A significant fraction of the terrestrial biosphere has a history of agricultural use, and this fraction is expected to increase as agricultural land continues to be abandoned. Legacies from historic agriculture can have persistent ecological effects by altering soil conditions and plant communities for decades after abandonment, even after restoration techniques are implemented. Despite well-documented effects of historic agriculture on soils and plants, less work has examined how agricultural legacies might affect insect community composition or rates of insect herbivory. The current extent of the longleaf pine ecosystem occurs largely on abandoned agricultural land that concurrently experiences wide scale fire suppression. Prescribed fires and canopy thinning are often used to aid in the recovery of understory plant communities in these post-agricultural habitats. We used a large-scale field study to evaluate how fire frequency and canopy thinning affects insect (grasshopper) community composition and herbivory rates in remnant and post-agricultural longleaf pine woodlands in the southeastern USA.
Our results demonstrate that historic land use may create persistent differences in the composition of grasshopper assemblages, whereas prescribed fire and canopy thinning may be important for determining the abundance of grasshoppers, largely through changes to light availability and plant cover. Therefore, our results suggest that changes in contemporary management regimes (e.g., increasing prescribed fire) may not be sufficient to shift the structure of grasshopper communities in post-agricultural sites towards communities in remnant habitats. We also found that land-use history and fire frequency affected herbivory rates on a focal plant species, with herbivory rates being greater in more disturbed habitats (e.g. post-agricultural habitats and fire-suppressed remnant woodlands). Changes in herbivore communities and herbivory rates may thus potentially limit the recovery or restoration of post-agricultural or fire-suppressed habitats by reducing the establishment or performance of some plant species. Overall this work highlights that agricultural activities abandoned decades ago can have long-lasting effects on consumer-mediated ecosystem processes.