冻融作用对大兴安岭多年冻土区泥炭地土壤有机碳矿化的影响研究

摘要

冻融循环是影响土壤碳氮生物地球化学过程较为重要的因素.在全球变化背景下,冻融作用对冻土区土壤碳库稳定性及其关键生物地球化学过程影响研究是当前国际热点,尤其是冻融作用影响下多年冻土区泥炭地土壤有机碳矿化研究目前仍未明确.选取我国大兴安岭多年冻土区泥炭地表层(0~15cm)和深层(15~30cm)土壤,采用冻融试验及室内培养方法,探索分析了冻融作用影响下泥炭地土壤有机碳矿化特征,并从土壤活性碳和土壤酶活性角度阐述了影响机制.结果表明在短期的培养中,土壤有机碳矿化量在483~2836mg/kg间波动,而冻融循环均显著降低了表层和深层土壤有机碳矿化量,并且对深层土壤有机碳的矿化抑制作用更为明显,高达76%.值得注意的是,冻融循环却明显促进了CH4的排放,尤其是表层土壤,高达145%.冻融循环作用也显著增加了土壤可溶性有机碳(DOC)含量,但却降低了土壤微生物量碳(MBC)以及土壤纤维素酶、淀粉酶和蔗糖酶活性.冻融作用下低的土壤酶活性以及相对低质量碳是抑制土壤有机碳矿化的原因.全球变暖背景下,与单纯温度增加所导致的土壤有机碳矿化释放量相比,冻融循环作用能降低大兴安岭泥炭地活动层中土壤有机碳在短期内碳的释放.%Freezing-thawing process is an important factor controlling carbon dynamics in mid-high latitude regions. Recently,there has been a growing interest in the effects of freezing-thawing cycle (FTC) on soil carbon stability and associated bio-geochemical process in mid-high latitude regions under global warming. The effects of FTC on soil organic carbon mineralization in peatland of permafrost region are still unclear. In this study,we collected soil samples from active layer (0-15 cm and 15-30 cm) of an undisturbed permafrost peatland in the Great Hinggan Mountains,Northeast China,and then subjected them to FTC simulation and mineralization incubation experiments. Our goal was to characterize soil mineralization in peatland by FTC and to determine the corresponding influencing factors. The results showed that cumulative organic carbon mineralization including CO2and CH4ranged from 483 mg/kg to 2836 mg/kg. FTC significantly decreased peatland soil organic carbon mineralization in 0-15 cm and 15-30 cm layers,especially for the 15-30 cm soil layer that the decrease magnitude reached up to 76%. Notably,FTC obviously promoted CH4emission,and the emission in 15-30 cm soil layer increased by up to 145%. Meanwhile,FTC significantly increased soil dissolved organic carbon (DOC) concentration,but reduced microbial biomass carbon (MBC) concentration and amylase,cellulase and sucrase activities. Lower enzyme activities and relatively inferior quality carbon were the reasons for the decreased soil organic mineralization in FTC treatment. Under global warming,compared with the effect of only temperature increase,FTC can decrease the soil organic carbon mineralization during the short incubation stage in the permafrost peatland of Great Hinggan Mountains.