Recovery of productivity and species diversity in Tussock tundra followingdisturbance

Tundra ecosystems appear to recover slowly from disturbnnce, but little lon g-term data concerning plant diversity has been available. We examined reco very of tundra vegetation in Alaska, U.S.A., 23 yr after fire and 24 yr aft er bulldozing. Primary productivity, depth of thaw, and vascular giant dive rsity were compared between disturbed and undisturbed tundra to determine w hether recovery was complete. Productivity, species richness, and diversity did not differ between burned and unburned plots. Depth of thaw, however, remained greater in burned relative to unburned plots. In contrast, depth o f thaw was the only characteristic that did not differ between bulldozed an d control plots. Productivity and species richness were greater in bulldoze d plots, but diversity was less than control plots. The differences between the two disturbances suggest that, ultimately, recovery depends more on th e impact of disturbance on vegetation than changes in the abiotic environme nt. Vegetative propagules persisted in the soil after fire, but not bulldoz ing. Therefore, recolonization after fire included plants from the seed ban k and vegetative propagules. Vegetation on bladed plots was dominated only by seed bank species. Thus, more than two decades after disturbance, recove ry of tundra vegetation appeared to be a function of the nature of the dist urbance.