Vegetation Module
Seth Bigelow, Michael Papaik,
Malcolm North
USFS Pacific Southwest Research Station
Vision and Goals
• Determine ecosystem effects of current
silvicultural practices, especially those in Pilot
Project
• Develop predictive models of tree growth and
establishment
• Provide technical assistance to other modules
Vegetation Module
Research 2010
• PSW experiment, Meadow Valley: three-year posttreatment canopy and understory cover, fuel loads
• Seedling dispersion after disturbance: group selection
openings
• Neighborhood and Climate Determinants of Big Tree
Growth
PSW Experiment,
Meadow Valley
Treatments:
- Control
- Thin to 50% CC
- Thin to 30% CC
- Group selection with largetree reserves
- 3 replicates
- Stands of ~ 22 acres
Canopy Cover,
PSW Experiment
Meadow Valley
100
Canopy Cover (%)
80
- Initial cover 70-80%
60
- Cover reduced to
50-60% in thinned
stands
40
20
control
thin (light)
thin (heavy)
group selection
0
2003 2004 2005 2006 2007 2008 2009 2010
Year
- Cover reduced to
10-20% in
group openings
Pre-Treatment
Understory Light,
PSW Experiment
Meadow Valley
0.15
Control
Light thin
Med thin
Group
0.10
0.05
Observation density
0.00
Post-Treatment
0.15
0.10
0.05
0.00
3 yr Post-Treatment
0.15
0.10
0.05
0.00
10
20
30
40
2
50
1
Light (mol m d )
60
Observations > CPI (%)
Canopy Cover as Predictor of Area Available
for Shade-Intolerant Regeneration
20
15
10
5
0
40
50
60
Canopy cover (%)
70
80
Light Study: Conclusions
• Understory light changes slowly: it’s the same
three years after treatment as immediately
after
• Fuels-reduction thinning provides poor
conditions for Shade-Intolerant Regeneration
(~15% of area at 40% canopy cover)
• Group selection provides enough light for SIR,
even with large tree retention
Control
Light thin
Fuel Loads
(dead ground
and surface fuels)
250
200
Fuel weight (Tonnes/Ha)
150
-Treatments did not
change fuel loads
100
50
Med. thin
-Some differences
between survey years
Group
250
1 hr
10 hr
litter
100 hr
1000 hr
duff
200
150
100
50
Before
After
3 yr after
Before
Survey
After
3 yr after
Fuel Loads: Conclusions
- Low repeatability of Brown’s lines: consider
sticking to visual assessment (photo series)
- Fuels-reduction thinning doesn’t reduce dead
ground/surface fuels: further treatment (e.g.,
Rx. fire) needed
J. Katz
Understory Vegetation
-4-m diameter plots
-100 plots / stand
-Visual assessment of cover
by plant lifeform
-Species identification of
dominant of each lifeform
-Pre-treatment and 3-yr
post-treatment surveys
Forb
Graminoid
Shrub
Pine
Tolerant
BroadLeaf
Control
Light thin
Med. thin
Group
40
30
20
Cover (%)
10
40
30
20
10
Pre
Post
Pre
Post
Understory Cover: Observations
• It is what it was: treatments did not change
cover of any plant lifeform
• Its about the shrubs: they make up the largest
cover class
• It’s a fir farm out there: conifer recruitment
dominated by shade-tolerant species
Seedling Dispersion
(with Michael Papaik)
• Goal: develop models that spatially predict
seedling density after disturbance
• Requires seedling counts along transects in
mapped stands
• “Disturbance” types: high & low severity
fire, salvage, group selection
Predicted Seedling Density, Group Selection Opening (provisional)
Density
(#/m2)
50
High
Northeasterly
100
High
Neutral
150
Seedling Density:
Group Selection
Openings, Meadow
Valley landscape
High
Southwesterly
red fir
white fir
Doug-fir
-High fir density at
higher elevations
incense cedar
sugar pine
ponderosa
Low
Northeasterly
Low
Neutral
Low
Southwesterly
red fir
-Ponderosa(Jeffrey)
density similar to
White fir at lower
elevations
white fir
Doug-fir
incense cedar
sugar pine
ponderosa
50
100
150
50
Density (#/acre)
100
150
White fir annual growth and precipitation
Ring width (microns)
(Large trees)
Annual precipitation (inches/yr)
Neighborhood and Climate
Determinants of Big Tree Growth
• All species grew faster in wet years
• No species were sensitive to density of
neighboring trees
• Temperature: White fir, Doug-fir, Cedar grow
faster in warm winters, slower in warm springs
• Pines grew more slowly with warm late
summer temperatures
Conclusions
• Cover and understory light change slowly
• Fuels-reduction thinning (FRT) is a stop-gap
measure, doesn’t reduce ground/surface fuels
• FRT/GS does not hurt understory plants, or do
them much good
• Group Selection is increasing shade-intolerant
regeneration at lower elevation sites
• Large tree growth responds to climate
Acknowledgments
• Funding: USFS Region 5 & National Fire Plan
• Cooperators: Small mammal module (canopy
photos), Gerrard (graphics), Parker, Fuller,
Bednarski (NEPA), Baldwin (statistics), Caum
(dendrochronology)
• Support: Stine, QLG
• Field work: Salk, Perchemlides, Livingston,
many others
End