菌根真菌在陆地生态系统碳循环中的作用

Involvements of mycorrhizal fungi in terrestrial ecosystem carbon cycling

在陆地生态系统中,土壤、植被与大气之间有着可观的碳交换通量,陆地生态系统碳循环也和全球气候变化密切关联。菌根真菌可与绝大多数陆地植物建立菌根共生关系,通过矿质养分-碳交换连接起生态系统地上与地下部分,深度参与和影响陆地生态系统的碳循环过程。该文从碳的输入,土壤有机质的形成、稳定和分解等4个关键环节分别论述了菌根真菌在陆地生态系统碳循环中的作用。研究表明,菌根真菌在陆地生态系统碳的输入过程中扮演关键角色,其通过改善植物矿质营养,参与植物逆境响应,影响植物的光合作用强度,以及调控植物多样性与生产力之间的关系等多种途径,维持或提高植被初级生产力;大气中的CO_(2)被植物固定后,一部分碳经由菌丝网络输送到土壤中,随后经微生物的分解和转化,与矿物结合或被团聚体包裹而被稳定在土壤中;同时,菌根真菌通过影响根际激发效应和菌丝际生物化学过程,如分泌特定胞外酶,与菌丝际微生物互作,驱动芬顿反应,以及与腐生微生物竞争等,调控土壤有机质的分解和转化过程。考虑到菌根真菌对环境和气候变化的敏感性,该文还探讨了全球变化因子对菌根真菌介导的碳循环过程的影响。最后,该文对未来研究方向进行了展望,并提出以下建议:依托联网研究,全面解析菌根真菌参与陆地生态系统碳循环的机理过程及其环境依赖性;加强定量研究,将菌根真菌的作用纳入生态系统碳循环模型;构建菌根应用技术体系,推进菌根真菌的生态和农业应用,提升陆地生态系统“碳汇”功能,为实现国家碳中和目标和应对气候变化提供可选择的技术方案。

There are substantial carbon exchange fluxes among soil,vegetation and atmosphere in the terrestrial ecosystems,which are highly relevant to global climate changes.Mycorrhizal fungi can form symbiotic associations with most terrestrial plants,linking the above-and below-ground ecosystems through mineral nutrient-carbon exchange;thus,mycorrhizal fungi play crucial roles in terrestrial carbon cycling.This review summarized the involvements of mycorrhizal fungi in the terrestrial carbon cycling processes,including the carbon input,and formation,stabilization,and decomposition of soil organic matter.Studies have demonstrated that mycorrhizal fungi markedly influence the terrestrial carbon input processes by alleviating plant nutrient deficiencies,improving plant stress resistance,influencing plant photosynthesis,and regulating plant diversity-productivity relationships,subsequently sustaining or improving primary productivity of terrestrial vegetation.A considerable proportion of photosynthetic carbon is channeled directly into the soil matrix via the fungal mycelial network,where it is partly converted into microbial-derived organic carbon,further changes the composition of soil organic carbon,and be stabilized through association with minerals and/or forming soil aggregates.Mycorrhizal fungi can affect the decomposition and transformation of soil organic matter mainly through two mechanisms:the rhizosphere priming effects and/or hyphosphere biogeochemical processes.These mechanisms involve the secretion of specific extracellular enzymes,shaping hyphosphere microbial communities,induction of chemical oxidation,and competition for limited resources(e.g.,nutrients and water)with free-living saprotrophs.Considering the sensitivity of mycorrhizal fungi to environmental and climate changes,we also discuss the impact of global change factors on soil carbon cycling mediated by mycorrhizal fungi.Finally,we proposed future research directions,emphasizing a need for in-depth studies on the role of mycorrhizal fungi in terrestrial carbon cycling and their environmental dependence based on network experiments in typical ecosystems.Quantitative studies should be strengthened to integrate mycorrhizal fungi into ecosystem carbon cycling models,and mycorrhizal technologies should be developed and practiced in ecological restoration and agriculture to facilitate terrestrial carbon sequestration for achieving the national carbon neutrality goals and combating climate changes.