A recent study enabled by the National Genomics Infrastructure shows that ectomycorrhizal fungi play contrasting roles in decomposition of organic matter. The researchers, led by Björn D. Lindahl at Swedish University of Agricultural Sciences (SLU), showed that exclusion of tree roots and associated ectomycorrhizal fungi in a boreal forest increased decomposition of surface litter by 11%. On the other hand, root exclusion seemed to hamper decomposition in the deeper layers of the ground. The findings, published in The ISME Journal, points to the importance of ectomycorrhizal fungi in regulation of below-ground organic matter accumulation.