Do arbuscular mycorrhizal fungi stabilize litter-derived carbon in soil?

1. Fine roots and mycorrhiza often represent the largest input of carbon (C) into soils, and are therefore of primary relevance to the soil C balance. Arbuscular mycorrhizal (AM) fungi have previously been found to increase litter decomposition which may lead to reduced soil C stocks, but these studies have focused on immediate decomposition of relatively high amounts of high-quality litter and may therefore not hold in many ecological settings over longer terms. 2. Here we assessed the effect of mycorrhizal fungi on the fate of C and nitrogen (N) contained within a realistic amount of highly 13C/15N labelled root-litter in soil. This litter was either added fresh or after a 3-month incubation period under field conditions to a hyphal in-growth core where mycorrhizal abundance was either reduced or not through rotation. After three months of incubation with a plant under greenhouse conditions, the effect of turning cores on residual 13C and 15N inside the cores was measured, as well as ...