Fire Ecology Overview

Scott StephensDepartment of Environmental Science,

Policy, and ManagementUniversity of California, Berkeleysstephens@berkeley.edu

Outline• Present information from California’s forests regarding their fire regimes and conditions– Begin in coastal areas and move eastward

• What types of fire regimes are encountered?• Examples of resilient forests

– Resilient forests not only accommodate gradual changes related to climate but return toward a prior condition after disturbance either naturally or with management assistance

– Forests that can maintain the ability to regenerate, evolve, and provide ecosystem services to current and future conditions are desirable

• Are there some general ideas that apply to the creation of resilient forests?

Coastal California

• Native American ignitions were once very important in this area – Native Americans burned for a diverse set of objectives. Tending the Wild, Kat Anderson, UC Press, 2005.

• Lightning ignitions are rare in this region because of limited topography and when lightning occurs, mostly wet

Coast Redwood, Once mostly frequent fire return intervals

Oak woodlands, mixed evergreen forests. Once frequent fire return intervals

Coastal Douglas-fir. Infrequent stand replacement and mixed severity fires, underburning by Native Americans

Coastal Forests Summary

• Native American fires reduced– Once important in coast redwood, oak woodlands, mixed evergreen forests

– We have removed an important ecological process that occurred for thousands of years

– Fire hazards are not a big issue in these forests– Ecosystem health is an issue

• Low regeneration of some species, nutrient cycling missing, introduced diseases (SOD)

Interior Forests

• Coastal, Southern California, Klamath, Southern Cascades, and Sierra Nevada mountains

• West-side: ponderosa pine, dry Douglas-fir, mixed conifer, white and red fir, lodgepole pine, alpine pines

Interior Forests• White and red fir, steep Douglas-fir, some mixed conifer– Many of these areas are more mesic, found in northern California

– Longer fire return intervals, mostly low but some mixed severity fire regimes

– Topography important influence in many areas, not all• (Beaty and Taylor 2001, 2008, North et al. 2009, Scholl and Taylor 2010)

– Fire regimes of riparian areas connected to uplands in most cases (Skinner 2003, Van de Water and North 2010)

• Alpine pines– White bark, limber, foxtail

• Lightning ignitions occur, low fuel continuity

Ponderosa pine, Klamath Mountains

Rugged topography common Topography influences past fire regimes (Skinner and Taylor)

Ponderosa Pine in the Southern Cascades

The Pinery east of Chico, CA.

Burned 4 times in 20th century

Very resilient ecosystem

Mixed Conifer, Giant Sequoia-Mixed Conifer, Sierra Nevada

Most of these sites are very productive. Removal of fire and past harvests have created high fire hazards and low amounts of shade intolerant regeneration

Forest Inventory Data from 1911, West Yosemite National Park

Collins et al., Ecosphere, in review

Frequ

ency (nu

mbe

r of lo

ts)

Collins et al., Ecosphere, in review

Collins et al. 2011 Ecosphere

1911 Forest Structure Summary

Frequency (Number of Lots, 28 total)

Wildland Fire Use, Illilouette Creek basin in Yosemite National Park

Fires self limiting, < 9 years between fires they don’t overlap except extreme weather

Low, moderate, high severity fire proportions stable over last 30 years

High severity fire 15%, most patches < 4 ha (Collins et al. 09, Collins and Stephens 10)

Ponderosa Pine, Mixed Conifer Forest Summary

• Frequent, low-moderate intensity fires once common, some mixed severity

• Most forests of this type have high fuel loads and high stand densities– Shade tolerant species dominate understory

• Higher site quality, more change

• Restoration needed– Fire and Fire surrogates and wildland fire use

• Moderate severity fire (fire use and Rx fire) produced forest structure similar to that in 1911, resilient structure

• High amounts of spatial heterogeneity desirable

Other West-side Forests in Need of Management

• Conifer plantations– Products of reforesting past wildfires– Products of even-aged management– Most federal plantations receive few cultural treatments after establishment, changing

– Most private plantations receive cultural treatments to increase tree growth

– Many of these have fire hazard problems

Prescribed Fire in Spring after Whole Tree Removal

Red Turpentine and Western Pine Beetle Attacked Stressed Trees

High bole scorch and overstory damage, red turpentine beetle arrives, western bark beetle can follow

Plantations Summary• Great need for creative work to break up continuity of crown and surface fuels

• Whole tree removal very useful– Especially where thinned trees have value

• Prescribed burning is possible– Scorch of lower crowns, raise height to live crown base

– Bark beetle interactions – Some trees will be killed, maybe good

• Plantations are too homogeneous

Interior Forests

• Southern California, Klamath, Southern Cascades, eastern Sierra Nevada– Jeffrey pine, Ponderosa pine, mixed conifer mostly frequent, low-moderate intensity fire regimes, some mixed severity

– Many of these forest types were clear-cut or partially cut in the late 1800’s and early 1900’s• Especially accessible sites

– Forest density increased, many areas once pine dominated but classified today as mixed conifer forests?

Sierra San Pedro Martir Mountains

Northern Baja CaliforniaMediterranean climate (more summer precipitation than most of CA.)

Annual precipitation averages 22 inFire suppression begins in 1970Granitic parent material commonArea has been grazed by livestockNo harvesting

July 2003 Wildfire

Burned at the end of a severe 4 year drought, same as in the Southern California mountains

Wildfire Impacts• Approximately 20% of trees killed (Stephens et al. 2008)

• Fire was very patchy –directly linked to heterogeneity of forest structure and fuels (Fry and Stephens 2010)

• produces fire with diverse effects• continues high spatial heterogeneity

–Bark beetles killed a few trees–Very resilient forest

Summary of Resilient Forests

High amount of spatial variability desired, probably was the pre-historic landscape– can live with some areas with high fuel hazards

Contrast: Large continues forested areas with high horizontal continuity and fire hazards– very susceptible to severe disturbances

Management methods that create homogeneity should be avoided

Should not seek to create average stand conditions replicated over large spatial scales

Conclusion• California’s forests are very diverse

– Many once experienced frequent, low-moderate intensity fire regimes, some mixed severity

• Removal of fire has reduced spatial heterogeneity, need to modify this

• Where possible, increased use of Wildland fire use for resource objectives desirable– There is risk of such a strategy but this may be the best method to get fire back into California’s forests even at modest spatial scales

• Increased use of fire and fire surrogates – Including commercial harvests is possible but must be an explicit objective

SummaryNathaniel Kenney wrote a paper in 1956 in National GeographicOur green treasury, the national forests

Said fire researchers needed to let their imaginations soar to find solutions to the current wildfire problem

55 years later he was right but solution is getting appropriate fire or fire surrogates back into fire dependent ecosystems

Critical for resilient forests and changing climates