Simulation of recurring defoliation by multiple insects shows lasting consequences for carbon storage in temperate oak forests
| Authors: | Jane Foster, Robert M. Scheller, Brian R. Sturtevant, Philip A. Townsend, Brian Miranda, David J. Mladenoff |
| Year: | 2026 |
| Type: | Scientific Journal |
| Station: | Southern Research Station |
| DOI: | https://doi.org/10.1016/j.foreco.2025.123450 |
| Source: | Forest Ecology and Management |
Abstract
Insect defoliation outbreaks are dynamic forest disturbances that alter species composition and carbon balance. In the Central Appalachian Mountains, U.S.A., the invasive spongy moth (SM, Lymantria dispar L., formerly called gypsy moth) has been spreading and impacting oak forests for 45 years, yet much about how its outbreaks compound the effects of native defoliator inhabitants remains unknown. We developed a model to simulate insect defoliation and project long-term consequences on forest biomass and composition. The model incorporates outbreak spatial dynamics derived from Landsat data and implements species-specific tree-growth and mortality responses. We used this model with the LANDIS-II forest change model to simulate forest dynamics over 400 years in a managed forest in western Maryland, with and without SM defoliation, to quantify changes that follow invasion. Additional scenarios included a native defoliator, forest tent caterpillar (FTC, Malacosoma disstria Hbn.), to examine how multiple defoliators alter disturbance outcomes. Results showed that SM invasion changed forest species composition in unexpected ways. Shade tolerant species increased less after SM invaded, even though they were not preferred hosts, due to their proximity to neighboring host species. Forest carbon was temporarily reduced following individual outbreaks, and long-term aboveground C was lower (by 7.2 Mg C ha 1 on average), with SM than without. Changes in forest aboveground C stocks were more pronounced when a native defoliator was included, particularly when outbreaks synchronized. Interacting insect disturbances have significant consequences for forest C storage and should be incorporated into our growing understanding of C dynamics at landscape scales.