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Importance of heterotrophic nitrification and dissimilatory nitrate reduction to ammonium in a cropland soil: Evidences from a 15N tracing study to literature synthesis

Artikel i vetenskaplig tidskrift
Författare Z Chen
W Ding
Y Xu
Christoph Müller
Tobias Rütting
H Yu
J Fan
J Zhang
T Zhu
Publicerad i Soil Biology and Biochemistry
Volym 91
Sidor 65-75
ISSN 0038-0717
Publiceringsår 2015
Publicerad vid Institutionen för geovetenskaper
Sidor 65-75
Språk en
Länkar dx.doi.org/10.1016/j.soilbio.2015.0...
Ämnesord soil, nitrogen, 15N, review, nitrification, nitrate, biogeochemistry
Ämneskategorier Miljövetenskap, Annan geovetenskap och miljövetenskap, Terrestrisk ekologi, Markvetenskap, Markbiologi

Sammanfattning

Future climate change is predicted to influence soil moisture regime, a key factor regulating soil nitrogen (N) cycling. To elucidate how soil moisture affects gross N transformation in a cultivated black soil, a 15N tracing study was conducted at 30%, 50% and 70% water-filled pore space (WFPS). While gross mineralization rate of recalcitrant organic N (Nrec) increased from 0.56 to 2.47 mg N kg−1 d−1, the rate of labile organic N mineralization declined from 4.23 to 2.41 mg N kg−1 d−1 with a WFPS increase from 30% to 70%. Similar to total mineralization, no distinct moisture effect was found on total immobilization of ammonium, which primarily entered the Nrec pool. Nitrate (NO3−) was mainly produced via autotrophic nitrification, which was significantly stimulated by increasing WFPS. Unexpectedly, heterotrophic nitrification was observed, with the highest rate of 1.06 mg N kg−1 d−1 at 30% WFPS, contributing 31.8% to total NO3− production, and decreased with WFPS. Dissimilatory nitrate reduction to ammonium (DNRA) increased from near zero (30% WFPS) to 0.26 mg N kg−1 d−1 (70% WFPS), amounting to 16.7–92.9% of NO3− consumption. A literature synthetic analysis from global multiple ecosystems showed that the rates of heterotrophic nitrification and DNRA in test soil were comparative to the forest and grassland ecosystems, and that heterotrophic nitrification was positively correlated with precipitation, soil organic carbon (SOC) and C/N, but negatively with pH and bulk density, while DNRA showed positive relationships with precipitation, clay, SOC, C/NO3− and WFPS. We suggested that low pH and bulk density and high SOC and C/N in test soil might favor heterotrophic nitrification, and that C and NO3− availability together with anaerobic condition were crucial for DNRA. Overall, our study highlights the role of moisture in regulating gross N turnover and the importance of heterotrophic nitrification for NO3− production under low moisture and DNRA for NO3− retention under high moisture in cropland.

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