PARENT SESSION
Poster Session #59: Fire Ecology II.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Crownfire history reconstruction of the upper Rio Grande Basin .

Margolis, Ellis^*,1, Swetnam, Thomas¹, Allen, Craig², ¹ University of Arizona, Tucson, AZ² U.S. Geological Survey, Los Alamos, NM

ABSTRACT- Dendroecological techniques were applied to reconstruct crown fire history in mixed conifer and spruce-fir forests in northern New Mexico and southern Colorado. Crown fire dates with annual accuracy and precision were determined using four lines of evidence for each of twelve sites, within a 75,000 square kilometer area. The four lines of evidence were: (1) aspen inner-ring dates, (2) conifer death dates, (3) tree-ring width changes, or other morphological indicators of injury, and (4) fire scars. The annual precision of dating allowed the identification of significant synchrony of crown fires among the 12 sites and regional surface fires previously documented throughout the Southwest. The majority of these synchronous crown and surface fire years coincided with droughts. This suggests that crown fire activity occurred primarily when drought conditions allowed the spread of surface fires from lower elevations into upper elevation mixed conifer and spruce-fir vegetation zones. More than 50% of the crown fires pre-dated large-scale Euro-American settlement in this region. This may suggest that land use practices (such as logging and mining) were not as important in promoting crown fires in these study sites, as compared with other areas in Colorado.

KEY WORDS: crownfire history, dendroecology, populus tremuloides, Rio Grande Basin