An assessment of N-cycling and sources of N2O during a simulated rain event using natural abundance 15N
An assessment of N-cycling and sources of N2O during a simulated rain event using natural abundance 15N
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DOI：
10.1016/j.agee.2012.11.012
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发表时间：
2013-01-15
影响因子：
6.6
通讯作者：
Six, Johan
中科院分区：
文献类型：
--
作者：
Decock, Charlotte;Six, Johan
为了准确预测农业土壤N2O排放并制定有效的管理策略，了解田间条件下N2O排放的机制非常重要。这涉及到确定N2O的来源，目前在方法上具有挑战性，特别是在野外条件下。通过对加州中央谷地一年生种植系统的降雨模拟，评估了N-15示踪剂和N-15天然丰度对研究N循环和N2O来源的适用性。我们的自然丰度N-15方法与其他研究的不同之处，在于强调对N2O排放的每事件（例如本研究中的降雨模拟）评估，在该事件期间采用高时间采样频率，测定NH4+和NO3-除N2O外的N-15，以及使用同位素模型进行数据分析。在我们的研究中，N-15示踪剂评估N循环和N2O排放源的适用性受到限制，可能是由于土壤质地较细，使用未受干扰的土芯，以及N-15施用量低。基于自然丰度N-15，分别计算出5.37 +/- 1.72、2.70 +/- 1.72、3.01 +/- 1.13和0.15 +/- 0.29 μ g N g（-1）土壤d（-1）下总NH4+矿化率、NH4+固定化率、硝化率和NO3-固定化率。然而，自然丰度N-15不能很好地预测硝化与反硝化对N2O产量的贡献。然而，可以观察到N2O减少率的重要趋势，在降雨模拟后2 - 24小时内，产生的N2O减少量从48%急剧增加到78%，然后在降雨模拟后第5天逐渐下降到46%。我们的结论是，自然丰度N-15方法非常有希望阐明在农业管理或天气事件中驱动n循环和N2O排放的机制，特别是如果同位素动力学被纳入特定地点的生物地球化学过程模型。(C) 2012 Elsevier B.V.版权所有
In order to accurately predict N2O emissions from agricultural soils and to develop effective management strategies, it is important to understand mechanisms underlying N2O emissions under field conditions. This involves identification of sources of N2O, which is currently methodologically challenging, especially under field conditions. We assessed the suitability of N-15 tracers and natural abundance N-15 to study N cycling and sources of N2O after a rainfall simulation in an annual cropping system in the Central Valley of California. Our natural abundance N-15 approach differed from other studies due to a combination of emphasizing a per-event (e.g. rainfall simulation in this study) assessment of N2O emissions, applying high temporal sampling frequency during this event, determination of N-15 of NH4+ and NO3- in addition to N2O, and data analysis using isotope models. In our study, the suitability of N-15 tracers to assess N cycling and sources of N2O emissions was limited, likely due to a combination of a fine soil texture, the use of undisturbed soil cores, and a low N-15 application rate. Based on natural abundance N-15, we were able to calculate gross NH4+ mineralization, NH4+ immobilization, nitrification and NO3- immobilization rates of 5.37 +/- 1.72, 2.70 +/- 1.72, 3.01 +/- 1.13 and 0.15 +/- 0.29 mu g N g(-1) soil d(-1), respectively. Natural abundance N-15 was, however, a rather poor predictor of the contribution of nitrification versus denitrification to N2O production. Nevertheless, important trends in N2O reduction rates could be observed, showing a sharp increase from 48% to 78% in reduction of produced N2O between 2 hours and 24 hours after rainfall simulation, followed by a gradual decrease to 46% of reduction by the fifth day after rainfall simulation. We conclude that the natural abundance N-15 approach is very promising to elucidate mechanisms driving N-cycling and N2O emissions during agricultural management or weather events, especially if isotope dynamics are incorporated in site-specific biogeochemical process models. (C) 2012 Elsevier B.V. All rights reserved.