Different effects of thinning and burning on Sierran mixed-conifer ecosystems

Malcolm North, USFS, Sierra Nevada Research Center, Davis, CA

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TEAKETTLEEXPERIMENT

ECOSYSTEM(10 ac)

WATERSHED(3000-5000 ac)

FIRESURROGATE

STUDY

STAND(50-100 ac)

LANDSCAPE(up to 500,000 ac)

KINGS RIVERPROJECT

Large-scale fire movement & behavior, spotted owls

Water flow & nutrients; forest carnivores; birds; uneven-aged mgt.

PLUMAS /LASSEN STUDY

Stand dynamics, regene., management options; animals w/small home rangesSoils; microclimate; respiration; succession; food webs

Focus and Scale of Some of the Fuel Reduction Experiments in California

Thinning Level: No Burn Understory Burn

None Control Burn Only

25 cm < thin <76 cm

Thin from below/No Burn

Thin from below/Burn

25 cm < thin & leave 22 large t/ha

Overstory thin/No Burn

Overstory thin/Burn

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18 plots, 4 ha each, 3 reps of each of the 6 treatments

Teakettle Location, Design, Plot Layout and Timeline

• Burned November 2001, ‘off season’, for containment & air quality

Pretreatment data(2-3 yrs for all studies)

Treatments

Post-treatment data (2-3 yrs for all studies)

1998

1999

2000

2001

2002

2003

2004

Monitoring (5-20 yrs)

Thinning Effects (using all trees in a 4 ha plot)

Understory: 25 cm< thin < 76 cmOverstory (shelterwood): Thin > 25 cm & leave 22 large tree/ha

Teakettle’s Focus: Ecosystem Structure, Composition and Function

Univ. of California, Berkeley, CATom Bruns, Antonio Izzo, Agneta Plamboeack, Todd Dawson

Mycorrhizal Diversity/Water Movement using Stable Isotopes

Univ. Metropolitan, San J uan, PRHeather EricksonSoil Nutrients

Univ. of Toledo, OHJ iquan Chen, Siyan Ma & Suong RhuMicroclimate, Soil Respiration

I NSTITUTIONPRI NCIPAL I NVESTI GATORSTUDY

Pacific Southwest Research, Davis, CAMalcolm North, J im InnesTree/Shrub Mortality & Growth, Truffles, Cones, Coarse Woody Debris, and Diameter Growth

Calif. State Univ. Fresno, CARuth KernSeed Dispersal

Univ. of California, Davis, CAMatthew Hurteau & Malcolm NorthGlobal Climate Change & Tree Demography

Univ. of California, Davis, CARebecca Wayman & Malcolm NorthUnderstory Herb & Shrub Diversity

Univ. of Washington, Seattle, WABrian Oakley, J erry Franklin & Malcolm North

Nitrogen Dynamics, Frankia Diversity & Response to Fire

Univ. of California, Davis, CATom RamboLichen Growth & Dispersal

Univ. of Washington, Seattle, WAJ im Marra & Bob EdmondsSoil & CWD Invertebrates

Univ. of California, Davis, CAMarc Meyer, Doug Kelt & Malcolm NorthFlying Squirrels, Chipmunks & Truffles

Univ. of California, Davis, CADavid Rizzo, Tom Smith, Tricia MaloneyTree Pest & Pathogens

Louisiana State Univ, Baton Rouge, LATim SchowalterCanopy Invertebrates

Pacific Northwest, Forest Inventory Analysis, Corvallis, OR

Andrew Gray & Harold ZaldTree Regeneration & Soil Moisture

Univ. of California, Davis, CAMichael Barbour, Rob Fiegener, Fire History

Michigan Technology University, Houghton, MI

Marty J urgensonDecomposition

Univ. of California, Berkeley, CATom Bruns, Antonio Izzo, Agneta Plamboeack, Todd Dawson

Mycorrhizal Diversity/Water Movement using Stable Isotopes

Univ. Metropolitan, San J uan, PRHeather EricksonSoil Nutrients

Univ. of Toledo, OHJ iquan Chen, Siyan Ma & Suong RhuMicroclimate, Soil Respiration

I NSTITUTIONPRI NCIPAL I NVESTI GATORSTUDY

Pacific Southwest Research, Davis, CAMalcolm North, J im InnesTree/Shrub Mortality & Growth, Truffles, Cones, Coarse Woody Debris, and Diameter Growth

Calif. State Univ. Fresno, CARuth KernSeed Dispersal

Univ. of California, Davis, CAMatthew Hurteau & Malcolm NorthGlobal Climate Change & Tree Demography

Univ. of California, Davis, CARebecca Wayman & Malcolm NorthUnderstory Herb & Shrub Diversity

