The Effects of Burn Frequency on the Density of Some Grasshoppers and Leaf Miners in a Florida Sandhill Community

Abstract

The frequency and intensity of wildfires are known to affect plant diversity and growth. We examined whether the periodicity of burning affected the density of insect herbivores. A Florida sandhill community in West-Central Florida was divided into ten sections, two sections of which each had a different periodicity of burning: one year, two years, five years, seven years, and control (zero years). Each burn cycle had been repeated many times, but all plots had been burnt in the summer of 1996, three months prior to the onset of our study. We censused the most common herbivores of the low-growing herbs: grasshoppers, and the most common herbivores of the trees: leaf miners, every month for a year. Grasshoppers were counted on two common flowering plants in the community, Carphephorus corymbosus (Nutt.) Torrey & A. Gray, and Eriogronum tomentosum, Michaux. Leaf miners were counted on the two most common trees, Quercus geminata, Small, and Quercus laevis, Walter. Grasshopper densities were significantly higher on the flowering plants in the 1 year, 2 year, and 5 year burned plots than on the 7 year or control plots. Leaf miner densities on the oaks were not significantly different between treatments. The differences in grasshopper densities could be due to a higher density of forbs and the occurrence of healthier forbs in the more frequently burned plots.