Fuels Planning: Science Synthesis and

Integration

Environmental Consequences Fact Sheet: 14

Fuels Reduction and Compaction

United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

Research Note

RMRS-RN-23-14-WWW

November 2005

Fuels planning: Science synthesis and integration, an interagency research/management

partnership to support the Ten-Year Fire Plan,

led by Russell T. Graham, RMRS, and Sarah M.

McCaffrey, NCRS.

Synthesizing

Scientific Information

for Fire and Fuels

Project Managers

Environmental Consequences

Team Leader

Elaine Kennedy Sutherland

USDA Forest Service

Rocky Mountain Research Station

Missoula, MT

Deborah Page-Dumroese

USDA Forest Service

Rocky Mountain Research Station

Moscow, Idaho

Pacific Northwest

Research Station

Rocky Mountain

Research Station

What Is Compaction?

Moving equipment and logs over the surface of forest soils causes gouges and

ruts in the mineral soil, displaces organic matter, and can cause compaction. Compaction is measured by pore volume (the size of spaces between soil particles),

bulk density (soil weight per unit volume), soil aeration (the amount of air in the

soil), water infiltration (rate of water movement into the soil), and saturated

hydraulic conductivity (the ability of soil to transmit water). Compaction is the

component of soil productivity most influenced by forest management, but the

degree to which soils may be compacted depends on initial soil bulk density. For

example, low bulk density soils (such as volcanic ash-cap soils) are much easier

to compact than those soils with a high baseline bulk density.

Why Is It Important?

Concern over changes in soil productivity

after forest management activities is a topic

debated by forest managers and the public. Important components of this debate

include the use of mechanized equipment

to extract timber products, the number of

times equipment enters a stand, and the

subsequent soil compaction and recovery

times. One potential consequence of severe soil compaction is serious reduction

in site productivity. Ultimately, the degree

of compaction caused by harvesting or site preparation is affected by existing

soil properties (such as texture, organic matter, and water content).

Compacted soils have smaller pore sizes than noncompacted or undisturbed soils;

thus, changes in soil water content from compaction affect temperature flux,

which alters microclimatic conditions and leads to reduced root growth and stand

productivity. However, direct correlations of compaction and forest plant growth

are frequently unclear, because compaction is often associated with other soil

disturbances such as soil displacement, mixing, rutting, and changes in susceptibility to weed invasion.

Can Forest Soils Recover?

Various studies have shown that once compacted, it can take forest soils decades

to return to undisturbed levels of bulk density or soil strength (the ease with which

an object can be pushed into the soil); however, some forest soils recover more

quickly. Recovery rates are dependent on factors such as the number of repeated

stand entries, soil moisture conditions during harvest, soil texture, and rock-fragment content (Page-Dumroese and others, in review). Figure 1 shows the relationship of texture to recovery after 5 years.

Mechanized equipment can cause compaction, which some soils may take decades to

recover from (photo credit: Han-Sup Han).
The Fuels Planning fact sheets are based on preliminary findings. Information from fact sheets will be synthesized in an upcoming publication.

Environmental Consequences Fact

Sheets

Look for fact sheet topics from the Environmental Consequences

Team including information about the effects of fire behavior and

alternative treatment strategies, Wildlife Response Model, weed responses, riparian systems, soil erosion, restoration objectives, treated

spaces, the Fire Effects Information System (FEIS), and the First

Order Fire Effects Model (FOFEM).

Fuels Planning: Synthesis and Integration

This fact sheet is one in a series being produced as part of a larger

project supported by the USDA Forest Service to synthesize new

knowledge and information relevant to fire and fuels management.

Fact sheets address topics related to stand structure, environmental

impacts, economics, and human responses to these factors. Information in the fact sheets is targeted for the dry forests of the Inland

West, but is often applicable across broad regions of the country.

For more information, please visit our Web site at:

www.fs.fed.us/fire/tech_transfer/synthesis/synthesis_index

Selected References

Page-Dumroese, D.; Jurgensen, M.; Tiarks, A.; Sanchez, F.;

Fleming, R.; Kranabetter, M.; Powers, R.; Ponder, F.;

Stone, D.; Elioff, J.; Scott, A. In review. Soil physical

property changes on the North American Long-Term

Soil Productivity (LTSP) study sites: 1 and 5 years after

treatment. Canadian Journal of Forest Research.

Powers, R. F.; Alban, D. H.; Miller, R. E.; Tiarks, A. E.;

Wells, C. G.; Avers, P. E.; Cline, R. G.; Fitzgerald, R. D.;

Loftus, N. S., Jr. 1990. Sustaining site productivity in

North American Forests: problems and prospects. In:

Gessel, S. P.; and others, eds. Sustained productivity of

forest soils. Proceedings of the 7th North American Forest Soils Conference: 49–79.

What’s Being Done?

Mandates—like the National Forest Management Act

of 1976—have directed the USDA Forest Service to

protect the productive capacity of Federally managed

lands. The North American Long-Term Soil Productivity

(LTSP) study started in 1989 to examine long-term consequences of soil compaction and organic removal on

fundamental forest productivity (Powers and others 1990).

There are now more than 100 sites comprising the world’s

largest coordinated research network addressing basic and

applied science issues of forest management.

A research program

has been chartered to

address concerns over

possible losses of soil

productivity (photo

credit: Han-Sup Han).

Figure 1— Soil recovery 5 years after compaction. The 0-percent line represents preharvest conditions. Percent recovery 5 years after compaction

25

20

15

10

5

0

–5

–10

Fine sandy Sandy Clay Sand Loamy- Skeletal- Silt loam

loam loam sand loam (volcanic

ash-cap)