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)