Wood Dynamics Along the Terrestrial-aquatic Boundary in Northeastern Forests: The 1998 Ice Storm
Conducted by former post-doctoral associate Andrew A. Millward)
The 1998 ice storm was a large-extent ecological disturbance that severely affected eastern Adirondack forests. Ice damage produced widespread breakage of limbs and trunks in susceptible trees. Although ice storms are regularly occurring disturbances within northeastern North American forests, the magnitude and extent of the 1998 storm exceeded "typical" ice storms observed within the past 100 years. While plot and stand-scale ecological impacts of prior ice storms had received attention insofar as tree species vulnerability, stand age susceptibility, and microhabitat alterations, larger-extent damage patterns had not been previously evaluated. To do this, we employed the normalized difference vegetation index (NDVI) to assess forest vigor and canopy density in atmospherically corrected Landsat Thematic Mapper (TM) satellite images collected prior to and following the 1998 ice storm. We compared forest condition prior to the ice storm (1990 NDVI data) with forest condition observed in the post-storm image (1998 NDVI data). Forest damage was separated from natural variations in canopy reflectance by employing a generalized linear model that incorporated in situ measurements.
We also investigated the forest damage gradient in the riparian zone of 13 stream segments of varying size and 13 lakes. Large streams (fourth and fifth order), occurring in forests that received modest ice damage exhibited significantly more damage in the riparian zone within 25 m of the water than in adjacent forest sections. In similar moderately damaged forests, lake shorelines were significantly more damaged than interior forests. Analysis of transitions in damage intensity revealed that canopy disturbance followed a decreasing trend (up to 3.5 times less) with movement inland from the terrestrial-aquatic interface. The observed predisposition of forest to disturbance along this ecosystem interface emphasizes the role of the physical landscape in concentrating the movement of wood from the forest canopy to locations proximate to water bodies, thus reinforcing findings that ice storms are drivers of ecological processes that are spatially concentrated.
This project was funded by the Fulbright Fellowship Program and Hydro-One.
For further information:
Millward, A. A. and C. E. Kraft. 2004. Physical influences of landscape on a large-extent ecological disturbance: the northeastern North American ice storm of 1998. Landscape Ecology 19:99-111.[Link to Full article]
Millward, A. A., D.R. Warren, and C.E. Kraft. 2010. Ice-storm damage greater along the terrestrial-aquatic interface in forested landscapes. Ecosystems 13:249-260. [Link to Full article]