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应用同步辐射红外光谱技术,分析了宁南山区不同种植年限苜蓿地的不同粒径团聚体中土壤有机碳(soil organic carbon,SOC)官能团的变化.结果表明:种植苜蓿改变了SOC官能团的含量及其在团聚体中的分布.随着种植年限增加,SOC和大团聚体(>0.25mm)含量增加,土壤团聚体的稳定性增强;饱和烷烃相对含量提高,且主要分布在0.25～1mm团聚体中;脂肪-C、醇-C相对含量随着粒径增大而减少,增加的脂肪-C、醇-C主要分布在大团聚体中,芳香-C主要分布于<0.25mm微团聚体中.大团聚体中各官能团相对含量变化幅度大于微团聚体,微团聚体中有机碳稳定性高于大团聚体.连续种植苜蓿使SOC中易氧化官能团(脂肪-C、醇-C)的增幅大于芳香-C,土壤有机碳化学稳定性提高,以苜蓿生长8年时的效果最好.SOC中的脂肪-C、醇-C、饱和烷烃比例较高,且最为活跃,对土壤有机碳增加的贡献明显.
The changes of functional groups of soil organic carbon (SOC) in alfalfa aggregates with different planting years in mountainous areas of southern Ningxia were analyzed by using synchrotron radiation infrared spectroscopy. The results showed that alfalfa alters the content of SOC functional groups, The distribution of SOC and macroaggregates (> 0.25mm) increased, the stability of soil aggregates increased, the relative content of saturated alkanes increased, and mainly distributed in 0.25 ~ 1mm aggregates . The relative content of C and C decreased with the increase of particle size. The increased C and C concentrations were mainly distributed in large aggregates. Aromatic C mainly distributed in <0.25mm microaggregates .The relative content of functional groups in macroaggregates changed more than that of microaggregates and the stability of organic carbon in microaggregates was higher than that of macroaggregates.The growth of easily oxidizable functional groups (aliphatic-C, alcohol-C) Is higher than that of aromatic-C, the chemical stability of soil organic carbon is improved, and alfalfa has the best effect when it grows for 8 years.The proportion of aliphatic-C, alcohol-C and saturated alkane in SOC is higher and the most active, and increases the content of soil organic carbon The contribution is obvious.