The implications of microbial and substrate limitation for the fates of carbon in different organic soil horizon types of boreal forest ecosystems: a mechanistically based model analysis

[摘要] The large amount of soil carbon in boreal forest ecosystems has thepotential to influence the climate system if released in large quantities inresponse to warming. Thus, there is a need to better understand andrepresent the environmental sensitivity of soil carbon decomposition. Mostsoil carbon decomposition models rely on empirical relationships omittingkey biogeochemical mechanisms and their response to climate change is highlyuncertain. In this study, we developed a multi-layer microbial explicit soildecomposition model framework for boreal forest ecosystems. A thoroughsensitivity analysis was conducted to identify dominating biogeochemicalprocesses and to highlight structural limitations. Our results indicate thatsubstrate availability (limited by soil water diffusion and substratequality) is likely to be a major constraint on soil decomposition in thefibrous horizon (40–60% of soil organic carbon (SOC) pool size variation), while energy limitedmicrobial activity in the amorphous horizon exerts a predominant control onsoil decomposition (>70% of SOC pool size variation).Elevated temperature alleviated the energy constraint of microbial activitymost notably in amorphous soils, whereas moisture only exhibited a marginaleffect on dissolved substrate supply and microbial activity. Our studyhighlights the different decomposition properties and underlying mechanismsof soil dynamics between fibrous and amorphous soil horizons. Soildecomposition models should consider explicitly representing differentboreal soil horizons and soil–microbial interactions to better characterizebiogeochemical processes in boreal forest ecosystems. A more comprehensiverepresentation of critical biogeochemical mechanisms of soil moistureeffects may be required to improve the performance of the soil model weanalyzed in this study.

[学科分类] 地球化学与岩石