REGIONALIZTION OF FIRE REGIMES ACROSS THE ROCKY MOUNTAINS, USA

Fire is one of the most important natural disturbances in the coniferous forests of the Rocky Mountains. However, it is unclear how differences in climatological conditions between the northern Rocky Mountains (NRM) and southern Rocky Mountains (SRM) affect regional fire regimes. A proposed climatic boundary between 40^o - 45^o N latitude separates the NRM and SRM. To determine whether the fire regime across this climatic boundary was more similar to the NRM or SRM during the Holocene, a 12539-year-old sediment core from Long Lake, Wyoming, located in the central Rocky Mountains (CRM), was analyzed for charcoal and pollen. These data were then compared to charcoal records from the CRM, NRM and SRM. During the Younger Dryas chronozone (12539-11800 cal yr BP), the fire regime was characterized as frequent at Long Lake. The early Holocene (11800-9400 cal yr BP) and middle Holocene (9400-4000 cal yr BP) fire regime was characterized as infrequent. A brief interval from 4000-3000 cal yr BP, termed the Populus period, had a frequent fire regime, which remained frequent through the late Holocene (3100 cal yr BP - present) at Long Lake. In comparison to sites from the NRM and SRM, the fire regime at Long Lake was most similar to the SRM during the past 12539 cal yr BP. These results suggest the disturbance regime in the CRM has a greater affinity with those of the SRM.