Implementation of mycorrhizal mechanisms into soil carbon model improves the prediction of long-term processes of plant litter decomposition

[摘要] Ecosystems have distinct soil carbon dynamics, including litterdecomposition, depending on whether they are dominated by plants featuringectomycorrhizae (EM) or arbuscular mycorrhizae (AM). However, current soilcarbon models treat mycorrhizal impacts on the processes of soil carbontransformation as a black box. We re-formulated the soil carbon model Yasso15 and incorporated impacts ofmycorrhizal vegetation on topsoil carbon pools of different recalcitrance.We examined alternative conceptualizations of mycorrhizal impacts ontransformations of labile and stable carbon and quantitatively assessed theperformance of the selected optimal model in terms of the long-term fate ofplant litter 10 years following litter input. We found that mycorrhizal impacts on labile carbon pools are distinct fromthose on recalcitrant pools. Plant litter of the same chemical compositiondecomposes slower when exposed to EM-dominated ecosystems compared toAM-dominated ones, and across time, EM-dominated ecosystems accumulate morerecalcitrant residues of non-decomposed litter. Overall, adding ourmycorrhizal module into the Yasso model improved the accuracy of thetemporal dynamics of carbon sequestration predictions. Our results suggest that mycorrhizal impacts on litter decomposition areunderpinned by distinct decomposition pathways in AM- and EM-dominatedecosystems. A sensitivity analysis of litter decomposition to climate andmycorrhizal factors indicated that ignoring the mycorrhizal impact ondecomposition leads to an overestimation of climate impacts on decompositiondynamics. Our new model provides a benchmark for quantitative modelling ofmicrobial impacts on soil carbon dynamics. It helps to determine therelative importance of mycorrhizal associations and climate on litterdecomposition rate and reduces the uncertainties in estimating soil carbonsequestration.

[学科分类] 大气科学