Hay-scented fern (Dennstaedtia punctilobula (Michx.) Moore) interference with growth of northern red oak (Quercus rubra L.) seedlings.

We assessed the impacts of hay-scented fern (Dennstaedtia punctilobula (Michx.) Moore) and subsoil liming (CaO amendments) on root and shoot growth of greenhouse-grown, first-year, northern red oak (Quercus rubra L.) seedlings. Red oak seedlings and ferns were grown in reconstructed soil profiles of four common Pennsylvanian forest soils. When grown in the presence of hay-scented ferns, with or without subsoil liming, red oak seedlings had significantly reduced height growth, and foliar, stem and total root biomass. Fern foliar biomass was significantly reduced when ferns were grown with red oaks, but there was no significant difference in total belowground biomass of ferns. Belowground fern biomass was concentrated in the upper soil profile, whereas red oak roots showed a variety of distributions. In the presence of ferns, fine root branching in red oak was reduced in the organic horizons of three of the four soils tested. In both the presence and absence of ferns, root branching in red oak was also significantly and negatively correlated with the concentration of 0.01 M SrCl(2)-extractable aluminum in the mineral horizons (r(2) = 0.77). Subsoil liming generally improved root branching in red oaks. The presence of ferns significantly reduced ectomycorrhizal infection frequency in red oak. We conclude that hay-scented fern inhibited root branching and suppressed above- and belowground biomass accumulation of first-year northern red oak seedlings.