Linking conservation implications of modified disturbance regimes, plant communities, plant associations, and arthropod communities.

Modifications to disturbance regimes have landscape-level effects on plant communities and have the potential to influence organisms at multiple trophic levels. We examined differences in the arthropod community across a gradient of oak/hickory dominance, a plant community maintained by disturbance such as periodic fires and extensive land clearing. In southern Illinois, we used patches of forest that varied in tree dominance ranging from 94 to 0% oak/hickory composition dependent on prior land usage that occurred > 50 years ago at minimum, to test two predictions: (1) oak (Quercus) and hickory (Carya) species contain more arthropod biomass and diversity than mesic tree species [e.g., American beech (Fagus grandifolia) and maples (Acer spp.)] and (2) due to plant associations, arthropod communities are more diverse and abundant on host trees within oak/hickory stands than non-oak/hickory stands. Our results were consistent with the prediction that arthropod biomass, guild Shannon diversity, and guild richness are higher on oaks, hickories and tulip tree (Liriodendron tulipifera) than beech and maples. We also found support for the prediction that due to plant associations, % non-oak/hickory stand composition negatively influenced arthropod guild Shannon diversity and guild richness on host trees, including maples and beech. These results are the first to demonstrate that modified disturbance regimes can influence multiple trophic levels both directly due to species-specific variation in susceptibility of plants to herbivory and indirectly through effects of plant associations. This result is concerning as modified disturbance regimes are influencing large-scale plant community composition among biomes worldwide.