Two Ramp Taxa, Allium tricoccum and A. burdickii, Differ in Abiotic Habitat Characteristics and Floristic Associates in Pennsylvania

Abstract

The name ramp or wild leek refers to two taxa: Allium tricoccum and A. burdickii. The latter, named narrow-leaf ramp, has historically been recognized as a variety but recently as a distinct species. Habitat differences between these species have been reported, although distribution of A. burdickii in eastern North America is unresolved. A better understanding of A. burdickii habitat will aid population discovery and conservation as A. burdickii is of conservation concern in parts of the United States. Eight populations, four for each species, were identified in southwestern Pennsylvania. The associated flora, soil fertility and moisture, and site characteristics (e.g., topography) were documented. A. tricoccum was associated with northern aspects and higher soil moisture content throughout the growing season whereas A. burdickii was found on a variety of aspects. Soil pH and nutrient content were greater at A. burdickii sites than A. tricoccum sites and suggest the former may rely more heavily on base nutrients such as calcium. The most common overstory tree associate was sugar maple (Acer saccharum) for both species but understory flora differed. Wet-mesic preferring species, including blue cohosh (Caulophyllum thalictroides) and wood nettle (Laportea canadensis), were associated with A. tricoccum, whereas dry-mesic species, including mayapple (Podophyllum peltatum) and false Solomon's seal (Maianthemum racemosum), were associated with A. burdickii. Results are consistent with observations that these species may differ in mesoscale habitat conditions due to topographic position and its influence on soil moisture and fertility.