Initial Floristics in Lodgepole Pine (Pinus contorta) Forests Following the 1988 Yellowstone Fires

Abstract

The Yellowstone fires of 1988 produced a mosaic of Pinus contorta stands subjected to fire of varying severities. In August, 1989, we inventoried density of vascular plants in paired plots at seven burned stands. One plot was in a severe canopy bum; the paired plot was in an adjacent area that burned at moderate severity. Density of vascular plants was consistently higher in moderate than in severe burn plots. At all sites, floristic composition largely reflected the species present before the fire. Two-thirds of the individuals present in the first postfire season were from vegetative regrowth of plants that survived the fire; of the remaining third, most were P. contorta seedlings. Fire severity had a strong influence on seedling density; at all sites, P. contorta seedling density was higher in the plot classified as a moderate bum. P. contorta seedling density was not related to that of potential competitors. Within sites, the key variable explaining differences between moderate and severe plots is probably loss of seeds consumed or killed by severe canopy fires; differences among sites are likely a consequence of availability of seeds at the time of the fire, a function of the proportion of serotinous trees in the stand.