排水对我国两种典型湿地土壤有机碳微生物转化过程的影响

Effect of drainage on microbial transformation processes of soil organic carbon in two typical wetlands of China

湿地储存了全球三分之一的土壤有机碳(SOC),并受到人为排水的强烈影响。然而,排水引起的水位下降对不同湿地碳循环(特别是微生物转化)过程的影响尚不明确。为此,本研究以我国两种典型湿地(贫营养型的大九湖湿地和富营养型的红原湿地)土壤为研究对象,通过添加13C标记葡萄糖的室内培养试验,分析了短期和长期排水对SOC降解、胞外酶活性、微生物碳利用效率(CUE)和微生物碳积累效率(CAE)的影响。结果表明:长期和短期排水显著提高了两种湿地SOC降解速率(从淹水处理的1.47μg C·g^(-1)·h^(-1)升高到排水处理的2.47μg C·g^(-1)·h^(-1))、葡萄糖来源的微生物生物量碳(从0.21 mg C·g^(-1)升高到1.00 mg C·g^(-1))和CAE(从0.29升高到0.73),但未改变CUE(变化范围为0.34~0.86)。长期排水提高了大九湖湿地α-葡萄糖苷酶活性,但降低了红原湿地β-葡萄糖苷酶和酚氧化酶活性。综上,排水主要通过增强微生物胞内代谢过程(包括呼吸)提高湿地土壤“微生物碳泵”作用和效率,同时加速了SOC降解。

Wetlands store one third of global soil organic carbon(SOC)and are strongly affected by artificial drainage.The impact of drainage-induced water-table decline on carbon cycling in different wetlands,particularly microbial transformation processes,remains unclear.To address this knowledge gap,we collected soil samples from two typical wetlands of China(a nutrient-poor bog located in Dajiuhu and a nutrient-rich fen in Hongyuan)and conducted an incubation experiment with the addition of 13C-labeled glucose to analyze the effects of short-and long-term drainage on SOC decomposition,extracellular enzyme activity,microbial carbon use efficiency(CUE),and microbial carbon accumulation efficiency(CAE).The results showed that both short-and long-term drainage significantly increased SOC decomposition rates in both wetlands(from 1.47μg C·g^(-1)·h^(-1)in submerged soils to 2.47μg C·g^(-1)·h^(-1)in drained soils),microbial biomass carbon derived from glucose(from 0.21 mg C·g^(-1)to 1.00 mg C·g^(-1))and CAE(from 0.29 to 0.73),but did not alter CUE(ranging from 0.34 to 0.86).Long-term drainage increasedα-glucosidase activity in the Dajiuhu wetland and decreasedβ-glucosidase and phenol oxidase activities in the Hongyuan wetland.In conclusion,drainage enhanced the‘microbial carbon pump’and its efficiency in wetlands mainly via increasing microbial intracellular metabolism(including respiration),but also accelerated SOC decomposition.