SUCCESSION FOLLOWING THE CATASTROPHIC ERUPTION OF KSUDACH VOLCANO (KAMCHATKA, 1907)

Ksudach Volcano, southern Kamchatka Peninsula, erupted in 1907 and imp acted over 2000 km(2) of forests with air-fall pumice deposits. We ide ntified three impact zones. In Zone I, deposits deeper than 100 cm des troyed all vegetation. Two early successional stages occur, a lichen-d ominated desert and isolated patches of a pioneer herb stage. Zone II is defined by pumice deposits 30 to 100 cm deep. Deposits of 70 to 100 cm destroyed all vegetation, but left scattered snags. Here primary s uccession dominates recovery, but its rate varies. Isolated trees surv ived in deposits of 30 to 70 cm and primary and secondary successional stages form a complex mosaic termed an intermediate succession. In Zo ne II, the primary stages found in Zone I are joined by a dwarf shrub- herb stage and a secondary birch forest stage. Zone III occurs where t hinner deposits permitted some vegetation to survive in all locations. Secondary succession dominates in deposits of 10 to 30 cm. Trees suff ered damage, but survived deposits of 20 to 30 cm, while other vegetat ion layers were eliminated. Deposits of 10 to 20 cm eliminated mosses and lichens and but only reduced the number of dwarf shrubs and herbs. Deposits of less than 10 cm damaged herb, moss and lichen layers but did not eliminate any species. All sampled vegetation remains in a pre -climax state, having yet to recover fully from earlier eruptions. Rec onstructed vegetation maps for before 1907 and for ca. 1925 are compar ed to the map of vegetation in 1994. Based on degree of soil formation , vegetation recovery and colonization rates at different pumice depth s, and the current vegetation, we estimate that full recovery of the s oil-vegetation system will take more than 2000 years.