Importance of point sources on regional nitrous oxide fluxes in semi-arid steppe of Inner Mongolia, China
Importance of point sources on regional nitrous oxide fluxes in semi-arid steppe of Inner Mongolia, China
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DOI：
10.1007/s11104-007-9311-8
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发表时间：
2007-06
期刊：
影响因子：
4.9
通讯作者：
J. Holst;C. Liu;Z. Yao;N. Brüggemann;X. Zheng;X. Han;K. Butterbach‐Bahl
中科院分区：
文献类型：
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作者：
J. Holst;C. Liu;Z. Yao;N. Brüggemann;X. Zheng;X. Han;K. Butterbach‐Bahl
本研究的目的是估算不同点源和扩散源对内蒙古锡林河流域草原N2O排放强度的贡献。样带研究表明，地形对旱地土壤N2O排放的影响可以忽略不计，旱地草原在生长季节只是一个非常弱的N2O净来源(0.8g N2O-N/mμ−2h−1)。河岸地区的排放量略高(1.8gμg N2O-N−2h−1)，占∼景观的4%。即使粪便或尿液的添加也只能微弱地刺激草原土壤中N2O的排放(<；2.5gμg N2O-N−2.5h−1，为期5天)。由于水分含量较低，粪便中N2O的排放量也很低(6.2%±0.8%μg N2O-N/kg−1干物质/h−1)。相比之下，羊圈的N2O排放量高出三个数量级(平均2.45亿mg N2O-N/m−2h−1)。通过在景观尺度上计算N2O排放量，我们发现，如果放牧率为>；1/ha−1，则点源，尤其是羊圈成为生长季区域N2O的主要来源。我们的结果表明，锡林河流域普遍的放牧管理导致了氮素从大源区向限定点位的转移。对不同地点NH3浓度的测量进一步支持了这一发现。由于这些热点地区积累的大部分氮最终通过农民焚烧干粪便来取暖和烹饪而损失，生态系统面临着区域N循环的显著人类扰动，这可能导致锡林河地区草原加速退化。
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 ± 0.4 μg N2O–N m−2h−1). Slightly higher emissions were found for riparian areas (1.8 ± 0.3 μg N2O–N m−2h−1), which cover ∼4% of the landscape. Even faeces or urine additions stimulated N2O emissions from steppe soils only weakly (<2.5 μg N2O–N m−2h−1for a 5 days period). Due to low moisture contents, N2O emissions from dung heaps were also rather low (6.2 ± 0.8 μg N2O–N kg−1dry matter h−1). In contrast, three orders of magnitude higher N2O emissions were found at sheepfolds (2.45 mg N2O–N m−2h−1on 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 NH3concentrations 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.