LONG-TERM RECOVERY OF VEGETATION ON 2 EXPERIMENTAL CRUDE-OIL SPILLS IN INTERIOR ALASKA BLACK SPRUCE TAIGA

Vegetation was sampled on two black spruce taiga sites in interior Ala ska, 15 and 20 years after crude oil was experimentally applied as low -volume sprays or high-volume point spills. Low volume spray spills th at uniformly covered the ground caused initial damage to vegetation, b ut after 20 years recovery of the understory vegetation was almost com plete, with dramatic recovery and expansion of fruticose lichens. High -volume point spills created small areas of surface oil saturation wit h dead vegetation and little sign of recovery but spread out mostly be lowground with little or no apparent effect on the shallowly rooted ve getation above even after 15-20 years. Because winter point spills cre ated a much greater area of surface oil, their effects were more damag ing. After 15 years on the saturated surface oiled areas, only Eriopho rum vaginatum tussocks survive and grow. At both sites with surface oi l, black spruce mortality was high, with no evidence of long-term reco very and with continuing chronic effects after 15 years. However, from a long-term perspective the black spruce taiga ecosystem appears to b e able to recover from low volume spray spills and to retain large amo unts of crude-oil from high-volume point spills belowground with minim al damage to the vegetation. Because of the permafrost, removal of cru de oil from this ecosystem by soil excavation is undesirable. In situ acceleration of oil breakdown using fertilizers and bacteria is a poss ible option; seeding or planting of E. vaginatum on surface-oiled area s may also provide some cover and belowground biomass.