last update December 05, 2000
Abstract
The 18 May 1980 eruption of Mount St. Helens resulted in the burial of relatively well developed soild under variable depths of sterile tephra and ash. During summer 1982, we examined a series of sites and estimated the number of spores of Endogonaceae that had been transported from the burial soil to the new ground surface by either abiotic or biotic vectors. There was no difference between spore counts of Endogone spp. or Glomus spp. in the burried soils of forests and clear-cuts; spores were rare in the tephra at any site. In areas featuring <= (less than or equal to) 50 cm of tephra, spores were transported to the surface by gophers (in previous forest and clear-cut habitats). In the Pumice Plain, and area devoid of gophers and ants, erosion exposed spores to the surface. We found no evidence to suggest that endogonaceous fungi grow back up root systems from buried horizons. We hypothesize that small-scale perturbations (erosion, gopher and ant mounds) following the major volcanic disturbance may drive succession by exposing buried mycorrhizal and decomposer fungi.