Short-term understory plant community responses to timber-harvesting intensity on non-industrial private forestlands in Pennsylvania Todd S. Fredericksen 1,a,* , Brad D. Ross b , Wayne Hoffman c , Michael L. Morrison d , Jan Beyea e , Bradley N. Johnson f , Michael B. Lester g , Eric Ross h a Top Bol #5053, PO Box 52-0777, Miami, FL 33152-0777, USA b National Audubon Society, 204 Ferguson Building, The Pennsylvania State University, University Park, PA, 16802, USA c National Audubon Society, 115 Indian Mound Trail, Tavernier, FL 44070, USA d Department of Biological Sciences, California State University, Sacramento, CA 95819, USA e Consulting in the Public Interest, 53 Clinton Street, Lambertville, NJ 08530, USA f The Proctor & Gamble Company, 6100 Center Hill Avenue, Cincinnati, OH 45224, USA g The Procter & Gamble Company, P.O. Box 32, Mehoopany, PA 18629-0032, USA h Department of Forestry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA Received 10 March 1998; accepted 21 July 1998 Abstract Understanding harvesting impacts on non-industrial private forestlands is important, since they represent 75% of all commercial forestlands in the State of Pennsylvania, as well as a large percentage of most of the eastern United States. This study measured species composition, richness, and diversity of herb- and shrub-layer plant communities on a total of 40 non- industrial private forest stands in northeastern Pennsylvania. These northern hardwood and oak±hickory stands had been recently harvested at different intensities. Remaining basal area was used as an indicator of harvest intensity. Species richness and diversity were not signi®cantly related to basal area for summer or vernal herb understory plant communities for either forest type, although there was some evidence of a weak negative relationship between plant species richness and remaining basal area on more intensively harvested northern hardwood stands. Summer plant-species richness and diversity were related to percent litter cover and percent slope on northern hardwood stands, and percent Vaccinium cover and percent slope on oak± hickory stands. Ground- and shrub-layer cover signi®cantly increased with increasing harvest intensity. Species composition of vernal herb communities did not vary in stands with differing amounts of basal area. Species composition of summer forest- ¯oor communities differed with amount of basal area remaining, but only for northern hardwood stands. Shade-intolerant ruderal species dominated northern hardwood stands with low basal area, while more shade-tolerant plants dominated northern hardwood stands with high basal area. Summer plant understories of northern hardwood stands were generally dominated by fern and/or Rubus spp. (blackberry and raspberry), while oak±hickory stands were dominated by Vaccinium (blueberry) species. Litter cover, Vaccinium cover, fern cover, total ground cover, and forest type were signi®cant variables related to species composition of vernal herb communities. Based on these results, forest landowners in this region should not expect signi®cant short-term changes in vernal herbaceous or summer understory plant richness or diversity on their lands, regardless of the intensity of logging. However, short-term changes in vegetation structure (increased growth of forest-¯oor and shrub Forest Ecology and Management 116 (1999) 129±139 *Corresponding author. E-mail: nelltodd@bibosi.scz.entelnet.bo 1 Current address: Tropical Research and Development Inc., Proyecto BOLFOR, Santa Cruz, Bolivia. 0378-1127/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved. PII: S0378-1127(98)00452-6