Soil organic N cycling – MicrON

Nitrogen (N) availability in soils exerts a strong control on the terrestrial carbon (C) cycle, through effects on plant production and on microbial processes, such as organic matter decomposition and soil microbial respiration. The predicted global changes in temperature and precipitation, rising levels of atmospheric carbon dioxide and increasing N deposition call for a better understanding of the soil N cycle and its underlying processes in order to accurately predict future responses of the Earths C and N cycles to environmental changes.

Although the importance of N availability for soil C sequestration is well established, we know surprisingly little about the actual bottleneck in the soil N cycle, i.e.

(1) the decomposition of soil organic N, and

(2) about the microbial nitrogen-use efficiency (NUE).

Microbial NUE represents the fraction of organic N taken up that is invested into microbial biomass growth, while the excess of organic N is mineralized and recycled to the environment in the form of ammonium. During this mineralization step organic C is released that can be used for energy production (respiration) or biomass production. Microbial NUE therefore is a key biogeochemical parameter determining the fraction of organic matter breakdown products incorporated into microbial biomass and therefore sequestered in soil, as microbial residues comprise a large fraction of stable soil organic matter, and as it causes an intermittent decoupling of the soil N and C cycles. We therefore seek to advance our mechanistic understanding of organic N metabolism of soil and litter microbial communities that drive soil N sequestration and soil organic N dynamics. We investigate edaphic, climatic and land management controls of soil organic N cycling processes and of microbial NUE in different types of soil across a continental gradient in Europe in natural and managed ecosystems. Microcosm experiments help understanding the short-term responses of organic nitrogen decomposition and microbial NUE to environmental changes or resource manipulations, and allow the calibration of a biogeochemical model by model-data fusion approaches.

Publications:

M. Mooshammer, W. Wanek, I. Hämmerle, L. Fuchslueger, F. Hofhansl, A. Knoltsch, J. Schnecker, M. Takriti, M. Watzka, B. Wild, K. M. Keiblinger, S. Zechmeister-Boltenstern, A. Richter (2014) Adjustment of microbial nitrogen use efficiency to carbon:nitrogen imbalances regulates soil N cycling. Nature Communications 5: article no 3694.
B. Wild, J. Schnecker, A. Knoltsch, M. Takriti, M. Mooshammer, N. Gentsch, R. Mikutta, R.J. Alves, A. Gittel, N. Lashchinskiy, A. Richter (2015) Microbial nitrogen dynamics in organic and mineral soil horizons along a latitudinal transect in western Siberia. Global Biogeochemical Cycles 29, 567-582.
J. Prommer, W. Wanek, F. Hofhansl, D. Trojan, P. Offre, T. Urich, C. Schleper, S. Sassmann, B. Kitzler, G. Soja, RC. Hood-Nowotny (2014) Biochar decelerates soil organic nitrogen cycling but stimulates soil nitrification in a temperate arable field trial. PLOS ONE 9: e86388. E.
Inselsbacher, W. Wanek, J. Strauss, S. Zechmeister-Boltenstern, C. Müller (2013) A novel 15N tracer model reveals: Plant nitrate uptake governs nitrogen transformation rates in agricultural soils. Soil Biology and Biochemistry 57, 301-310.
M. Mooshammer, W. Wanek, J. Schnecker, B. Wild, S. Leitner, F. Hofhansl, A. Blöchl, I. Hämmerle, A.H. Frank, L. Fuchslueger, K.M. Keiblinger, S. Zechmeister-Boltenstern, A. Richter (2012) Stoichiometric controls of nitrogen and phosphorus cycling in decomposing beech leaf litter. Ecology 93(4), 770-782.
W. Wanek, M. Mooshammer, A. Blöchl, A. Hanreich, A. Richter (2010) Determination of gross rates of amino acid production and immobilization in decomposing leaf litter by a novel isotope pool dilution technique. Soil Biology and Biochemistry 42, 1293-1302.

Investigated by:

Wolfgang Wanek

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