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