Woody species composition of disturbed forests in intermittent stream bottomlands of southern Indiana

JENKINS, M. A. (Twin Creeks Natural Resources Center, Great Smoky Mountains National Park, Gatlinburg, TN 37738) AND G. R. PARKER (Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907). Woody species composition of disturbed forests in intermittent stream bottomlands of southern Indiana. J. Torrey Bot. Soc. 128: 165-175.-Between 1993 and 1995 we sampled understory and overstory woody vegetation on 84 plots in Platanus/Asarum Wet-Mesic Bottomland forests to determine how these forests have responded to human disturbance. Four different types of disturbed stands were sampled (abandoned agricultural areas, clearcuts, group selections, and single-tree selections), and 80-100 year-old reference stands were sampled for comparison. Overstory vegetation differed in composition among these 5 stand types with abandoned agriculture, clearcut, and group selection plots exhibiting compositions very different from single-tree selection and reference plots. This was largely due to shifts in dominance by Acer saccharum and Liriodendron tulipifera across the five stand types. Although abandoned agricultural areas experienced more severe site disturbance from years of cultivation, they were similar in composition to clearcuts and group-selection openings. The mean species richness of abandoned agriculture, clearcut, and group-selection plots was generally greater than that of single-tree selection and reference plots. Abandoned agricultural areas and clearcuts had greater overstory species richness (summed across all plots), suggesting that larger canopy openings have allowed more shade-intolerant species to establish. Total species richness was greatest on abandoned agriculture plots due to an influx of drysite, disturbance, and exotic species. However, these species did not tend to dominate sites. The dominance of A. saccharum in single-tree selection openings has led to the exclusion of other species, resulting in greatly reduced overstory species richness and diversity.