不同土地利用方式对黑土团聚体内有机碳红外光谱特征的影响
Effects of land use patterns on the characteristics of Fourier Infrared Spectroscopy of organic carbon within aggregates in a Mollisols
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摘要: 土壤团聚体为有机碳提供物理保护，是土壤碳固存和稳定的主要场所。团聚体内有机碳的数量和化学结构对评价有机碳的稳定性至关重要。以1985年建立在黑龙江海伦农田生态系统国家野外科学观测研究站内的不同土地利用方式长期定位试验(农田、草地、林地和裸地)为研究对象，采用团聚体分级和傅里叶红外光谱技术，研究了长期不同利用方式对黑土团聚体内有机碳的分布和化学光谱结构特征的影响。结果发现，与对照农田相比，经过35年不同土地利用方式后，土壤总有机碳和全氮含量、团聚体稳定性及团聚体内有机碳的化学官能团相对峰面积发生不同程度变化。草地和林地处理提高了土壤有机碳含量和碳活性官能团的相对峰面积，草地处理>0.25 mm粒径团聚体质量分数最大，团聚体稳定性最高。裸地与农田相似，土壤碳氮含量和有机碳活性官能团相对峰面积较低，土壤团聚体以 < 0.25 mm粒径为主，团聚体稳定性也较低。进一步比较了干筛和湿筛两种筛分方法得到的土壤团聚体的力稳性与水稳性，发现与农田相比，草地显著提升了土壤团聚体的力稳性和水稳性，林地团聚体的力稳性显著降低，裸地团聚体的水稳性显著降低。相关性和主成分分析表明，草地和林地处理主要为1 420 cm-1和2 920 cm-1的活性碳组分官能团，而农田和裸地处理主要为1 630 cm-1稳定性的芳香族官能团。退耕还林还草是提升黑土团聚体固碳能力的有效措施，其通过增强土壤团聚体的稳定性改善土壤结构，提高土壤团聚体内有机碳的数量和稳定性化学官能团的相对比例，增加土壤的固碳能力。大团聚体内碳的活性官能团相对峰面积对不同土地利用方式的响应更敏感，对提高土壤有机碳含量的贡献更大，可作为反映土壤有机碳变化的敏感指标。Abstract:
Soil aggregates provide physical protection for soil organic carbon (SOC), and are the main sites for SOC sequestration.The carbon content and its chemical components in soil aggregates are vital important for evaluating the capacity of carbon stabilization.Based on a long-term field experiment with different land use patterns (Cropland, Grassland, Forestland and Bareland) established in the National Observation Station of Hailun Agro-ecology System in 1985, the study investigated the effects of long-term different land use patterns on soil aggregates stability and organic carbon characters within aggregates fractionated by wet sieving and dry sieving methods.The chemical components of organic carbon within aggregates and bulk soil were measured by Fourier Infrared Spectroscopy methods.After 35 years of different land use patterns, the contents of SOC and total nitrogen (TN), aggregate stability and chemical components within aggregates changed significantly, with the largest changes being observed in grassland soil.Compared with the cropland soil, the contents of SOC and TN, and relative peak area of aliphatic-C increased in grassland and forestland.The proportion of >0.25 mm aggregate and mean weight diameter were the highest in grassland.Compared to grassland and forestland, the contents of SOC and TN, and relative peak area of aliphatic-C were lower in bareland and cropland, < 0.25 mm aggregates dominating there, with a lower mean weight diameter and carbon sequestration capacity.The physical stability and water stability of soil aggregates under dry sieving and wet sieving methods were further compared, respectively.Grassland improved the physical stability and water stability of soil aggregates significantly.The physical stability of forestland aggregates decreased significantly, while the water stability of bareland aggregates decreased significantly.Correlation analysis and principal component analysis demonstrated that the aliphatic-C groups in 1 420 cm-1 and 2 920 cm-1 were dominated in grassland and forestland soils, while the aromatic-C group in 1 630 cm-1 was dominated in bareland and cropland soils.The results showed that converting cropland to forestland or grassland is an effective measure to improve the carbon sequestration capacity of soil aggregates, which can increase soil structure stability by enhancing the stability of soil aggregates, improve the quantity of and stable functional groups of OC within aggregates, and finally enhance the carbon sequestration capacity of soil.The proportions of aliphatic-C groups in soil macroaggregates, are more sensitive to changes of land use patterns, would be considered as a sensitive indicator to SOC changes.
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