Beyond boreal forests: Holocene fire history in Alaskan tundra ecosystems
Philip Higuera Montana State Univ. and Univ. of Illinois Melissa Chipman Univ. of Illinois Jennifer Allen National Park Service Scott Rupp Univ. of Alaska Mike Urban, Feng Sheng Hu
Univ. of Illinois Photo: Dale Woitas, AFS, BLM 1 Shrub expansion:
Will tundra area burned increase?
AK Fire Service, BLM
W. Chapman , U of IL: http://arctic.atmos.uiuc.edu/CLIMATESUMMARY/2003 Photo: Dale Woitas, AFS, BLM 2 I. Background Paleo Evidence of Frequent Tundra Fires
Tundra fire frequencies could increase with shrub abundance and climatic drying
Higuera et al., 2009, Ecological Monographs 3 AK Fire History ≈ 90% area burned in boreal forest
> 1.8 million ha burned in tundra
1332 citations: “boreal forest + fire”
139 citations: “tundra + fire”
4 II. Objectives 1. Quantify tundra fire history over the past 6000 years
2. Infer climate-vegetation-fire relationships from pollen and independent paleocliamte records
3. Inform ecosystem model (ALFRESCO) for assessing fire and fuels hazards in tundra under future climate / veg.
5 III. Study Design
Noatak NP graminoid shrub Bering Land Bridge NP graminoid shrub Anaktuvuk River Fire
6 Noatak Study Area
50 km Noatak Study Area
Graminoid Tundra: Shrub Tundra: Cyperaceae , Poaceae, dwarf shrubs Betula, Alnus, Salix 8 IV. Tundra Fire History Age Models age (cal. yr BP) age (cal.
depth (cm) 9 Fire History from Sed. Charcoal
Cair = airborne fallout of charcoal Cls = charcoal on landscape surface Clake = charcoal on lake surface Ccore = charcoal in center of lake Cair = f(d)
Cls = f(d)
Clake = f(Cair, slope wash)
Ccore = f(Clake, redeposition, mixing)
Higuera et al., 2007, Quaternary Science Reviews. Peters and Higuera, 2007 Quaternary Research 10 Peak Identification
Raven 1. Tundra burns
Uchugrak )
-1 Records appropriate
yr for peak identification -2 Recent large fires Poktovik detected CHAR (# CHAR (# cm
Little Isac
age (cal. yr BP) 11 Fire regimes of the last 2000 years
Graminoid (2-0 ka BP): 2. Location matters: Wbl c = 1.94 (1.55-3.34) N = 27 vegetation FRImedian = 135 yr (105-150)
Shrub (2-0 ka BP): Wbl c = 1.58 (1.16-2.75) N = 13
FRImedian = 180 yr (165-375) density OR proportion (x20) density OR
FRI (yr) 12 Fire regimes of the last 2000 years
Graminoid (2-0 ka BP): 2. Location matters: Wbl c = 1.94 (1.55-3.34) N = 27 vegetation FRImedian = 135 yr (105-150) and/or climate
July max Temp.
Shrub (2-0 ka BP): Wbl c = 1.58 (1.16-2.75) N = 13
FRImedian = 180 yr (165-375) Ann. Precip. density OR proportion (x20) density OR
FRI (yr) 13 Temporal Scales of Change ) -1 yr -2
CHAR (# cm Uchugrak Lake fire frequency(fires100yr temporal scale (yr) temporal scale -1 )
age (cal. yr BP) 14 Temporal Scales of Change
Raven fire frequency(fires100yr
Uchugrak Lake temporal scale (yr) temporal scale -1 )
age (cal. yr BP) 15 Millennial-scale synchrony
Raven-Uchugrak: 6.5-0 ka BP
synchrony ) t independence ( hat AB L
t (yr)
16 Millennial-scale synchrony 2. Synchrony suggests climatic controls: Raven-Uchugrak: 6.5-0 ka BP Poktovik-Little Isac: 6.5-0 ka BP Raven-Uchugrak-Little Isac: 6.5-3.0 ka BP ) -1 fire frequency (fires 1000 yr fire frequency
age (cal. yr BP) 17 Brooks Range Relative Moisture accumulation (g cm sand -2 yr -1 )
drier
wetter O (‰V-PDB) 18 δ ) -1 fire frequency (fires 1000 yr
Mann et al. 2002, QSR; Clegg and Hu in review age (cal. yr BP) 18 Climate and vegetation likely interacted 4. Role of vegetation dependent on climate: shrub tundra more flammable in drier climate
+Betula
Little Isac
+Alnus
+ Poaceae PCA axis 2 axis PCA
+Cyperaceae
PCA axis 1 19 V. Conclusions
1. Sediment charcoal reveals that tundra can burn as frequently as boreal forest
2. Synchronous changes and paleorecords suggest climate and possibly vegetation drivers of tundra fire regimes
3. Tundra fire regimes should be sensitive to ongoing environmental change
20 Acknowledgements and Questions Funding: Joint Fire Science Program and the National Park Service.
Field Assistance: Denali National Park fire personnel
Lab Assistance: Triet Vuong and Jennifer Schwarz
Poktovik Lake, 11:30 pm, June 19th