Survival of Prolonged Burial by Subalpine Forest Understory Plants

Abstract

The capacity of forest understory plants for surviving burial was examined using plants buried by a 12to 18-cm layer of volcanic tephra in May 1980 in an old-growth subalpine forest NE of Mount St. Helens, Washington. Plant density and cover were measured in 1983 on 50 1-M2 plots from which tephra had been removed in September 1982; these plants had been buried for almost 3 growing seasons. Results were compared with the same plots before excavation, with 50 plots cleared of tephra in September 1980, and with 100 plots on undisturbed tephra. Before excavation in 1982 there were 22 shoots/M2 in the tephra, mostly Erythronium montanum and Vaccinium spp. Few reached the surface and most were still buried 8to 12-cm deep. Compared to 1st year vegetation in plots cleared 2 years earlier, excavation in 1982 produced equal shrub density, but only 21 % of the shrub cover, 55 % of the herbaceous plant density with only 13% of the cover, and 18% of the bryophyte cover. All conifer seedlings had died. Although plants buried until 1982 had little potential to grow out of the deposit, they survived prolonged burial.