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Importance of point sources on regional nitrous oxide fluxes in semi-arid steppe of Inner Mongolia, China

机译：点源对内蒙古半干旱草原区域一氧化二氮通量的重要性

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The aim of the present work was to estimate the contribution of different point and diffuse sources to the regional N2O emission strength of steppe in the Xilin river catchment, Inner Mongolia, People's Republic of China. Transect studies showed that the topographic effect on N2O emissions from upland soils was negligible and that upland steppe is only a very weak net source of N2O during the growing season (0.8+or-0.4 micro g N2O-N m-2 h-1). Slightly higher emissions were found for riparian areas (1.8+or-0.3 micro g N2O-N m-2 h-1), which cover ~4% of the landscape. Even faeces or urine additions stimulated N2O emissions from steppe soils only weakly (<2.5 micro g N2O-N m-2 h-1 for a 5 days period). Due to low moisture contents, N2O emissions from dung heaps were also rather low (6.2+or-0.8 micro g N2O-N kg-1 dry matter h-1). In contrast, three orders of magnitude higher N2O emissions were found at sheepfolds (2.45 mg N2O-N m-2 h-1 on average). By calculating N2O emissions on a landscape scale, we show that point sources, and especially sheepfolds, become the dominating regional N2O source during the growing season if stocking rates are >1 sheep ha-1. Our results indicate that the common grazing management in the Xilin river region leads to a translocation of nitrogen from large source areas towards defined spots. This finding is further supported by measurements of NH3 concentrations at different sites. Since most of the nitrogen accumulated in these hot spots is finally lost through burning of the dried excrements by the farmers for heating and cooking purposes, the ecosystem faces a significant human perturbation of regional N cycling, which may contribute to an accelerated degradation of steppe in the Xilin river region..
机译：本工作的目的是估算中华人民共和国内蒙古锡林河流域草原不同点和扩散源对区域N2O排放强度的贡献。断面研究表明，地形对旱地土壤N2O排放的影响可以忽略不计，而旱地草原在生长季节只是N2O的极弱净来源（0.8+或-0.4 micro g N2O-N m-2 h-1）。 。在河岸地区发现的排放量略高（1.8+或-0.3 micro g N2O-N m-2 h-1），其覆盖了约4％的景观。甚至粪便或尿液的添加也仅微弱地刺激了草原土壤的N2O排放（在5天的时间内<2.5 micro g N2O-N m-2 h-1）。由于水分含量低，粪便堆中的N2O排放也很低（6.2+或-0.8 micro g N2O-N kg-1干物质h-1）。相反，在羊圈处发现的N2O排放量增加了三个数量级（平均为2.45 mg N2O-N m-2 h-1）。通过在景观尺度上计算N2O排放量，我们表明，如果放养率> 1绵羊ha-1，点源，尤其是羊圈将成为生长季节中主要的区域N2O源。我们的研究结果表明，锡林河地区常见的放牧管理导致氮从大源区向特定点的转移。测量不同位置的NH3浓度进一步支持了这一发现。由于这些热点中积累的大部分氮最终通过农民燃烧干粪便以供热和烹饪目的而损失掉，因此生态系统面临着人类对区域氮循环的严重干扰，这可能会加速草原中氮的降解。锡林河地区

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