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Title (Primary) Incorporation of N from burnt and unburnt 15N grass residues into the peptidic fraction of fire affected and unaffected soils
Author López-Martín, M.; Nowak, K.M.; Miltner, A.; Knicker, H.;
Journal Journal of Soils and Sediments
Year 2017
Department UBT;
Volume 17
Language englisch;
POF III (all) T41;
Keywords Amino acids; Black nitrogen; Incubation experiment; Isotope ratio mass spectrometry; N turnover in post-fire soils; Pyrogenic organic matter
UFZ wide themes RU3;
Abstract Purpose

To reveal if the input of pyrogenic organic matter (PyOM) affects the nitrogen (N) cycling in soil and its N can be used for the synthesis of microbial biomass, we investigated the incorporation of 15N from 15N-enriched grass residues (OM) or their PyOM into extractable amino acids (AAs) of soil organic matter (SOM) from an unburnt and a burnt soil amended with those residues.

Materials and methods

Pots seeded with Lolium perenne and filled with soil from a burnt and an unburnt Cambisol from southern Spain were topped either with 15N-enriched grass residues (15N-OM), its 15N-PyOM, mixtures of KNO3 (Ni) and 15N-OM or 15N-PyOM, as well as K15NO3 mixed with non-enriched OM or PyOM. After incubation of the pots for up to 16 months under controlled conditions, the AAs, extracted from the litter-free soil, were quantified by gas chromatography mass spectrometry (GC/MS). The fate of the added 15N (15Nadd) was followed by isotopic ratio mass spectrometry (IRMS) and analyzed by statistical means.

Results and discussion

The contribution of extractable AAs to SOM of the non-amended burnt soil was twice of that for the unburnt soil. After amendment, their yields and the percentage of 15Nadd recovered in AAs were always higher for the burnt soil. Stabilization of proteinaceous residues during the incubation was indicated. Already after 2 weeks, 15Nadd from 15N-PyOM was recovered within the AAs.

Conclusions

Our experiment confirmed that N from PyOM is incorporated into the peptidic fraction of SOM of post-fire soils. The efficiency of this incorporation is not altered by the presence of Ni and vice versa. We demonstrated further a short-term and medium-term impact of fire on N cycling in soils, expressed by alteration of the contribution of acid-extractable AAs to the soil organic N (SON) pool.

ID 18864
Persistent UFZ Identifier https://www.ufz.de/index.php?en=20939&ufzPublicationIdentifier=18864
López-Martín, M., Nowak, K.M., Miltner, A., Knicker, H. (2017):
Incorporation of N from burnt and unburnt 15N grass residues into the peptidic fraction of fire affected and unaffected soils
J. Soils Sediments 17 , 1554 - 1564