不同退化程度与人工恢复方式对草原土壤胡敏酸结构的影响

该研究主要探讨不同退化程度和人工恢复方式对草原土壤胡敏酸结构的变化特征,为退化草原恢复提供理论依据.在鄂尔多斯沙地不同退化样地与人工恢复草地,对草原土壤的腐殖酸进行了分离提取,采用元素分析、13核磁共振(NMR)等方法对荒漠草原土壤退化与恢复过程中土壤胡敏酸(HA)不同官能团的含量变化进行分析,并用因子分析法研究它们的结构特征和差异.结果表明:不同退化及恢复阶段HA碳骨架相似,但各类碳原子(官能团)的含量不同,芳香族和脂肪族结构在胡敏酸结构中发挥了重要作用.退化阶段,土壤HA的芳香碳减少,碳水化合物减少,土壤HA的氧化程度增加,疏水程度降低.恢复阶段土壤芳香碳含量增加,碳水化合物含量增加,疏水程度略有降低.土壤退化及恢复阶段,胡敏酸(HA)的结构变化最大的部分是芳香碳、取代脂肪碳结构,其次是羧基和酯基碳和未取代脂肪碳结构.植被恢复对腐殖酸结构的变化有重要的影响,本氏针茅区和本氏针茅+油蒿区的HA结构中芳香化程度和复合程度较高,氧化程度低.围栏样区内土壤胡敏酸(H A)的酸度相对较高,芳香化程度和复合程度仍然较低.因此,土壤胡敏酸结构特征的变化可以反映草原土壤的退化程度,进一步揭示草原土壤退化的机制.

Structural Changes in Humic Acid during Degeneration Process of a Steppe Soil

Degradation of grassland causes changes in internal properties of soil,such as the structure and characteristic of humic acid.Humic acids were extracted from a steppe soil under different degeneration sta-ges.Elemental analysis and 13 C nuclear magnetic resonance spectroscopy were used to study the structural changes of soil humic acid in the steppe soil.Structural changes in HA was investigated with Factor Analysis. The results showed that the basic carbon frameworks of HA were similar under different degeneration stages. During the process of degeneration,the content of aromatic carbon,and carbohydrates in soil HA decreased. In addition,the oxidation of HA was increased while the hydrophobicity was declining.During the recovery process,the content of aromatic carbon,and carbohydrates in soil HA increased while the hydrophobicity was declined.The aromaticity and polymerization of HA in S.bungeana area,S.bungeana+A.Sphaerocephala area was higher with lower oxidation;the acidity of HA in fenced area was higher,but the aromaticity and pol-ymerization were lower.The results verified that vegetation recovery imposed an important effect on humic acid structure;besides,aromatic groups and aliphatic groups played an important role in the formation of sta-ble humic acid structure.