开垦对黑土有机质化学结构的影响

Effect of reclamation on the chemical structure of organic matter in black soil

基于傅里叶红外光谱研究东北黑土开垦对土壤有机质化学结构特征的影响,探明各粒级团聚体及密度组分中有机质化学结构变化特征,为开垦黑土农田土壤有机质结构变化提供理论参考。依托中国科学院海伦农业生态试验站长期定位试验研究平台,以试验开垦前自然草地土壤为对照,选取开垦8年、没有有机物料投入的耕层(0~20 cm)土壤为研究对象,采用湿筛法、密度分组将土壤有机质分成不同组分,用傅里叶红外光谱仪测定原土及各组分有机质红外光谱,分析开垦对土壤有机质化学结构的影响。结果表明:开垦前后,有机质红外结构特征峰相似,均以多糖C—O和醇酚—OH为主。全土芳香族C C含量较开垦前显著减少4.77%,有机质稳定性下降6.32%。在>0.25 mm团聚体中芳香族C=C和羰基C=O相对强度较开垦前分别显著降低29.91%和27.16%,醇酚—OH相对强度显著增加15.60%;0.25~0.053 mm团聚体中,多糖C—O相对强度增加4.57%,脂肪族—CH相对强度显著减少23.85%。<0.053 mm团聚体中,脂肪族—CH相对强度显著减少16.33%。有机质游离态轻组(LF)、闭蓄态组分(OF)中多糖C—O特征峰相对强度分别显著增加15.82%和18.15%,在矿质态组分(MF)中变化不显著。主成分分析表明,开垦对>0.053 mm粒级团聚体和LF、OF组分有机质结构影响最大,各官能团中多糖C—O相对强度增加最明显。综上,开垦使黑土大团聚体和LF的有机质芳香族组分减少,有机质结构趋于简单化,有机质结构稳定性下降。

Based on Fourier transform infrared spectroscopy,the influence of reclamation on the chemical structure characteristics of soil organic matter in black soil of Northeast China was studied,and the chemical structure change characteristics of organic matter in each particle size aggregate and density component were explored,which provided a theoretical reference for the change of soil organic matter structure in black soil farmland.Based on the long-term positioning experimental research platform of Hailun Agro-ecological Experimental Station of the Chinese Academy of Sciences,the natural grassland soil before reclamation was taken as the control,and the soil of plough layer(0~20 cm)for eight years after reclamation with no organic material input was selected as the research object.The soil organic matter was divided into different components by wet sieving method and density grouping.The infrared spectra of original soil and organic matter of each component were determined by Fourier infrared spectrometer,and the influence of reclamation on the chemical structure of soil organic matter was analyzed.The results showed that the infrared structural peaks of organic matter before and after reclamation were similar,and polysaccharide C-O and phenol-OH were the main components.The content of aromatic C=C in the whole soil significantly decreased by 4.77%compared with that before reclamation,and the stability of organic matter decreased by 6.32%.In>0.25 mm aggregates,the relative strength of aromatic C=C and carbonyl C=O decreased by 29.91%and 27.16%,respectively,and the relative strength of enol-OH increased by 15.60%.In 0.25~0.053 mm aggregates,the relative strength of polysaccharide C-O increased by 4.57%,and the relative strength of aliphatic-CH decreased by 23.85%.In<0.053 mm aggregates,the relative strength of aliphatic-CH decreased by 16.33%.The relative intensity of polysaccharide C-O characteristic peaks in free light fraction(LF)and closed storage fraction(OF)of organic matter increased by 15.82%and 18.15%,respectively,and there was no significant change in mineral fraction(MF).Principal component analysis showed that reclamation had the greatest effect on>0.053 mm aggregate and organic matter structure of LF and OF fractions,and the relative strength of polysaccharide C-O in each functional group increased most obviously.In conclusion,reclamation reduces the aromatic components of organic matter in black soil large aggregates and light fractions,the organic matter structure tends to be simplied,and decreased the stability of organic matter structure.