N2O and NO fluxes between a Norway spruce forest soil and atmosphere as affected by prolonged summer drought
N2O and NO fluxes between a Norway spruce forest soil and atmosphere as affected by prolonged summer drought
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DOI：
10.1016/j.soilbio.2009.07.001
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发表时间：
2009-09
影响因子：
9.7
通讯作者：
S. Goldberg;G. Gebauer
中科院分区：
文献类型：
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作者：
S. Goldberg;G. Gebauer
全球变化预测中欧夏季干旱的频率和持续时间会增加，特别是在高海拔地区。我们目前对土壤干旱对温带森林土壤氮痕量气体通量的影响的了解还很少。在这项研究中，连续两年在德国巴伐利亚州东北部菲赫特尔格伯里的一片成熟的挪威云杉林中，研究了人工干旱对土壤N2O和NO排放的影响。干旱是由为期46天的屋顶施工引起的。实验分三个重复进行，三个非操纵区作为对照。除了每周至每月一次的N2O和NO通量测量外，还对6个不同土壤深度的土壤气体样本进行了N2O浓度和同位素丰度的时间序列分析，以研究土壤中N2O的动态变化。在干旱期间，试验地从土壤到大气的N2O通量在干旱期间逐渐减少，分别为0.2g/−~0.0g/μ·m~(-1)·−~(-2)·−~(-1)，与2007年对照相比，试验区的平均累积N2O排放量减少了43%。土壤剖面上的N2O浓度和同位素丰度分析表明，即使在干旱期间，土壤的大部分也是N2O的净汇。这种N2O汇，加上有机层中N2O产生的减少，导致干旱期间N2O通量的连续下降，甚至可能像在实验第一年观察到的那样，将这种森林土壤变成大气N2O的净汇。再湿至0.1molμ−2 h−1后，N2O通量增加，但不能补偿之前的干旱影响。在2006年的试验中，在20 cm土层土壤基质势至−630 hpa的情况下，穿透雨排除小区的累积NO排放量比对照减少了69%，而2007年土壤基质势最小为−210 hpa的试验区的累积NO排放量是对照的180%。湿润后，穿透雨排除区土壤的NO通量显著大于对照(高达9μ−/m−2 h−1对2μmol/m−2 h−1)。在整个实验过程中，这些通量占NO排放总量的44%。除冬季外，这种森林土壤的NO排放量通常比N2O排放量高一个数量级或更多。
Global change scenarios predict an increasing frequency and duration of summer drought periods in Central Europe especially for higher elevation areas. Our current knowledge about the effects of soil drought on nitrogen trace gas fluxes from temperate forest soils is scarce. In this study, the effects of experimentally induced drought on soil N2O and NO emissions were investigated in a mature Norway spruce forest in the Fichtelgebirge (northeastern Bavaria, Germany) in two consecutive years. Drought was induced by roof constructions over a period of 46 days. The experiment was run in three replicates and three non-manipulated plots served as controls. Additionally to the N2O and NO flux measurements in weekly to monthly intervals, soil gas samples from six different soil depths were analysed in time series for N2O concentration as well as isotope abundances to investigate N2O dynamics within the soil. N2O fluxes from soil to the atmosphere at the experimental plots decreased gradually during the drought period from 0.2 to −0.0 μmol m−2h−1, respectively, and mean cumulative N2O emissions from the manipulated plots were reduced by 43% during experimental drought compared to the controls in 2007. N2O concentration as well as isotope abundance analysis along the soil profiles revealed that a major part of the soil acted as a net sink for N2O, even during drought. This N2O sink, together with diminished N2O production in the organic layers, resulted in successively decreased N2O fluxes during drought, and may even turn this forest soil into a net sink of atmospheric N2O as observed in the first year of the experiment. Enhanced N2O fluxes observed after rewetting up to 0.1 μmol m−2h−1were not able to compensate for the preceding drought effect. During the experiment in 2006, with soil matric potentials in 20 cm depth down to −630 hPa, cumulative NO emissions from the throughfall exclusion plots were reduced by 69% compared to the controls, whereas cumulative NO emissions from the experimental plots in 2007, with minimum soil matric potentials of −210 hPa, were 180% of those of the controls. Following wetting, the soil of the throughfall exclusion plots showed significantly larger NO fluxes compared to the controls (up to 9 μmol m−2h−1versus 2 μmol m−2h−1). These fluxes were responsible for 44% of the total emission of NO throughout the whole course of the experiment. NO emissions from this forest soil usually exceeded N2O emissions by one order of magnitude or more except during wintertime.