Plant form, developmental plasticity, and survival following burial by volcanic tephra

Abstract

The morphological responses of 28 shrub and 109 herbaceous species buried by 5–20 cm of tephra (volcanic aerial ejecta) from Mount St. Helens were examined after 1 year of burial. All shrub species produced adventitious roots in the tephra but the extent of roots varied greatly; three shrub species produced extensive rhizomes in the tephra. Most herbaceous species moved perennating buds into the tephra. Upward movement was accomplished in many ways, including upward growth of normally long rhizomes, accelerated elongation of normally short rhizomes, and development of perennating buds on aerial shoots that penetrated the tephra. Nineteen herbaceous species failed to move their perennating buds into the tephra; many of these are forest-dwelling members of the Liliaceae. Herbaceous plants representing a wide range of morphological types successfully penetrated tephra deeper than 12 cm; other species representing the same morphological types failed to penetrate deep deposits. A range of plasticity in several attributes of growth form appeared following burial.