Plant succession in areas of scorched and blown-down forest after the 1980 eruption of Mount St. Helens, Washington

Patterns of plant succession were studied in areas of scorched and blown-downforest resulting from the 1980 eruption of Mount St. Helens, Washington. Changes inplant abundance were observed for a 7 yr period in permanent sample plotsrepresenting four types of post-disturbance habitats, or site types. A largeproportion of the post-eruption vegetation derived from plants that persisted throughdisturbance. Survival and subsequent recovery of understory species were greatest inforests that supported a snowpack at the time of eruption. Gradually, however,species composition on previously forested plots converged toward that of formerlyclearcut sites, due to widespread recruitment and clonal expansion of early seralforks.

Keywords: Detrended correspondence analysis, Life-form development, Plantrecovery, Species diversity, Tephra, Volcanic disturbance.