PARENT SESSION
Oral Session #6: Disturbance Ecology of Forests: Fire, Patterns. Presiding: R. DeFries.
Monday, August 6, 2001. 8:00 AM to 12:00 PM. Hall of Ideas F.

Interactions between fire and wind disturbances in a subalpine forest in northwestern Colorado.

Kulakowski, Dominik¹, Veblen, Thomas¹, ¹

ABSTRACT- In 1997, a major windstorm blew down over 10,000 hectares of subalpine forest in northwestern Colorado. We conducted a study of how the prior disturbance history, topography, and forest cover type affected forest susceptibility to the 1997 blowdown. Our central question was how does fire history, across the landscape, determine subsequent susceptibility to damage from a windstorm. We combined dendrochronological techniques with a geographic information system (GIS) to examine the relationship between the effects of the blowdown and the spatial heterogeneity of the vegetation, much of which is determined by fire history. We reconstructed the spatial and temporal fire history in a c. 4,400 ha area by first identifying distinct patches in the landscape on aerial photographs, and then in the field determined the disturbance history of each patch by dating fire scars, ages of post-fire cohorts, and releases of remnant trees. We found topographic position, fire history, and species cover type all to be important in determining stand susceptibility to wind damage. Stands at higher elevations, on east-facing slopes, and those closer to ridges were more affected by the windstorm than stands at lower elevations, on south-, west-, and north- facing slopes, and those further from ridges. Stands more recently affected by stand-initiating fires were less affected than old-growth stands. Populous tremuloides stands were less affected than stands of the conifer cover types. This study shows that the ecological effects of even a very high severity windstorm are mediated by the legacies of prior disturbance by fire.

KEY WORDS: wind disturbance, fire, GIS, Colorado