Forest stand conditions after 13 years of gypsy moth infestation
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In: Gillespie, Andrew R.; Parker, George R.; Pope, Phillip E.; Rink, George: eds. Proceedings of the 9th Central Hardwood Forest Conference; Gen. Tech. Rep. NC-161. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station: 130-144
Of 603 central Pennsylvania plots that were established in 1978 to measure the short-term impact of repeated gypsy moth (Lymantria dispar) defoliation, 228 were selected for continued study in 1985. Individual observations of defoliation and tree vigor were continued through 1992. Although two gypsy moth outbreaks occurred across central Pennsylvania from 1978 to 1990, only 22% of the plots were defoliated severely for more than one year. Net change in basal area/acre from 1978 to 1990 (including both accretion and ingrowth) ranged from +70 to -92% depending on defoliation severity and frequency. Oak species were defoliated disproportionately and had higher mortality rates than non-oak species. Eighty-eight percent of ingrowth trees were of commercial hardwood species (3.3% oak), 4.3% were of commercial softwoods, and 7.1% were of noncommercial species. Regeneration surveys conducted in 1989 and 1992 showed that 77 and 65%, respectively, of the regeneration plots within stands with severe mortality (> 30% basal area/acre) are adequately stocked with commercial hardwood species; 16 and 25% of the regeneration plots in 1989 and 1992, respectively, were fully stocked with oak species. As of 1990, 77.6% of the plots contained fully stocked or overstocked overstories despite two waves of gypsy moth infestation and resultant mortality. As of 1990, residual stands still contain a viable oak component (1990 ave. = 58% basal area/acre in oak), though ingrowth and advanced regeneration data indicate that future stands may have more red maple, birch, and black gum stems, and thus be better able to withstand future gypsy moth infestations.
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Feicht, David L.; Fosbroke, Sandra L. C.; Twery, Mark J. 1993. Forest stand conditions after 13 years of gypsy moth infestation. In: Gillespie, Andrew R.; Parker, George R.; Pope, Phillip E.; Rink, George: eds. Proceedings of the 9th Central Hardwood Forest Conference; Gen. Tech. Rep. NC-161. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station: 130-144