菌根真菌对土壤呼吸的影响

Influence of mycorrhizal fungi on soil respiration

土壤是陆地生态系统的重要组成部分,是地球最大的碳库之一。土壤呼吸是陆地生态系统向大气释放CO2的主要途径之一,其微小的变化将导致大气CO2浓度的较大波动。菌根是土壤真菌与植物根系形成的共生体,存在于绝大多数植物(90%)的根系和生境中。菌根共有7种类型,其中,在自然界中以丛枝菌根和外生菌根为主。众多研究表明,菌根对土壤呼吸有着至关重要的影响,是预测土壤CO2释放速率必须考虑,但却是难以估算的因素。文章总结了有关菌根(包括丛枝菌根和外生菌根)对土壤呼吸影响的研究进展,对目前所得到的研究结果进行了分析,表明菌根真菌侵染植物根系形成菌根后,能提高土壤呼吸的速率,其可能的途径有3条:(1)增强了根系的呼吸,(2)菌根真菌自身呼吸的组分,(3)根外菌丝促进了非根际区土体的呼吸。但是,菌根侵染对根系呼吸敏感性(Q10)影响的研究,大多数则表现为不显著。同时,菌根对土壤呼吸的影响受到各种因素的制约。通过对不同温度下菌根真菌呼吸速率的分析,表明菌根真菌对温度的升高具有适应性。从目前已发表的报道来看,目前关于菌根对土壤呼吸影响的研究还非常少,但可喜的是,近年来,越来越多的研究已经意识到了菌根在土壤呼吸中的重要作用。准确评估菌根在土壤呼吸中的贡献,将有助于预测未来在气候变化下,土壤CO2的排放量。

Soil, as a main part of terrestrial ecosystem, is one of the planet＇s largest carbon reserves, and soil respiration is one of the largest CO2 fluxes from terrestrial biosphere to the atmosphere. The slim change of soil respiration will lead to the dramatic fluctua- tion of the atmospheric CO2 concentration. In terrestrial ecosystems, symbiotic associations between plant roots and mycorrhizal fungi are near ubiquitous, with 90 per cent of all plant species forming mycorrhizas. At the global scale, although there are seven type mycorrhizas, plants with arbuscular mycorrhizas （AM） and Ectomycorrhizas （EM） are the dominant components of the major world biomes today. A few studies have testified that mycorrhizas including AM and EM play indispensable role in soil respiration while it is difficult to be determined. The advances in the influence on myeorrhizas to soil respiration were summarized in this paper. The results have shown that mycorrhizas have greater enhancement on the soil respiratory and minor influence on temperature sensitivity （Q10）. The possible ways included （1） to improve the respiration of plant roots, （2） to consider mycorrhizas as a component of respi- ration, and （3） to enhance the respiration in bulk soil. Furthermore, the mycorrhizal function in soil respiration is affected by all kinds of factors including biotic and abiotic factors. Mycorrhizal external hyphae expressed the acclimation to the temperature. The reports about the mycorrhizal contribution to soil respiration are by far comparatively few. Recently, the key role of myeorrhizas in soil res- piration has been gradually recognized. It will be helpful for us to predict the CO2 flux from soil during the climatic changes if my- corrhizal roles in soil respiration are examined properly