Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8363757 | Soil Biology and Biochemistry | 2015 | 11 Pages |
Abstract
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 kgâ1 dâ1, the rate of labile organic N mineralization declined from 4.23 to 2.41 mg N kgâ1 dâ1 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 (NO3â) 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 kgâ1 dâ1 at 30% WFPS, contributing 31.8% to total NO3â production, and decreased with WFPS. Dissimilatory nitrate reduction to ammonium (DNRA) increased from near zero (30% WFPS) to 0.26 mg N kgâ1 dâ1 (70% WFPS), amounting to 16.7-92.9% of NO3â 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/NO3â 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 NO3â 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 NO3â production under low moisture and DNRA for NO3â retention under high moisture in cropland.
Keywords
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Soil Science
Authors
Zengming Chen, Weixin Ding, Yehong Xu, Christoph Müller, Tobias Rütting, Hongyan Yu, Jianling Fan, Jinbo Zhang, Tongbin Zhu,