Reestablishment of Endogonaceae on Mount St. Helens: Survival of Residuals

Abstract

The May 18, 1980 eruption of Mount St. Helens resulted in the burial of relatively well developed soils under variable depths of sterile tephra and ash. During summer 1982, a series of sites was examined, and the numbers of spores of Endogonaceae that had been transported from the buried soil to the new ground surface by either abiotic or biotic vectors were estimated. There was no difference between spore counts of Endogone spp. or Glomus spp. in the buried soils of forests and clear-cuts; spores were rare in the tephra at any site. In areas featuring .ltoreq. 50 cm of tephra, spores were transported to the surface by gophers [Thomomys talpoides] (in previous clear-cut areas) and by ants (in previous forest and clear-cut habitats). In the Pumice Plain, an area devoid of gophers and ants, erosion exposed spores to the surface. There was no evidence to suggest that endogonaceous fungi grow back up root systems from buried horizons. Small-scale perturbations (erosion, gopher and ant mounds) following the major volcanic disturbance may drive succession by exposing buried mycorrhizal and decomposer fungi.