Rapid nitrate reduction produces pulsed NO and N2O emissions following wetting of dryland soils
Rapid nitrate reduction produces pulsed NO and N2O emissions following wetting of dryland soils
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DOI：
10.1007/s10533-022-00896-x
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发表时间：
2022-02
期刊：
影响因子：
4
通讯作者：
Alexander H. Krichels;Peter M. Homyak;E. Aronson;J. Sickman;Jon K. Botthoff;Hannah B Shulman;S. Piper;Holly M. Andrews;G. D. Jenerette
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作者：
Alexander H. Krichels;Peter M. Homyak;E. Aronson;J. Sickman;Jon K. Botthoff;Hannah B Shulman;S. Piper;Holly M. Andrews;G. D. Jenerette
土壤干燥和湿润周期会产生一氧化氮（NO）和一氧化二氮（N2 O）排放脉冲，对区域空气质量和地球气候产生重大影响。虽然脉冲产生的N排放在整个生态系统中是普遍存在的，但脉冲幅度和时间的控制过程仍不清楚。我们研究了在两个对比鲜明的旱地，沙漠和查帕拉尔，尽管炎热和干燥的条件下已知的限制生物过程中，一些最高的NO和N2 O通量率已被测量的脉冲NO和N2 O排放的过程。我们测量N2 O和NO排放量，每30分钟为24小时后，用富含同位素的硝酸盐和铵溶液湿润土壤，以确定生产途径和它们的时间。硝酸盐在湿润后15分钟内被还原为N2 O，排放量超过1000 ng N-N2 O m−2s− 1，并在4小时内恢复到背景水平，但脉冲幅度并没有与添加的铵或硝酸盐的量成比例增加。与N2 O相反，NO的排放超过24小时，并与铵的添加成比例增加，在沙漠和查帕拉尔土壤中超过600 ng N-NO m−2s− 1。同位素示踪剂表明，氨氧化和硝酸盐还原产生NO。两者合计，我们的测量表明，硝酸盐可以在几分钟内减少湿润的夏季干燥的沙漠土壤，产生大的N2 O排放脉冲和多个过程有助于持久的NO排放。这些机制代表了生态系统氮损失的重要途径，也有助于区域空气质量和全球气候动态。
Soil drying and wetting cycles can produce pulses of nitric oxide (NO) and nitrous oxide (N2O) emissions with substantial effects on both regional air quality and Earth’s climate. While pulsed production of N emissions is ubiquitous across ecosystems, the processes governing pulse magnitude and timing remain unclear. We studied the processes producing pulsed NO and N2O emissions at two contrasting drylands, desert and chaparral, where despite the hot and dry conditions known to limit biological processes, some of the highest NO and N2O flux rates have been measured. We measured N2O and NO emissions every 30 min for 24 h after wetting soils with isotopically-enriched nitrate and ammonium solutions to determine production pathways and their timing. Nitrate was reduced to N2O within 15 min of wetting, with emissions exceeding 1000 ng N–N2O m−2s−1and returning to background levels within four hours, but the pulse magnitude did not increase in proportion to the amount of ammonium or nitrate added. In contrast to N2O, NO was emitted over 24 h and increased in proportion to ammonium addition, exceeding 600 ng N–NO m−2s−1in desert and chaparral soils. Isotope tracers suggest that both ammonia oxidation and nitrate reduction produced NO. Taken together, our measurements demonstrate that nitrate can be reduced within minutes of wetting summer-dry desert soils to produce large N2O emission pulses and that multiple processes contribute to long-lasting NO emissions. These mechanisms represent substantial pathways of ecosystem N loss that also contribute to regional air quality and global climate dynamics.