Thursday, 20 November 2003: 1:30 PM
Fire history of Lava Cast Forest, Central Oregon
We examine a 400-year tree-ring record of fire history to determine its spatial and temporal dynamics across a naturally fragmented landscape in central Oregon. Our analysis compares a suite of spatial and environmental factors related to fire history determined from 88 partial cross-sections from live and dead trees located on forest isolates (kipuka) and in the surrounding contiguous forest. The tree ring record yielded 352 scars between 1170-2001 AD with a 13.3 year mean fire return interval (MFRI) between 1600-2000. MFRI increased from 7.9 years (1600-1799), to 16.0 years (1800s) and 41.5 years (1800-2001) and is consistent with MFRIs reported elsewhere in western North America including the sharp decrease in fire frequency beginning in the late 1800s. Our spatial analysis shows that although MFRIs increased from the surrounding forests to the kipuka, the differences are not statistically significant for any of the time periods tested. Occurrence of fire is correlated to several spatial and environmental factors including the relative isolation, slope, aspect, and elevation differences. Forest fragmentation irrespective of other environmental factors serves an important function in governing the behavior of fire and in the development of a complex mosaic of forest types and stand structures.