Fire effects on insect herbivores in an oak savanna: the role of light and nutrients

1. Environmental heterogeneity created by prescribed burning provided the context for testing whether the distribution of an oak specialist (the lace bug, Corythuca arcuata) could be explained by stoichiometric mismatches between herbivore and host plant composition. 2. Field observations showed that lace bug density was seven-fold higher in frequently burned than in unburned units. 3. Lace bug density did not increase with leaf nutrient concentrations, but was instead associated with higher light levels, higher concentrations of leaf carbon (C), lignin and total phenolics, and lower levels of cellulose. In addition, lace bugs reared on high-light leaves had higher levels of survivorship than those fed on low-light leaves. 4. Sampling restricted to full-sun leaves was used to test whether fire-related changes in leaf nitrogen (N) and phosphorus (P) concentrations have a secondary influence on lace bug success. This sampling provided only limited evidence for nutrient limitation, as decreases in leaf N and P were associated with an increase in lace bug mass but a decrease in density. 5. It is concluded that burning probably promotes lace bug population growth by increasing canopy openness, light penetration, and the availability of C-based metabolites, and thus simple stoichoimetric mismatches between herbivores and host plants are not of primary importance in this system.