连续外源碳添加对土壤有机碳组分的影响

Effects of Repeated Adding Exogenous Carbon on Soil Organic Carbon Fractions

【目的】农田生态系统中外源碳(根系分泌物、根残体等)会连续不断输入到土壤中,明确连续外源碳输入方式下土壤有机碳的形成和固定特征,为农田土壤固碳提供依据。【方法】本研究以沈阳农业大学长期定位试验站不施肥处理表层(0~20 cm)土壤为研究对象,将13C标记葡萄糖以单次或连续多次(每隔15 d添加一次)的方式添加到土壤中,然后进行室内培养。分别在培养第14、29、57、100和365 d采样,通过分析土壤颗粒有机碳(POC)和矿物结合态有机碳(MAOC)组分中外源碳含量和贡献率,对比单次和连续添加方式对外源碳在土壤有机碳组分中分配的差异,探讨外源碳添加方式对土壤有机碳组分的影响。【结果】单次和连续添加处理土壤MAOC中葡萄糖源碳含量分别在第100 d和第57 d达到最大值,然后随时间增加均呈降低趋势。第365 d,单次添加处理土壤POC和MAOC组分中葡萄糖源碳含量均为连续添加处理的1.50倍;连续添加处理土壤POC和MAOC中葡萄糖碳的贡献率分别为0.10%和0.57%,与单次添加处理相比分别降低了36.20%和31.75%(P<0.05);单次和连续添加处理葡萄糖碳分配到MAOC的比例分别为14.69%和9.78%(P<0.05)。【结论】连续添加方式降低了稳定土壤有机碳的形成,单次添加方式的土壤有机碳固存潜力可能被高估。

[Objective]Exogenous carbon(C),such as root exudates and residues,is continuously input into soils under the farmland ecosystem.Research on the formation and fixation characteristics of soil organic C(SOC)after the repeated input of exogenous C into soil would provide a basis for soil C sequestration in farmland.[Method]In this study,the topsoil(0-20 cm)samples were collected from the plots of no fertilization at the long-term experimental station of Shenyang Agricultural University.The 13C-labeled glucose was added to the soil samples as a single or repeated(once every 15 days)way,and then they were incubated in the laboratory.The sub-samples were collected at the 14th,29th,57th,100th and 365th days of incubation.The contents of particulate organic C(POC)derived from glucose C and that of mineral-associated organic C(MAOC)derived from glucose C were determined and their contribution percentages in these fractions were calculated,in order to differentiate the distribution of exogenous C in SOC fractions between single and repeated additions.[Result]The content of MAOC derived from glucose C reached the maximum value at the 57th day and the 100th day under the single and repeated ways,respectively,and then it decreased with incubation time.At the 365th day,the contents of glucose C derived-POC and glucose C derived-MAOC under the single addition way were 1.50 times those under the repeated addition way;The contribution percentage of glucose C derived-POC in POC and that of glucose C derived-MAOC in MAOC under the repeated addition way were 0.10%and 0.57%,respectively.And they were decreased by 36.20%and 31.75%(P<0.05)compared with single addition way,respectively.About 14.69%and 9.78%of glucose C was allocated to MAOC under the single and repeated ways(P<0.05),respectively.[Conclusion]Repeated addition reduces the formation of exogenous C in SOC fractions,while single addition may overestimates the SOC sequestration potential.