fire – climate relations in the western sierra nevada tom swetnam & chris baisan

Fire – Climate Relations in the Western Sierra Nevada

Tom Swetnam & Chris Baisan

Colony Mill, Giant Forest

Tree sampled for fire history in 1992Open pine stand

Giant Forest plots

Vegetation, species composition plot data:

Compare pre-settlement compositionestimates with current stand composition.

Relate pre (and post) settlement compositionwith fire regime characteristics among and betweenplots, sites, and transects.

High variability in forest composition between plots

Estimates of b.a. increase from pre-settlement conditionvaried from 0 to 100%. Average increase ~50%.

Giant sequoia fire record in the Circle Meadow areanow extended back prior to ~600BC with some replication.

CEMO (0.15%)

CADE (42.46%)

PIPO (22.69%)PSME (2.48%)

QUCH (12.38%)QUKE (19.84%)

HEL Post83m2/ha

CEMO (0.25%)CADE (15.32%)

PIPO (27.77%)

PSME (2.25%)QUCH (20.90%)

QUKE (33.50%)

HEL Pre49.1m2/ha

Helispot fire history site

Elevation 1350m MFI ~6yrs

Plot species composition

-1600 -1400 -1200 -1000 -800 -600 -400 -200 0 200 400

CCW 01

CCW 02

CCW 03

CCW 04

CCW 05

LIN 01

CM N 07

CM C 08

CM C 03

G ia nt Fo re st fire -sc a rre d tre e s

1

3

4

1. East Cascades, 2 watersheds, 723 trees, Everett et al. 1999, For. Ecol. & Manage., In press.

2. Blue Mountains, 4 watersheds, 628 trees, Heyerdahl 1998 PhD diss., Univ. Wash.

3. West Slope Sierra Nevada, 4 elevational transects, 49 sites, 446 trees, Swetnam & Baisan, In Press.

4. Southwestern US, 63 sites, 1,215 trees, Swetnam and Baisan 1996, USFS RM-GTR-286:11-32.

2

Four Fire-Scar Networks in Western U.S

Paleo-Fire History Databases – in construction

A. L. Westerling, T. J. Brown, A. Gershunov, D. R. Cayan, and M. D. Dettinger. Long lead statistical forecasts of area burned in western U.S. wildfires by ecosystem province. International Journal of Wildland Fire 11:257-266. 2002

Year

1860 1880 1900 1920 1940 1960 1980-2

0

2

4

6

1700 1720 1740 1760 1780 1800 1820 1840

Sta

ndar

d D

evia

tion

Uni

ts

-2

0

2

4

6 12.3

8.2Observed AreaBurned

Statistical Reconstructionof Area Burned

Fire-Scar Reconstructionof Area Burned

Composite fire scar chronologies from 10 forest stands

In the Jemez Mountains, New Mexico

Fire-scar chronology from Santa Catalina Mountains, Arizona

Fire-scar chronology from Gila Wilderness, in Southwestern New Mexico.

Swetnam and Baisan. In press. Fire and climate history in the Sierra Nevada, California and Southwestern US, Veblen et al., Fire and Climate in the Western Americas, Springer-Verlag, Ecol. Studies Series.

Fire-scar chronology from Sierra San Pedro Martir

from Stephens, Skinner and Gill, in review.

Crown King, AZ August 19, 2002; Joel McMillan

Dead and dying trees from a combination of drought stress and bark beetle attack. Area affected is now > 500,000 acres.

This may become one the largest bark beetle outbreaks in recorded history in North America.Data from USDA FS Forest Health Protection, Arizona Zone, Entomology & Pathology group.