Vegetation Module
Seth Bigelow, Michael Papaik,
Malcolm North
USFS Pacific Southwest Research Station
Canopy Cover as
Management Metric
• Hundreds of mentions in Sierran forest plans
• Determines understory light & microclimate
• Related to ecosystem service provision: water
yields, biodiversity, fire regime.
Forested Areas
Treated in
Meadow Valley,
2000-2009
How has canopy
cover changed in
areas treated since
HFQLG implementation?
Canopy Cover Change in Treated Areas
Meadow Valley CA, 2002 - 2009
0
50-60
Legend
Grey bar & strip title
show earlier (2000)
cover class.
20 40 60 80
60-70
Acres
800
600
400
Blue dots show how
area is classified
in 2009
200
70-80
80-90
800
600
400
200
0
20 40 60 80
Cover From Above (%)
Results
Many formerly
high-cover
areas now classified
as having lower
cover
(Aerial photo analysis,
USFS Remote Sensing Lab)
PSW Experiment, Meadow Valley 2007
• Treatments: light thinning (57% CC), heavy
thinning (49%), group with reserves (12%)
• 12 stands, each ~ 22 acres
• Microclimate measurements: fuel & soil
wetness, soil temperature.
• Statistical modeling of relationship between
canopy cover & microclimate
10-hr Fuel Wetness & Canopy Openness
Results:
Negligible effect
of canopy
openness on fuel
wetness
Midday Soil Temperature & Canopy Openness
2 cm depth,
mineral soil
Celsius to
Fahrenheit
15 C = 59 F
25 C = 77 F
Day of Year:
Aug 1 - 31 =
213 - 243
Results
Large linear increase in
midday soil temperature
as canopy openness
increases
Soil Wetness at Three Depths
Depths
0 – 15 cm (0 - 6 in)
15 – 40 cm (6 – 16 in)
40 – 70 cm (16 – 28 in )
Units
Volume of water per
volume of soil (m3 / m3)
Expectation:
Increased soil wetness after
thinning, because of decreased
transpiration.
Soil Wetness & Canopy Openness
40-70 cm
15-40 cm
0-15 cm
Results:
Deeper soils are
wetter
No increase in soil
wetness with
thinning, only with
group selection
Conclusions: Fire Implications
• US Forest Service’ fuels/forest health
treatments are lowering canopy cover
• More open forests will not increase fire
behavior by drying out fuels…
• …but hotter soils (& fuels) may increase
probability of accidental ignition.
Ecosystem Services & Health
• Findings don’t support the notion that
thinning trees will increase water yields,
an important ecosystem service
•Unchanged soil wetness after thinning
stands means more water per tree, thus
improved plant water status & resilience.
Now on to Michael Papaik’s
presentation…