Univ. of Washington, Seattle, WABrian Oakley, J erry Franklin & Malcolm North

Nitrogen Dynamics, Frankia Diversity & Response to Fire

Univ. of California, Davis, CATom RamboLichen Growth & Dispersal

Univ. of Washington, Seattle, WAJ im Marra & Bob EdmondsSoil & CWD Invertebrates

Univ. of California, Davis, CAMarc Meyer, Doug Kelt & Malcolm NorthFlying Squirrels, Chipmunks & Truffles

Univ. of California, Davis, CADavid Rizzo, Tom Smith, Tricia MaloneyTree Pest & Pathogens

Louisiana State Univ, Baton Rouge, LATim SchowalterCanopy Invertebrates

Pacific Northwest, Forest Inventory Analysis, Corvallis, OR

Andrew Gray & Harold ZaldTree Regeneration & Soil Moisture

Univ. of California, Davis, CAMichael Barbour, Rob Fiegener, Fire History

Michigan Technology University, Houghton, MI

Marty J urgensonDecomposition

Collaborators

1. What effect do shrubs have on forest succession and water dynamics?

2. Why is mixed conifer so strongly clustered? Are trees grouped by age cohorts?

3. Do significant reductions in canopy cover reduce regeneration survival and understory herb cover?

4. Did the fire and thinning treatments produce a desired diameter distribution?

Teakettle Results: Focus on 4 Vegetation Questions Relevant to Developing Thinning and Burning

Prescriptions

• Saplings and shrubs compete for shallow water in early summer

•Trees rely on deep water through summer drought

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Shrub (Arctostaphylos spp.)

(using isotope signatures of soil and plant water)

Manzanita

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Mycorrhizae ExclosureRoot ExclosureControl

1. What effect do shrubs have on forest succession and water dynamics?

From A. Plaemboeck

• Low tree seedling survival in shrubs and without root exclosure

• Shrubs become islands that can ‘lock’ a site against seedlings and herbs

2. Why is mixed conifer so strongly clustered? Are trees grouped by age cohorts?

Bonnicksen and Stone (1982) suggested pattern is due to grouped cohort age structure

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1813x abcox abmax cadex pijex pila

Are trees grouped by age cohorts?

•No: ages were not spatially autocorrelated (variogram not shown)

Krigged distribution of tree basal area in a 4 ha area

Depth to bedrock for the a 4 ha area, where deeper soils are in red.

(Determined by seismic survey)

Why is mixed conifer so strongly clustered?

• One influence may be that tree groups reflect the geomorphic template (depth to bedrock)

Note correlation between the grouping of tree basal area, mostly driven by clusters of large trees and the depth to bedrock

• Mortality episodic: associated with La Nina droughts

• Most mortality in areas of high density

• Significantly higher than expected mortality for large trees

• Are small/intermediate trees depleting deep soil water pockets?

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How Might This Explain Current Mortality Patterns?

* Significantly different than expected (Chi-square)

3. Do significant reductions in canopy cover reduce regeneration survival and understory herb cover?

Persistent gaps in mixed-conifer without regeneration and having few herbs

Surface temperature by Julian date (y axis) and hour (x axis) for 3% and 76% canopy cover

Post-treatment: Germinant Survivorship

•Burned treatments had higher pine germinant survival •Burn and thin treatments (BC and BS) also had the lowest white fir and incense-cedar survivorship• Herb cover and richness (not shown) significantly greater in all burned vs. thinned treatments, regardless of canopy cover reduction

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• Increased separation of sugar pine and white fir based on light level and soil moisture

Increased Micro-site Heterogeneity

Pre-Treatment Post-Treatment

Data and slide from Harold Zald and Andy Gray, PNW Research

Light

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#/stems by dbh and species on 20 ac

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Before fire suppression (1865) recruitment and mortality was ‘pulsed’ by fire and El Nino events

Hypothesized pre-fire suppression 'pulse' diameter distribution

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Current diameter distribution

4. Did the fire and thinning treatments produce a desired diameter distribution?

10-30 31-60 61-90 >90

Size Class (cm)

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VTM* (‘desired’ dist.)ControlBurn.onlyUnderstory.onlyUnderstory...BurnOverstory.onlyOverstory...Burn

4. Did the fire and thinning treatments produce a desired diameter distribution?

No: Not enough small and too many intermediate size trees taken

* VTM is >2400 vegetation type mapping plots collected in the early ’30’s

• Thinning alone ‘stalls’ herb development and does not favor shade-intolerant regeneration

• Fire’s important for reducing shrubs which are strong competitors with trees and herbs

• Group selection doesn’t appear to be needed

• Thinning treatments may need to target small trees in high density areas, particularly around large, old trees

• If prescribed fire is applied ‘off season’, thinning must be aggressive about cutting small trees

• Observation: Thinning prescriptions should stay focused on trees as fuels rather diameters or board feet

What did we learn at Teakettle?