and started a new position in industry and the co-PI Prof. Michael Schmidt stepped in as PI.Despite the delay the project eventually progressed well thanks to the hard-working PhD student Marco Griepentrog, who worked in the lab and simultaneously compiled a detailed methodological literature review on preparative soil fractionation procedures. His review revealed striking discrepancies in the application of this frequently used method, and was submitted to a peer-reviewed journal and is still under revision. With a competitive travel grant from the European Science Foundation, Marco Griepentrog worked at the University of Ghent (Belgium) and could measure compound-specific isotope ratios of amino sugars reliable in soil density fractions for the first time, using a novel analytical technique. This was the first time that amino sugars were measured in density fractions, and we could show that especially bacterial amino sugars were associated with soil minerals. Furthermore, when combined with stable isotope labeling, it became evident that amino sugar turn over much slower when associated with soil minerals. Another unexpected result was that fungal residues turn over at the same rate as total organic carbon, while bacterial amino sugars turn over slower. The fact that fungal amino sugars turn over faster than bacterial amino sugars contradicts with previous assumptions, and our measurements are the first to show that. Results have been presented at several international conferences, and now a manuscript circulates between co-authors to be submitted to a high impact scientific journal later this year. For the final year, we plan to focus on another compound class and propose a change of the initially planned target compound lignin. Own results showed that the isotopic label might not be detectable in lignin but in fatty acids, since they have been shown to turnover faster. Also the analysis of fatty acids is more precise and less labor intensive. Moreover, the analysis of lignin is not possible at the formerly intended laboratory, but we found new analytical opportunities to analyze fatty acids. Additionally, a worldwide known expert in fatty acid analysis recently joined our group and the project outcome will certainly benefit from his expertise. Here we ask for a fourth year of the PhD project (May 2013 to April 2014). The focus would be to finish the measurements outlined below, present the results at two international meetings (April and September 2013), finalize the third manuscript, write the thesis and submit it until February 2014 so that it could be defended in April 2014.
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