土壤饱和度对草地土壤反硝化作用的影响,Biogeosciences

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土壤饱和度对草地土壤反硝化作用的影响
Biogeosciences ( IF 3.9 ) Pub Date : 2017-10-23 , DOI: 10.5194/bg-14-4691-2017
Laura Maritza Cardenas , Roland Bol , Dominika Lewicka-Szczebak , Andrew Stuart Gregory , Graham Peter Matthews , William Richard Whalley , Thomas Henry Misselbrook , David Scholefield , Reinhard Well

一氧化二氮（N ₂ O）作为温室气体和平流层中臭氧（O ₃）破坏的前体（主要在土壤中产生）至关重要。土壤排放的N ₂ O通常主要来自反硝化作用，而在较小程度上则来自硝化作用，这两个过程均受环境因素及其相互作用的影响，并受到农业经营的影响。以含水孔隙空间（WFPS）表示的土壤含水量是排放的主要控制因素，并且其与压实的相互作用尚未在微孔尺度上进行研究。在不同饱和度下对草地土壤以及N ₂ O和N _2的排放进行了实验室培养测定了N ₂ O的同位素，并测量了N ₂ O的同位素。我们发现，在饱和度较低的土壤中通量变化较大，这可能是由于土壤裂缝和养分热点造成的养分分布异质性所致。结果与反硝化相一致，是最高饱和度时通量的主要来源，但即使湿度仍然很高（WFSP为71％），也可能在较低饱和度时发生硝化作用。同位素数据表明，在最湿润的处理方法中，与两种干燥方法相比，同位素相似。结果与以前的发现一致，很明显，有两个N池具有不同的动力学特征：添加的N产生强烈的反硝化作用，而土壤N导致的同位素分馏较少。

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Effect of soil saturation on denitrification in a grassland soil

Nitrous oxide (N₂O) is of major importance as a greenhouse gas and precursor of ozone (O₃) destruction in the stratosphere mostly produced in soils. The soil-emitted N₂O is generally predominantly derived from denitrification and, to a smaller extent, nitrification, both processes controlled by environmental factors and their interactions, and are influenced by agricultural management. Soil water content expressed as water-filled pore space (WFPS) is a major controlling factor of emissions and its interaction with compaction, has not been studied at the micropore scale. A laboratory incubation was carried out at different saturation levels for a grassland soil and emissions of N₂O and N₂ were measured as well as the isotopocules of N₂O. We found that flux variability was larger in the less saturated soils probably due to nutrient distribution heterogeneity created from soil cracks and consequently nutrient hot spots. The results agreed with denitrification as the main source of fluxes at the highest saturations, but nitrification could have occurred at the lower saturation, even though moisture was still high (71 % WFSP). The isotopocules data indicated isotopic similarities in the wettest treatments vs. the two drier ones. The results agreed with previous findings where it is clear there are two N pools with different dynamics: added N producing intense denitrification vs. soil N resulting in less isotopic fractionation.

更新日期：2017-10-23

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