Competition for N in forest soils: stabilization of organic N in recalcitrant pools
Final Report Abstract
The overall intention of this project was to research on the partitioning and key stabilization processes for nitrogen (N) in soil organic matter (SOM) as part of the competition for N in the beech-soil system of a broadleaf forest in Central Europe. Our approach contained two field experiments assessing N stabilization and turnover by using 15N isotope labeling and a laboratory experiment researching on the mineralization behavior of diverse soil fractions. We acquired comprehensive data with these studies and identified specific N fractions and their turnover under special emphasize of climatic impacts induced by climate change. The leaf litter experiment investigated the decomposition of dead plant material and the incorporation of N from labeled beech leaf litter to functional SOM fractions in a Rendzic Leptosol. Our second field experiment targeted the central purpose of the project: We simulated a summer drought as projected by future climate change conditions and evaluated its influence on soil N processing and stabilization in organo-mineral fractions. Our third study accomplished in a laboratory incubation considered simultaneously carbon (C) and N dynamics as deduced from particle size fractions. All experiments used the same soil material from the Research Station near Tuttlingen. These three investigations showed that organo-mineral associations feature prominently in the stabilization of N in the studied soil. The clay fractions are the main sink for N. Light fractions conduce as a transitory pool with short-term passage for N and are reliant on aggregate turnover. With a higher frequency of extended summer droughts in the course of climate change in Central Europe, stabilization patterns will change: N stabilization in organo-mineral associations will be decelerated and N will stay longer in more labile fractions, always at the risk of leaching losses under predicted heavy precipitation events. Our data further discovered that the accessibility of soil organic matter controlled microbial biomass and an effective C mineralization. The C/N ratio as a key performance indicator for biological decomposability, which is often used to distinguish humus forms, is not appropriate to characterize the clay fraction. Despite a greater accessibility and released salt-extractable organic C (SEOC) liberated by the fractionation process, the break-up of the soil structure during fractionation did not impact C mineralization but diminished N mineralization.
Publications
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(2011): Stabilisierung von organischem Stickstoff im Humuspool: ein 15N markierter Buchenstreuversuch, Annual meeting of the Deutsche Bodenkundliche Gesellschaft 2011 in Berlin, Germany, 03.- 09.09.2011
Bimüller C, Naumann P S, Buegger F, Kögel-Knabner I
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(2012): Gross nitrogen fluxes in intact beech-soil-microbe systems under simulated climate change. Eurosoil 2012 in Bari, Italy, 02.-06.07.2012
Dannenmann M, TejedorJ, Bilela S, Gasche R, Gschwendtner S, Leberecht M, Bimüller C, Kögel-Knabner I, Polle A, Schloter M, Rennenberg H
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(2012): Stabilization of organic N in recalcitrant pools: a 15N litter labeling experiment. Eurosoil 2012 in Bari, Italy, 02. – 06.07.2012
Bimüller C, Naumann P S, Buegger F, Dannenmann M, Zeller B, Gasche R, Papen H, Kögel-Knabner I
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(2013): Gross nitrogen fluxes in intact beech-soil-microbe systems under experimentally simulated climate change. General Assembly 2013 of the European Geosciences Union in Vienna, Austria, 07. – 12.04.2013
Tejedor J, Bilela S, Gasche R, Gschwendtner S, Leberecht M, Bimüller C, Kögel- Knabner I, Polle A, Schloter M, Rennenberg H, Dannenmann M
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(2013): Minor contribution of leaf litter to N nutrition of beech (Fagus sylvatica) seedlings in a mountainous beech forest of Southern Germany. Plant and Soil 369 (1-2): 657–668
Guo C, Simon J, Gasche R, Naumann P S, Bimüller C, Pena R, Polle A, Kögel- Knabner I, Zeller B, Rennenberg H, Dannenmann M
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(2013): Prolonged summer droughts retard soil N processing and stabilization in organo-mineral fractions. Soil Biology and Biochemistry, 68, 241– 251
Bimüller C, Dannenmann M, Tejedor J, von Lützow M, Buegger F, Meier R, Haug S, Schroll R, Kögel-Knabner I
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(2013): Rapid transfer of 15N from labeled beech leaf litter to functional soil organic matter fractions in a Rendzic Leptosol. Soil Biology and Biochemistry, 58, 323–331
Bimüller C, Naumann P, Buegger F, Dannenmann F, Zeller B, von Lützow M, Kögel- Knabner I
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(2013): Welchen Einfluss hat Sommertrockenheit auf die Stickstoffverteilung einer Rendzina? Annual meeting of the Deutsche Bodenkundliche Gesellschaft 2013 in Rostock, Germany, 07. – 12.09.2013
Bimüller C, Dannenmann M, Tejedor J, Gasche R, Buegger F, Schroll R, Bilela S, Rennenberg H, Kögel-Knabner I
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(2014): Climate change impairs processes of N cycling in European beech forests on calcareous soil. General Assembly 2014 of the European Geosciences Union in Vienna, Austria. 27.04. – 02.05.2014
Tejedor J, Bilela S, Gasche R, Gschwendtner S, Leberecht M, Bimüller C, Kögel- Knabner I, Polle A, Schloter M, Rennenberg H, Simon J, Hanewinkel M, Baltensweiler A, Dannenmann M
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Decoupled carbon and nitrogen mineralization in soil particle size fractions of a forest topsoil. Soil Biology and Biochemistry, Volume 78, November 2014, Pages 263-273
Bimüller C, Mueller C W, von Lützow M, Kreyling O, Kölbl A, Haug, S, Schloter M, Kögel-Knabner I
