Response of forest understory vegetation to a major ice storm. J. Torrey Bot. Soc. 131:45-52. 2004.—In January of 1998, Ottawa, Ontario was hit with a major ice storm. Detailed pre-storm vegetation data had been collected in 1997 in 164 forest interior sampling plots across a 3,000 km? region. These data included information on shrubs/saplings, woody seeds and seedlings, herbaceous seeds and ground cover, und canopy cover, For the four growing seusons following the ice storm (1998-2001), we resampled the same 164 plots. In addition, in 1998 we estimated an ice storm damage index for each plot, and the volume of downed coarse woody debris due to the ice storm in each plot. The objectives of this paper were to examine changes in shrubs/saplings and ground vegelation in response to ¡ce storm damage over the four-year period following the storm. Contrary to our initial expectations, we found that woody seedlings showed a large decrease in density immediately following the storm (1998). Woody seedling density recuvered to pre-storm levels by 2001. We hypothesize that the decrease in woody seedling density resulted from reduced seedling germination due to lower tight availability on the forest floor, which resulted from the large amount of woody debris created by the storm. We also found that shrub/supling counts showed a large increase in 1999, most likely due to increased light to the understory, due to opening af the upper canopy. Herbaceous cover increased from 1998 to 2000, but returned to pre-storm levels the following year (2001). The between-plot variation in these under- story changes was positively correlated to plot damage from the ice storm, indicating that they resulted from the storm. Overall, it appears that the forest understory plant structure is rapidly returning to pre-ice storm conditions.

disturbance, forest ecology, ice storm, seed germination, seedling growth, shrubs, saplings, seed bank, forest structure, glaze storm, forest canopy.