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 ...1. 细根与菌根（mycorrhiza）通常是土壤碳（C）输入的最主要来源，因此与土壤碳平衡密切相关。此前已有研究发现，丛枝菌根（arbuscular mycorrhizal, AM）真菌可促进凋落物分解，进而可能降低土壤碳库储量，但此类研究多聚焦于相对较高用量的高质量凋落物的快速分解过程，因此在多数长期生态场景中其结论未必成立。 2. 本研究针对土壤中真实用量的高丰度13C/15N标记根凋落物，探究了菌根真菌对其中碳（C）与氮（N）归趋的影响。该凋落物以新鲜状态，或经野外条件下3个月培养后的状态，被添加至菌丝生长芯（hyphal in-growth core）中；通过轮作处理，芯内菌根丰度可被降低或维持原状。在温室条件下与植物共培养3个月后，我们测定了经翻转处理的菌丝生长芯内残留的13C与15N含量，以及……