Overstory and Herbaceous Layer of a Riparian Savanna in Northwestern Pennsylvania


Charles E. Williams

Additional Authors:

William J. Moriarty and gary L. Walters


March – 1999


Herbaceous, Riparian, Sacanna, Pennsylvania, Populus tremuloids, Prunus serotina, Amelanchier arborea

Vegetation species composition and richness was examined in a riparian savanna in the nonglaciated Allegheny Plateau of northwestern Pennsylvania. Microtopography within the savanna consisted of numerous small, dry ridges alternating with saturated depressions. The sparse (tree density = 54.7 stems/ ha; basal area = 7.1 m2/ha; overstory cover = 31.9%) savanna overstory (trees ≥ 10.0 cm dbh) was composed of six species with Prunus serotina Ehrh., Populus tremuloides Michx., and Amelanchier arborea (Michx. f) Fern. of greatest importance. Ten woody plant and 50 herb species were recorded from the herbaceous layer (all vascular plants ≤ 1 m in height) of the savanna with wetland species dominant in wet depressions and upland species dominant on dry ridges. Results of this study indicate that riparian savannas of the nonglaciated Allegheny Plateau can support a relatively rich flora consisting of an unusual mix of upland and wetland species, a marked contrast to the low species richness typical of upland savannas of the region.