Monitoring Impacts of Ground-Based Thinning on Soil Quality in a

Late Seral Reserve

D.H. Young PSW Research StationR.F. Powers PSW Research StationB.L. Rust Shasta Trinity National Forest

Iron CanyonArea

Shasta-Trinity National Forest

Eastern KlamathGeology

3000 ft. Elev.

70-80 in. MAP

Boomer seriesUltic Haploxeralf

loam/clay loam

18” A horizon

Db ~ 0.76

Site Index 25 m (50 yr)

IRON CANYON LATE SERAL RESERVE

Mixed Conifer-Black Oak/Dogwood70-80 Years, Even-agedBasal area 100-180 ft2/acreOverstocked and Fuel Loaded2800-3000’ elevation / 70-80” MAP

LSR THINNING PRESCRIPTION

• Thin from below (May 2001)

• Retain 50-60 % crown cover • Retain older, mature trees

• Favor ponderosa pine for eagle nests

• Remove 80% of fuel ladder• Mechanical harvest -

Timbco feller buncherrubber tired grapple skidder

Are these impacts

important??

HarvestedIn May

Disturbance -101• EXTENT

% area, depth

• SEVERITYundisturbed extreme

Disturbance -101• EXTENT

% area, depth

• SEVERITYundisturbed extreme

• DISTRIBUTIONdispersed concentrated

• DURATIONshort term long term

mitigation? natural

recovery?

Harvest Equipment x

Timing of Operations x

Fine Textured Soils =

SOILS CONCERN

Harvest Equipment x

Timing of Operations x

Fine Textured Soils =

SOILS CONCERN

Did we meet the soil standards??

National Forest Soil Scientists are Charged with Monitoring Management Impacts

Did we meet the soil standards??How do we go about monitoring??

National Forest Soil Scientists are Charged with Monitoring

There are not clear protocols.This is a problem.

Basic Monitoring Approach

1. STRATIFY THE AREA (extent)Disturbance Classes

2. ASSESS EACH CLASS (severity)Bulk Density, Penetrometer

3. ASSESS SAMPLING EFFECTIVENESSStatistical Significance of Estimates

4. ASSESS THE IMPORTANCERegional Standards = ? = Ecological Impacts

National Forest Soil Scientists are Charged with Monitoring

There are not clear protocols.This is a problem.

LUMPER

SPLITTER

Iron Canyon Soil MonitoringDetermining Disturbance Extent

Disturbance Classes• LOW

forest floor completely intact, no sign of traffic

• MODERATEforest floor disturbed, but not a skid trail

• HIGHobvious skid trails

Light

Moderate

Heavy

100 ft Transect

WE AGREED UPON DISTURBANCE CATEGORIESAND LAID OUT 100-FT TRANSECTS

Unit Proportion by Disturbance ClassIron Canyon Harvest Unit 5/6/02

high34%

low34%

moderate32%

Disturbances were partitioned about equally

Iron Canyon Soil MonitoringDetermining Disturbance Extent

Soil pit in “High disturbance” fine roots through A/AB to Btplaty structure thru A horizons

A horizons

Bt horizons

Soil pit in “Low disturbance”forest floor intact, little compaction in A horizon

QUALITATIVE

Iron Canyon Soil MonitoringDetermining Disturbance Severity

QUANTITATIVE

Disturbance Category: Low Mod High units

bulk density 0.89 0.94 1.01 g/cm3

Iron Canyon Soil MonitoringDetermining Disturbance Severity

Averages by Disturbance Category (10-20 cm depth)

Disturbance Category: Low Mod High units

bulk density 0.89 0.94 1.01 g/cm3

Iron Canyon Soil MonitoringDetermining Disturbance Severity

Averages by Disturbance Category (10-20 cm depth)

Region 5 Standard: 10% Porosity Reduction

Initial Db: 0.89

Threshold Db: 1.06

RECORDING PENETROMETER

Many times faster than bulk density

Simulates what roots experience

Measures strength at 15 mm intervals to 60 cm depth

Electronic files

Strength Profiles by Disturbance ClassMay 2002

0

100

200

300

400

5000 500 1000 1500 2000 2500

SOIL STRENGTH (kPa)

DEP

TH (m

m)

lowmoderatehigh

Iron Canyon Soil MonitoringDetermining Disturbance Severity

Strength Profiles by Disturbance ClassMay 2002

0

100

200

300

400

5000 500 1000 1500 2000 2500

SOIL STRENGTH (kPa)

DEP

TH (m

m)

lowmoderatehigh

Iron Canyon Soil MonitoringDetermining Disturbance Severity

Disturbance Category: Low Mod High units

bulk density 0.89 0.94 1.01 g/cm3

soil strength 1085 1348 1801 kPa

Iron Canyon Soil MonitoringDetermining Disturbance Severity

Averages by Disturbance Category (10-20 cm depth)

Disturbance Category: Low Mod High units

bulk density 0.89 0.94 1.01 g/cm3

soil strength 1085 1348 1801 kPa

Iron Canyon Soil MonitoringDetermining Disturbance Severity

Averages by Disturbance Category (10-20 cm depth)

No Regional Standard.

Root activity inhibited: >2000

Root activity ceases: >3000

Disturbance Category: low mod high units

bulk density 0.89 0.94 1.01 g/cm3

soil strength 1085 1348 1801 kPa

Iron Canyon Soil MonitoringDetermining Disturbance Severity

Averages by Disturbance Category (10-20 cm depth)

Monitoring indicates the thinning operation was conducted in compliance with R5 soil standards

Disturbance Category: low mod high units

bulk density 0.89 0.94 1.01 g/cm3

soil strength 1085 1348 1801 kPa

Iron Canyon Soil MonitoringDetermining Disturbance Severity

Averages by Disturbance Category (10-20 cm depth)

Monitoring indicates the thinning operation was conducted in compliance with R5 soil standards

Although.... We lacked a true undisturbed area to use for baseline comparison.

What’s the site condition before entry?

Was it truly “pristine”?Or did it come with “baggage”?

Does legacy disturbance matter? Or, is “natural recovery” adequate to mitigate old disturbance?

IMPORTANT QUESTIONS

What’s the site condition before entry?

Was it truly “pristine”?Or did it come with “baggage”?

Does legacy disturbance matter? Or, is “natural recovery” adequate to mitigate old disturbance?

Are there cumulative effects?

IMPORTANT QUESTIONS

Site 1

Site 2

Iron Canyon

Watershed

Site 12001 Harvest

Site 22003 Harvest

Pre-harvestStand

Conditions

Overstockedand

Fuel Loaded

40 YEAR DISTURBANCE

LEGACY

1960’s EraSkid Trails

40 YEAR DISTURBANCE

LEGACY

1960’s EraSkid Trails

Dedicated for permanent traffic

system??

Pre Harvest (Residual) DisturbanceUnit Proportion by Disturbance Class

undist67%

dist22%

skid11%

Iron Canyon II Soil MonitoringDetermining Disturbance Extent

Disturbance Category: undist dist skid units

Bulk density 0.76 0.79 0.90 g/cm3

Iron Canyon II Soil MonitoringPre-Harvest Residual Disturbance

Averages by Disturbance Category (10-20 cm depth)

Region 5 Standard: 10% Porosity Reduction

Initial Db: 0.76

Threshold Db: 0.95

Disturbance Category: undist dist skid units

Bulk density 0.76 0.79 0.90 g/cm3

Strength(10 month average)

984 1534 2314 kPa

Iron Canyon II Soil MonitoringPre-Harvest Residual Disturbance

Averages by Disturbance Category (10-20 cm depth)