Data from: Plant diversity enhances moth diversity in an intensive forest management experiment

Intensive forest management (IFM) promises to help satisfy increasing
global demand for wood, but may come at the cost of local reductions to
forest biodiversity. IFM often reduces early seral plant diversity as a
result of efforts to eliminate plant competition with crop trees. If
diversity is a function of bottom-up drivers, theory predicts that
specialists at lower trophic levels (e.g., insect herbivores) should be
particularly sensitive to reductions in plant diversity. We conducted a
stand-level experiment to test bottom-up controls on moth community
structure, as mediated by degrees of forest management intensity. Using a
dataset of 12,003 moths representing 316 moth species, moth richness
decreased only slightly, if at all, as herbicide intensity increased (P =
0.062); the ’moderate’ treatment, which is most commonly applied in the
northwestern USA, was estimated to have 4.72 (± 2.14 SE, P =0.039) fewer
species than the control. Structural equation modeling revealed strong
support for an effect of herbicide on plant abundance, which influenced
plant species richness and subsequently moth species richness. Moth
species richness was associated with plant species richness and followed a
power law function (z=0.42, P =0.006), which is surprisingly consistent
with a recent large-scale experiment in agricultural systems, and provides
support for bottom-up drivers of moth community structure. Moth abundance
was not influenced by the direct effects of silvicultural herbicide
treatments. Site-level effects and variation in pre-harvest vegetation
communities resulted in residual broadleaf and herbaceous vegetation in
even the most intensive treatment. Even at low densities, these residual
deciduous and herbaceous plants supported higher-than-expected moth
abundance and richness. We conclude that forest management practices that
retain early seral vegetation diversity are the most likely to conserve
moth communities.