[Effects of wetland reclamation on amino sugar accumulation in soils of the Sanjiang Plain].

Microbial residues play important roles in the formation and stabilization of soil organic matter. The responses of soil microbial residues to wetland reclamation, however, remain unclear. In this study, we collected soil samples from a native wetland dominated by Calamagrostis angustifolia as well as three agricultural lands cultivated for 5, 15, and 25 years to examine the effects of wetland reclamation on the content of microbial residues (amino sugar analysis). Results showed that soil amino sugar contents were significantly reduced after wetland reclamation, with a positive relationship between the reduction and the duration of reclamation. After 25 years of reclamation, the content of glucosamine, galactosamine, and muramic acid in agricultural soils decreased by 38.0%, 38.1%, and 35.9%, respectively, compared to the natural wetland. The reduction of muramic acid (25.8%) was stronger than glucosamine (14.9%) after 5 years of reclamation, indicating that bacterial-derived microbial residues were more sensitive to wetland reclamation than fungal-derived counterparts in the short term. Total amino sugars were decreased by 21.1%, 34.0%, and 38.0% after 5, 15, and 25 years of wetland reclamation, respectively. The proportion of total amino sugars in soil organic matter was significantly decreased from 4.8% in natural wetland to 4.4% after 25 years of reclamation, indicating that long-term wetland reclamation accelerated the depletion of microbial-derived organic components, and thus changed the composition of soil organic matter. Such changes may affect long-term stabilization of soil organic matter and ecosystem functioning.微生物残体在土壤有机质的形成和稳定过程中发挥着重要作用,但湿地开垦对土壤微生物残体积累特征的影响尚不清楚。本研究以三江平原小叶章湿地为对象,采集原始自然湿地和开垦改种豆科作物后不同耕作年限(5年、10年和25年)的土壤,以氨基糖为微生物残体的标识物,探讨湿地开垦对土壤微生物残体积累特征的影响。结果表明: 自然湿地开垦为农田后显著降低了土壤中氨基糖的含量,且随着开垦年限的增加,氨基糖的损失比例也增加。与自然湿地相比,开垦25年后土壤中的氨基葡萄糖、氨基半乳糖和胞壁酸含量分别下降38.0%、38.1%和35.9%,且在开垦最初5年中细菌来源的胞壁酸下降速率(25.8%)远高于真菌来源的氨基葡萄糖(14.9%),说明短期内湿地开垦对细菌的影响较真菌更加迅速。湿地开垦为农田5、15和25年后,土壤氨基糖总量分别下降21.1%、34.0%和38.0%;同时,氨基糖总量占土壤有机质的比例也受到湿地开垦的显著影响,由自然湿地中的4.8%降至开垦25年后的4.4%。这说明长期湿地开垦加速了土壤有机质中微生物来源有机组分的分解转化,进而改变土壤有机质的组成。这些变化将影响湿地生态系统中土壤有机质的长期稳定和功能演变。.