Since 1880, Earth's average temperature has increased by about 0.9oC (1.6oF). End-of-Century temperatures may be 5.4oC warmer. Soil warming experiments have examined impacts of increased temperatures on soil microbes and vegetation, but few examined macroinvertebrate fauna. In these select previous experiments, invertebrate herbivory increased in response to warming. However, these studies occurred in northern, less weathered, more fertile soils that are biogeochemically different from weathered soils of the sub/tropics, including the southeastern Piedmont of the US. In this study, we investigated the potential invertebrate herbivory responses to increased temperature in a soil warming study using twelve 18-m2 plots in the Whitehall Forest of Athens, GA. Leaf samples and visual invertebrate herbivory observation data were collected in July 2018. Data from seedlings and saplings of four tree species were used: Quercus rubra, Q. alba, Acer rubrum, and A. floridanum. We analyzed the visual herbivory data to assess any variation among the ambient-temperature, +3oC, and +5oC soil warming plots. We hypothesized that there would be higher rates of foliar invertebrate herbivory in the warmed plots.
Results/Conclusions
Preliminary results indicated that invertebrate herbivory rates did not respond to soil warming in southeastern Piedmont soils. There were no significant differences in visual herbivory from June, August, and October across the ambient, +3oC and +5oC plots. For example, in August 2018, a single-factor ANOVA showed that there was no significant difference in averages of herbivory among the ambient (7.33±0.437), +3oC (6.920±0.847), and +5oC (7.794±0.932) plots (p=0.783). However, ectomycorrhiza-associated tree species had significantly higher herbivory rates than arbuscular mycorrhiza species (p<0.0001). Our results suggest that plant and invertebrate herbivore interactions in the southeastern Piedmont, and responses to soil warming, depend on mycorrhizal fungal associates.