COLONIZATION DYNAMICS OF 4 EXOTIC PLANTS IN A NORTHERN PIEDMONT NATURAL AREA

Frequency and density of four invasive non-native plants (Lonicera japonica [L.] Thunb., Ampelopsis brevipedunculata [Maxim.] Trautv., Celastrus orbiculatus Thunb. and Rosa multi-flora [L.] Thunb.) were measured in the Pennypack Wilderness, a 324 ha natural preserve located in a southeastern Pennsylvania suburban landscape. Stem frequency and density of each species were measured during 1988 and 1989 in 163 plots of 20 m2 each located randomly and distributed proportionally among the 10 successional plant communities comprising the preserve. Lonicera japonica was the most frequently encountered and densely growing plant; frequency and density of the other three species appeared to be related to autecological characteristics of the species. Analysis of colonization and density patterns revealed that mature forest generally supported the fewest and least dense colonies, a result of complete shading and limited colonization sites. Frequency and density were also lower in successional plant communities comprising a Mixed Oak forest sere than they were in communities comprising a Mixed Mesophytic forest sere, probably a result of edaphic characteristics or vagaries of the location of introduction.