黄河三角洲滨海湿地不同盐分质量浓度下土壤微生物死亡残体的差异

Variation of Soil Microbial Residues Under Different Salinity Concentrations in the Yellow River Delta

利用微生物生物标识物(氨基糖),探讨盐分对黄河三角洲滨海湿地土壤微生物残体以及微生物残体对土壤有机碳(SOC)库贡献的影响。在滨海湿地生态系统中,随着土壤盐分增加,微生物死亡残体及其对SOC的贡献显著降低,表明高盐滨海湿地不利于土壤微生物死亡残体的积累及其对SOC的贡献。增加的盐分降低了土壤真菌死亡残体与细菌死亡残体的比值。线性回归分析指出土壤含水量、SOC、总氮(N)、交换性钙离子以及真菌死亡残体/细菌死亡残体与微生物死亡残体对SOC的贡献显著正相关。在低盐滨海湿地,良好的土壤条件(如高的水分、SOC和N)通过增加微生物死亡残体的积累和稳定性,促进了SOC的存储;而在高盐滨海湿地,低的可利用碳抑制了微生物死亡残体对SOC的贡献。另外,从低盐到高盐滨海湿地,真菌死亡残体对SOC的贡献逐渐下降,而细菌死亡残体对SOC的贡献没有变化,表明真菌死亡残体的积累对SOC的存储具有较大的影响。

In this study,we explored the effects of salinity on microbial residues(represented by amino sugar)and the contribution of microbial residues to soil organic carbon(SOC)pool under coastal wetlands in the Yel-low River Delta.In addition,we examined how soil physicochemical properties influence microbial residues contribution to SOC.Generalized linear models were used to assess the relationships among microbial residues contribution to SOC,the ratio of fungal residues to bacterial residues,and soil physicochemical properties.The gradually increased soil salinity resulted in the decline in amino sugars,microbial residues(including fungal and bacterial residues)and the contribution of microbial residues to SOC,which indicated that coastal wet-lands with high salinity restrain microbial residues retention in SOC pool.The ratio of fungal residues to bac-terial residues was decreased across increased soil salinity,implying that fungi was sensitive to salinity stress,and bacteria had stronger tolerance to salinity stress.Linear regression analyses showed that soil water content,SOC,soil N,Caexe and fungal residues/bacterial residues were positively related with microbial residues contri-bution to SOC.The fine soil condition(e.g.high water level,SOC and N contents)increased the accumulation of microbial residues,promoting SOC storage of coastal wetlands with low salinity concentration.However,high salinity stress greatly decreased the contribution of microbial residues to SOC,which was associated with low available C substrate in coastal wetlands with high salinity concentration.Additionally,increased salinity induced the decline in the contribution of fungal residues to SOC,but did not change the contribution of bac-terial residues to SOC.These findings indicated changed fungal residues would substantially influence SOC storage.In this study,we found that low salinity soils had higher microbial residues and its contribution to SOC,while high salinity stress reduced microbial residues and its contribution to SOC under coastal wetlands in the Yellow River Delta.Our study elucidates microbial contribution to SOC pool through residues reservoir in coastal wetlands,and push microbial metabolites to a new application in wetland SOC cycling.