HR: 17:00h
AN: B14C-04 INVITED    [Abstracts]
TI: Climate drivers of fire extent and severity in US Rocky Mountains
AU: * Morgan, P
EM: pmorgan@uidaho.edu
AF: University of Idaho, Department of Forest Resources PO Box 441133, Moscow, ID 83844-1133, United States
AU: Heyerdahl, E K
EM: eheyerdahl@fs.fed.us
AF: US Forest Service, Fire Sciences Laboratory 5775 US W Highway 10, Missoula, MT 59808, United States
AU: Holden, Z
EM: zholden@vandals.uidaho.edu
AF: University of Idaho, Department of Forest Resources PO Box 441133, Moscow, ID 83844-1133, United States
AB: Years of extensive forest fires, 1900-2003, in the US Northern Rockies in Idaho and western Montana had warm springs followed by warm, dry summers and positive Pacific Decadal Oscillation (PDO). We identified these years as those exceeding the 90th percentile in annual fire extent derived from an existing fire atlas that includes 5,038 fire polygons recorded from 12,070,086 ha, or 71% of the forested land in Idaho and Montana west of the Continental Divide for 1900-2003. The long mid-20th century period lacking regional-fire years (1935-1987) had generally cool springs, generally negative PDO, a lack of extremely dry summers, and was a period of active fire suppression. In years of extensive fires, the climate drivers did not differ among dry forests, mesic forests and cold forests. Similarly, in the 32 years in which fires occurred on at least 5 of 21 widely dispersed sites sampled for fire scars 1650-1900, spring-summers were significantly warm and summers were significantly warm/dry compared to the 99 years when no fires were recorded at any site. Given projections for warmer springs and continued warm, dry summers, forests of the US Northern Rockies are likely to experience synchronous, widespread fires in the future. We also analyzed burn severity interpreted from a time series of Landsat satellite images (114 fires burned 195,600 ha, 1986-2004, on the 1.4 million-ha Gila National Forest, New Mexico), daily weather and SNOTEL data. Snowpack and precipitation influenced fire extent and severity in upper elevation forests. Fire extent and severity in mid-and low elevation forest types were strongly correlated with fire season (April-July) precipitation variability. Recent cross-continental and cross-regional analyses highlight the importance of climate in driving fire occurrence. Less is known about why, where and when large, severe fires are most likely and the influence of climate, land use, vegetation, fuels management, topography, and other disturbances.
DE: 0429 Climate dynamics (1620)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0468 Natural hazards
DE: 0476 Plant ecology (1851)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting