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| Carbon cycle models often lack explicit belowground organism activity, yet belowground
organisms regulate carbon storage and release in soil. Ectomycorrhizal fungi are important players in the
carbon cycle because they are a conduit into soil for carbon assimilated by the plant. It is hypothesized that
ectomycorrhizal fungi can also be active decomposers when plant carbon allocation to fungi is low. Here,
we reviewed the literature on ectomycorrhizal decomposition and we developed a simulation model of the
plant-mycorrhizae interaction where a reduction in plant productivity stimulates ectomycorrhizal fungi to
decompose soil organic matter. Our review highlights evidence demonstrating the potential for
ectomycorrhizal fungi to decompose soil organic matter. Our model output suggests that ectomycorrhizal
activity accounts for a portion of carbon decomposed in soil, but this portion varied with plant productivity
and the mycorrhizal carbon uptake strategy simulated. Lower organic matter inputs to soil were largely
responsible for reduced soil carbon storage. Using mathematical theory, we demonstrated that biotic
interactions affect predictions of ecosystem functions. Specifically, we developed a simple function to
model the mycorrhizal switch in function from plant symbiont to decomposer. We show that including
mycorrhizal fungi with the flexibility of mutualistic and saprotrophic lifestyles alters predictions of
ecosystem function. | |
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