Print PageArbuscular mycorrhizal (AM) fungi form symbiotic associations with roots of more than eighty percent of land plants and obtain carbon (C) from their host plants in return for increasing plant acquisition of mineral nutrients. AM fungi have long been believed to facilitate soil C retention through increasing organic C inputs and protecting soil organic C from microbial attack via aggregation. However, emerging evidence has recently showed that AM fungi can also stimulate organic C decomposition. By combining dual stable isotope labeling and hyphae ingrowth techniques, we examined the impact of AM fungi and plant roots on residue decomposition under both ambient and elevated carbon dioxide conditions.
Results/Conclusions
Results from microcosm and field experiments showed that AM fungi significantly increased decomposition of both soil- and residue-derived C and promoted nitrogen transfer from decomposing residues to host plants. Also, enhancement of AM fungi by elevated carbon dioxide stimulated residue decomposition. These results challenge the prevailing paradigm of mycorrhizal protection of organic C in soil and raise questions about current predictions of soil C balance under future climate change scenarios.
