N2O, NO, N2 and CO2 emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores
N2O, NO, N2 and CO2 emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores
复制标题
DOI：
10.5194/bg-11-6047-2014
复制
发表时间：
2014-11
期刊：
影响因子：
4.9
通讯作者：
C. Werner;K. Reiser;M. Dannenmann;L. Hutley;J. Jacobeit;K. Butterbach‐Bahl
中科院分区：
文献类型：
--
作者：
C. Werner;K. Reiser;M. Dannenmann;L. Hutley;J. Jacobeit;K. Butterbach‐Bahl
在澳大利亚北方，土壤湿度和温度的季节性变化很大，这是一个明显的环境特征。然而，这种变化如何影响土壤-大气交换的一氧化二氮（N2 O），一氧化氮（NO）和二氮（N2）仍然没有得到很好的探讨。通过培养来自四个地点（三个稀树草原，一个牧场）的完整土芯，在控制土壤温度（ST）和土壤湿度（SM）的条件下，研究了N2 O、NO和CO2的释放。此外，由于反硝化作用的N2释放的氦气流土芯技术进行了测量。在干燥的预培养条件下，NO和N2 O排放量非常低（−2 h −1 ; 2 O-N m −2 h −1），或者在N2 O的情况下，甚至观察到净土壤吸收。实质性NO（最大值：306.5 μg N m −2 h −1）和相对较小的N2 O脉冲排放（最大值：5.8 ± 5.0 μg N m −2 h −1），但这些脉冲持续时间较短，最多只能持续3天。氮素的大气损失主要是N2排放（占总损失的82.4-99.3%），而在50%SM和30 °C ST培养条件下，NO排放占总损失的43.2%（在这些土壤条件下N2的贡献仅为53.2%）。12个样点中有3个样点的N2 O排放量系统性较高，这表明在样点水平上存在很大的空间变异性，但平均而言，土壤充当弱N2 O源甚至汇。通过使用保守的高档方法，我们估计热带稀树草原土壤的年排放总量平均为0.12 kg N ha −1 yr −1（N2 O）、0.68 kg N ha −1 yr −1（NO）和6.65 kg N ha −1 yr −1（N2）。长期SM和ST记录的分析表明，极端土壤饱和，可导致高N2 O和N2排放量每年只发生几天，因此对全年的影响很小。与年排放总量相比，脉冲事件释放的氮的潜在贡献被发现对NO排放具有重要意义（占总量的5-22%），但对N2 O排放不具有重要意义。我们的研究结果表明，从这些土壤中释放的氮的总气体是低的，显然占主导地位的惰性氮的形式损失。季节性变化的土壤温度和湿度的影响进行了检测，但被认为是低的，由于土壤中的有效氮量少（总氮<0.1%）。
Strong seasonal variability of hygric and thermal soil conditions are a defining environmental feature in northern Australia. However, how such changes affect the soil–atmosphere exchange of nitrous oxide (N 2 O), nitric oxide (NO) and dinitrogen (N 2 ) is still not well explored. By incubating intact soil cores from four sites (three savanna, one pasture) under controlled soil temperatures (ST) and soil moisture (SM) we investigated the release of the trace gas fluxes of N 2 O, NO and carbon dioxide (CO 2 ). Furthermore, the release of N 2 due to denitrification was measured using the helium gas flow soil core technique. Under dry pre-incubation conditions NO and N 2 O emissions were very low ( −2 h −1 ; 2 O-N m −2 h −1 ) or in the case of N 2 O, even a net soil uptake was observed. Substantial NO (max: 306.5 μg N m −2 h −1 ) and relatively small N 2 O pulse emissions (max: 5.8 ± 5.0 μg N m −2 h −1 ) were recorded following soil wetting, but these pulses were short lived, lasting only up to 3 days. The total atmospheric loss of nitrogen was generally dominated by N 2 emissions (82.4–99.3% of total N lost), although NO emissions contributed almost 43.2% to the total atmospheric nitrogen loss at 50% SM and 30 °C ST incubation settings (the contribution of N 2 at these soil conditions was only 53.2%). N 2 O emissions were systematically higher for 3 of 12 sample locations, which indicates substantial spatial variability at site level, but on average soils acted as weak N 2 O sources or even sinks. By using a conservative upscale approach we estimate total annual emissions from savanna soils to average 0.12 kg N ha −1 yr −1 (N 2 O), 0.68 kg N ha −1 yr −1 (NO) and 6.65 kg N ha −1 yr −1 (N 2 ). The analysis of long-term SM and ST records makes it clear that extreme soil saturation that can lead to high N 2 O and N 2 emissions only occurs a few days per year and thus has little impact on the annual total. The potential contribution of nitrogen released due to pulse events compared to the total annual emissions was found to be of importance for NO emissions (contribution to total: 5–22%), but not for N 2 O emissions. Our results indicate that the total gaseous release of nitrogen from these soils is low and clearly dominated by loss in the form of inert nitrogen. Effects of seasonally varying soil temperature and moisture were detected, but were found to be low due to the small amounts of available nitrogen in the soils (total nitrogen <0.1%).