Slowed decomposition in ectomycorrhizal ecosystems is independent of plant chemistry

Ecosystems dominated by plants in symbiosis with ectomycorrhizal fungi store more carbon in soils. There is increasing evidence that this may be due to competition between primary producers and microbial decomposers for soil nitrogen, mediated by ectomycorrhizal fungi. This competitive interaction inhibits decomposition and increases soil carbon storage. However, other work suggests elevated carbon storage is due to recalcitrant plant tissue chemistry in ectomycorrhizal ecosystems, rather than ectomycorrhizal competition for soil nitrogen. These two frameworks make similar predictions for soil carbon storage, making them difficult to distinguish empirically. Here I argue that the ectomycorrhizal-recalcitrance hypothesis is not well supported by recent developments in the understanding of soil carbon chemistry, or evolutionary relationships among ectomycorrhizal plants. Therefore, differences in input chemistry are not sufficient to discount alternative mechanisms of carbon stabilization in ectomycorrhizal ecosystems. Future work on EM-specific stabilization of soil C should focus on alternative mechanisms including competition for N, direct antagonistic interactions, and other microbial community driven mechanisms. (C) 2016 Elsevier Ltd. All rights reserved.