Clonal expansion in the deciduous understory shrub, devil's club (Oplopanax horridus; Araliaceae)

Abstract

To examine clonal growth and the ability of devil's club (Oplopanax horridus (Sm.) Torr. & A. Gray ex Miq.) to persist throughout stages of forest succession, we sampled populations in three classes of stand development: clearcuts (1–10 years old), young stands (11–50 years old), and maturing stands (51–200+ years old). We completely excavated and mapped all clonal fragments (systems of ramets connected by decumbent stems) in a plot at each site and determined ramet and clonal fragment age using annual growth rings on stem cross sections. Clonal fragment density and size, ramet density and age, decumbent stem length, annual stem elongation, annual ramet recruitment, lateral meristem formation, and the number of persistent dead ramets were significantly (P < 0.05) related to stand development class. Clonal fragments in clearcut stands were large, predating the year of stand establishment, with many dead, old ramets, but many young stems. Ramet recruitment and lateral meristem formation were highest in clearcut stands, which contributed to replacement of older ramets lost to the disturbance. Clonal fragments in young stands were few and small, consisting of a few ramets and short decumbent stems. In maturing stands, clonal fragments were numerous but consisted of few ramets with extensive decumbent stem connections. No devil's club seedlings were observed in any of the stands sampled. Devil's club populations are maintained by prolific basal stem sprouting following disturbance and continual layering and clonal fragmentation throughout stand development.Key words: age structure, clonal architecture, clonal shrubs, demography, layering, population dynamics.