Hubbard Brook Experimental Forest: soil, litter, plant and microbial attributes on mycorrhizae litter decomposition plots

Studies show mycorrhizal fungi can influence leaf litter decomposition
in a variety of ways, but the effects of arbuscular mycorrhizal (AM)
fungi and ectomycorrhizal (ECM) fungi on litter decay in forests vary
widely across published reports. We experimentally reduced the
presence of fine roots and their associated mycorrhizal fungi by soil
trenching within a series of plots spanning a gradient of mycorrhizal
dominance containing from 96% AM to 100% ECM-associated trees at
Hubbard Brook Experimental Forest in Woodstock, NH. We incubated four
species of leaf litter in mesh decomposition bags in areas with
reduced access to roots and mycorrhizal fungi and in adjacent areas
with intact roots and mycorrhizal fungi. After 608 days of
decomposition (November 2017 through July 2019), we found that litter
decayed more rapidly in the presence of fine roots and mycorrhizal
hyphae in all plots, regardless of dominant tree mycorrhizal type.
Root and mycorrhizal exclusion did not affect enzyme activities on
decomposing litter or soil microbial community composition. Despite
reports that both AM and ECM fungi may reduce litter decay rate, our
results indicate that AM and ECM-associated fine roots stimulate
litter decomposition.