Why Woody Biomass? Forest Management Perspective

Malcolm North, USFS Pacific Southwest Research Station, and Dept of Plant Sciences,

U.C. Davis

Fire suppressed forest, northern Sierra Nevada

Forest with a restored fire regime, eastern Sierra

Nevada

Contain the tallest (the coast redwood ‘Hyperion’ @ 378 ft), largest (General Sherman [giant sequoia] @ 55,000 ft3) and possibly oldest (Methuselah [bristlecone pine] >5,000 yrs) trees in the world

Some of the forests are among the most productive in the world

California’s National Forests are growing at the rate of 3.7 billion board feet/year on 9.8 million acres of non-reserve land

N.F. harvest levels are at 8% of growth; 92% accumulates

Many forests are overstocked with small trees that significantly reduce forest resilience to wildfire, pests/pathogens and changing climate conditions

California’s Forests

Most Productive Sierra Nevada Forest Types Are Fire Dependent

Forest Type Fire Return Interval (yrs)

Douglas-fir

Current FRI

≈12-17

≈480

Ponderosa pineCurrent FRI

≈4-10

≈275

Mixed coniferCurrent FRI

≈12-20

≈690

Fir:White

Current FRI

≈30-50

≈850

Historic and Current Forest Conditions and Fire SeverityT

ime P

eri

od

Historic (pre 1870)

Current (after 1970)

Current wildfires burn differently: mostly high-intensity crown fires that kill most trees even the large, old ones.

Unburned, untreated forest quickly increases in density and becomes at-risk to insects,

disease, drought and wildfire

Current Condition of Untreated Fire-

Suppressed Forests: Reduced Ecosystem

Services

1) High stem density: Many ecosystem processes (nutrient cycling, decomposition, etc.) stall.

2) High canopy cover: dramatically reduces variability in microclimate and wildlife habitat, reduces surface snowpack depth and water production.

3) Fuels accumulations: Heavy litter and coarse woody debris homogenizes the forest floor substrate reducing understory plant diversity and cover.

• Increased tree density from fire suppression leads to drought stress

• Mortality in the forest is now primarily driven by drought/beetles

• Climate change is likely to make this a substantial problem: greater annual weather variability, higher evaporative demand, bark beetle populations are kept in check by cold over-wintering temperatures—a condition that is likely to become more rare.

• Thinning and biomass removal substantially reduces competition for scarce soil moisture increasing tree resilience

Forests have higher mortality and are less resilient to climate change

Turkey Creek in the 138,000 acre Hayman Fire aftermath

on the front range of the Rocky Mountains – Denver says $20 million still to be spent to dredge 1 million

cubic yards of sediment from their municipal reservoirs.

Wildfire Expenses: Watershed Damage and Litigation

Legal Expenses:Sierra Pacific Industries settles for $122.5 million for starting the Moonlight Fire (above) when a bulldozer strikes a rock

PG&E pays $29.5 million for starting the Fred’s fire when a pruned tree hits a power line

Is Thinning Necessary or Can Fire Alone Achieve Restoration?

With fire only there are often at least 4 obstacles:

Fire is not surgical3)Litter accumulation can produce hot, long-duration temperatures that can kill large, old trees.

2)

1) Without thinning, small and intermediate size trees can ‘ladder’ surface or ground burns into catastrophic crown fires.

4) Difficult to create gaps where and when you want them

Untreated

Thinned and Prescribe Burned

Fire

DirectionCone Wildfire, N. Calif.

Compelling evidence that mechanical fuels treatments, which reduce specific ladder and surface

fuels, can be highly effective‘Tested’ fuels treatments in the Sierra include Angora, Brown, Sugarloaf, Power, Pittville, Milford, Antelope-Wheeler, Moonlight, American River Complex, Piute, Rich, Grass Valley, Cone, and Calpine

Sugarloaf Fire: Treated (above) and Untreated (below) forest within 200 m.

• Litigation and economics are probably the two leading roadblocks

• One of the perceived conflicts is the association of some sensitive species with forest conditions that have high surface and ladder fuel loads and high canopy cover. How do you provide habitat for these species while reducing fuel loads?

•

Newspaper cover story, northern goshawk and California spotted owl

What’s Holding Up Implementing Fuels Treatments?

Recent science summaries suggest a strategy for implementing fuels reduction while also providing for

wildlife habitat and forest restoration:Use topography as a guide to create variable forest

conditions

Landscape schematic of variable forest conditions produced by management treatments that vary by topographic factors such as slope, aspect, and slope position. Ridgetops have the lowest stem density and highest percentage of pine in contrast to riparian areas. Midslope forest density and composition varies with aspect: density and fir composition increase on more northern aspects and flatter slope angles. Riparian forest provide high canopy cover movement corridors.

Why are Fuels Treatments Stalled? Economics• The large-scale fuels treatments

which are needed will never occur unless most of them can ‘pay for themselves’.

• Thinning merchantable trees, however, rarely affects potential wildfire intensity, and can create the perception and problems associated with ‘getting the cut out’.

• The most effective fuels treatments remove small material—biomass—but without a market, material is left or treatment never occurs.

• A market for biomass could substantially increase the pace and scale of much needed fuels reduction treatments.

Summary:• Research is very consistent that mid-

elevation S.N. forests did not evolve with the current high density of small tree resulting from fire suppression

• Research also suggests removal of small trees (≈ diameter <14”) may benefit ecosystem functions particularly by reducing moisture stress

• Reduction in surface fuel loads have significant positive effects jump starting, stalled ecosystem processes (i.e., understory diversity, decomposition, nutrient cycling)

• Biomass removal reduces fire severity, in some cases allowing prescribed fire or managed wildfire to be used after treatment. Reintroduction of low-severity fire is the most effective means of restoring resilience, which is particularly important if changes in climate occur.