Data from: Earthworms affect growth and competition between ectomycorrhizal and arbuscular mycorrhizal plants

Previous research showed that during intermediate stages of primary
succession, when vegetation is dominated by ectomycorrhizal (EcM) shrubs
and trees, site colonization by earthworms substantially alters plant
communities. Research has also shown that EcM shrubs and trees suppress
arbuscular mycorrhizal (AM) plants in the understory. To determine whether
earthworm activity reduces this asymmetric competition, we conducted a
full factorial laboratory experiment in which we grew EcM Betula pendula
and AM Tripleurospermum inodorum, together or apart, in soils affected or
not affected by earthworms. When both plants were grown together in soil
unaffected by earthworms, growth of T. inodorum was significantly reduced
by competition with B. pendula, but B. pendula growth was not reduced by
T. inodorum. In soil affected by earthworms, the growth of both species
was increased, and the negative effect of B. pendula on T. inodorum was no
longer statistically significant (P < 0.05). These data indicate
that earthworms weaken the asymmetric competition between EcM and AM
plants. Consistent with this inference, EcM colonization of B. pendula was
decreased and AM fungal bioassay in soil was increased by earthworms.