Vegetation Module Seth Bigelow, Michael Papaik, Malcolm North USFS Pacific Southwest Research Station
Jan 18, 2016
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 post-treatment 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 large-
tree reserves- 3 replicates- Stands of ~ 22 acres
Year
2003 2004 2005 2006 2007 2008 2009 2010
Can
opy
Cov
er (
%)
0
20
40
60
80
100
controlthin (light)thin (heavy)group selection
Canopy Cover, PSW ExperimentMeadow Valley
- Initial cover 70-80%
- Cover reduced to 50-60% in thinned stands
- Cover reduced to 10-20% in group openings
Light (mol m2d 1)
Ob
serv
atio
n d
en
sity
0.00
0.05
0.10
0.15
Pre-Treatment
0.00
0.05
0.10
0.15
Post-Treatment
0.00
0.05
0.10
0.15
10 20 30 40 50 60
3 yr Post-Treatment
ControlLight thinMed thinGroup
Understory Light, PSW ExperimentMeadow Valley
Canopy cover (%)
Ob
serv
atio
ns
> C
PI (
%)
0
5
10
15
20
40 50 60 70 80
Canopy Cover as Predictor of Area Available for Shade-Intolerant Regeneration
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
Survey
Fu
el w
eig
ht (
To
nn
es/
Ha
)
50
100
150
200
250
Control Light thin
Before After 3 yr after
Med. thin
Before After 3 yr after
50
100
150
200
250
Group
1 hr10 hrlitter100 hr1000 hrduff
Fuel Loads(dead groundand surface fuels)
-Treatments did notchange fuel loads
-Some differencesbetween survey years
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 coverby plant lifeform
-Species identification of dominant of each lifeform
-Pre-treatment and 3-yrpost-treatment surveys
Co
ver
(%)
10
20
30
40
Control Light thin
Pre Post
Med. thin
Pre Post
10
20
30
40
Group
ForbGraminoidShrubPineTolerantBroadLeaf
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
Density (#/m2)
Predicted Seedling Density, Group Selection Opening (provisional)
Density (#/acre)
ponderosa
sugar pine
incense cedar
Doug-fir
white fir
red fir
NortheasterlyHigh
50 100 150
NeutralHigh
SouthwesterlyHigh
ponderosa
sugar pine
incense cedar
Doug-fir
white fir
red fir
50 100 150
NortheasterlyLow
NeutralLow
50 100 150
SouthwesterlyLow
Seedling Density: Group SelectionOpenings, MeadowValley landscape
-High fir density at higher elevations
-Ponderosa(Jeffrey)density similar to White fir at lowerelevations
White fir annual growth and precipitation(Large trees)
Annual precipitation (inches/yr)
Ring
wid
th (m
icro
ns)
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