水位影响泥炭沼泽土壤有机碳分解的生物化学机制研究进展

Biochemical mechanism of soil organic carbon decomposition in peatland during water table change:a review

在人类活动和气候变化影响下,泥炭沼泽生态系统急剧退化,其独特的氧化还原过程使得退化泥炭沼泽及其恢复过程中土壤有机碳(SOC)分解与存储机制成为研究的热点问题。泥炭沼泽排水/再湿过程会显著改变土壤的氧化还原条件,进而改变土壤微生物群落和酶活性,驱动铁氧化还原过程,影响SOC分解。已有研究对“缺氧是维持泥炭地碳存储的关键”的传统理论提出了质疑,而土壤酶及铁(Fe)在土壤SOC分解与存储过程中分别扮演着“酶锁”和“铁门”的作用,二者同时受到氧化还原条件的影响。然而,有关退化泥炭沼泽及其恢复过程中酶-土壤SOC-Fe相互作用及微生物驱动机制还有待深入。总结了干旱/排水/再湿对泥炭沼泽土壤SOC组分、分子结构、碳排放的影响,并从微生物、酶、Fe化学的角度归纳总结了泥炭沼泽土壤SOC分解的生物化学机制。未来研究中应将土壤水分与土壤SOC分解的生物地球化学机制联系起来,探寻水位变化过程中生物及非生物要素对土壤SOC分子结构变化的调控机制及土壤氧化酶-酚类物质/SOC分子结构-水解酶之间的作用机制。同时,关注Fe的氧化和还原过程,评估Fe-SOC在泥炭沼泽土壤有机碳中的地位,利用分子生物学手段探究水位变化过程中酶-SOC分解/碳排放-铁之间的权衡机制。

Peatland ecosystem is rapidly degraded under influence of human activities and climate change.The mechanism of soil organic carbon(SOC)decomposition during the drained and rewetting processes of peatland have become a hot topic due to its unique redox environment.Drainage/rewetting of peatlands significantly changes the soil redox conditions,which would further affect soil microbial community and enzyme activities,drive iron redox process,and finally influence the SOC decomposition process.Recent studies have challenged the traditional theory that anoxia is the key to maintain carbon storage function of peatlands.Soil enzymes and iron,which are both affected by redox conditions,acting as’enzyme latch’and’iron gates’,respectively,in the decomposition and storage of SOC in peatland ecosystems.However,there is an urgent need for further research on the interaction of enzymes,organic carbon,and iron and its microbial driving mechanism during the drainage/rewetting processes of peatlands.This research summarized the effect of drainage/drought/rewetting on the composition and molecular structure of soil SOC and the carbon emission processes.It also summarized the biochemical mechanisms of soil SOC decomposition during the drainage/drought/rewetting processes of peatlands from the aspects of soil microbes,enzymes,and iron chemistry.Future research should link soil moisture with the biogeochemical mechanism of SOC decomposition,explore the mechanisms of biotic and abiotic properties in regulating molecular transformation processes of SOC,reveal the interaction mechanism of oxidase,phenols/SOC molecular structure,hydrolase during the periods of drainage/drought/rewetting.At the same time,future study should focus on the illuminating the trade-off mechanism between enzyme-SOC decomposition/carbon emission-iron during water level change using molecular biology methods combined with the iron REDOX process and the role of Fe-SOC in SOC of peatlands.