Silvicultural experiments onPringle Falls Experimental Forest

SilviculturalSilvicultural experiments onexperiments onPringle Falls Experimental ForestPringle Falls Experimental Forest

Creating Stand-level Prescriptions to Integrate Ecological and Fuel Management Objectives for

Dry Forests of the Eastern Cascade Range

13-15 October 2009 Andrew Youngblood

PNW Research Station, LaGrande OR

Creating Stand-level Prescriptions to Integrate Ecological and Fuel Management Objectives for

Dry Forests of the Eastern Cascade Range

13-15 October 2009 Andrew Youngblood

PNW Research Station, LaGrande OR

OutlineOutline

• Physical setting and history of Pringle Falls Experimental Forest (PFEF)

• Past and ongoing research focused on ponderosa pine

• New research opportunities in mixed conifer forests

Physical settingPhysical setting• Distribution of

ponderosa pine• Network of

experimental forests

LocationLocation• Deschutes NF• 4477 hectares

(11,055 acres)

Physical settingPhysical setting• Representative of low to mid-elevation portions of

High Cascades physiographic province• Shield volcanoes (buttes) extending above ancient

lake basin• Soils derived from 2 m aerially deposited pumice and

ash• Mean annual

precipitation 600 to 1000 mm

Forest typesForest types• Ponderosa pine on most slopes• Lodgepole pine on flats and benches• Sugar pine, western white pine, grand fir, Douglas-fir,

mountain hemlock on higher north aspects • Riparian shrubs

along Deschutes River

History of PFEFHistory of PFEF• Selected in 1914 by

Thornton T. Munger• Created May 20, 1931 by act

of Chief Robert Y. Stuart• Established as a center for

silviculture, forest management, and insect and disease research in ponderosa pine forests east of the Oregon Cascade Range

Stand structure in early 1900sStand structure in early 1900s

Early 1930sEarly 1930s

Shevlin-Hixon and Brooks-Scanlon Company mills on Deschutes River in Bend each were cutting 200 million bdft a year

PFEF research mission, 1938PFEF research mission, 1938• Methods of cutting in old-growth ponderosa pine• Methods of thinning, pruning, and other stand

improvement in immature stands• Methods to convert low quality lodgepole pine

stands to a useful forest• Methods of protecting forests against fire and

insects• Methods of range management to improve forage

resources

OldOld--growth structure and dynamics growth structure and dynamics

• Keen 1936. Relative susceptibility of ponderosa pine to bark-beetle attack. J. For. 34: 919- 927.

• Keen 1940. Longevity of ponderosa pine. J. For. 38: 597- 598.

• Keen 1943. Ponderosa pine tree classes redefined. J. For. 41: 249-253.

SilviculturalSilvicultural cutting methodscutting methods

• Mowat 1961. Growth after partial cutting of ponderosa pine on permanent sample plots in eastern Oregon. PNW RP 44.

• Kolbe and McKay 1939. Seven methods of cutting tested at Pringle Falls. PNW RN 27.

• Mowat 1948. Selection cutting reduces ponderosa pine losses at Pringle Falls. PNW RN 45.

Methods of cutting studiesMethods of cutting studies• Maturity selection developed to

limit bark beetle losses• Improvement selection

developed in southwest to limit wind, lightening, and dwarf mistletoe losses

• Small tree component ignored in northwest, removed in southwest

• Controversy subsided by 1960 due to increased interest in even-aged systems

Transition to evenTransition to even--aged management aged management in 1950in 1950--1960s1960s• Can overstory be removed and sapling understory

retained?• Can saplings be

released to grow?• Does shrub

competition restrict sapling growth?

Ponderosa pine spacing study Ponderosa pine spacing study in 1959in 1959• Overstoy of 20 tpa, 25 in. dbh• Understory 7000 tpa, 1 in. dbh, 40-70

years old• 5 tree spacings with 6 replicates

6.6 ft. (1,000 tpa)9.3 ft. (500 tpa)13.2 ft. (250 tpa)18.7 ft. (125 tpa)26.4 ft. (63 tpa)

• Shrubs controlled in 3 reps

Growth of pine saplingsGrowth of pine saplings• Barrett 1965. Spacing and

understory vegetation affect growth of ponderosa pine saplings. RN PNW-27.

• Barrett 1982. Twenty-year growth of ponderosa pine saplings thinned to five spacings in central Oregon. RP PNW-301.

• Oren et al. 1987. Twenty-four years of ponderosa pine growth in relation to canopy leaf area and understory competition. For. Sci. 33: 538-547.

Spacing studySpacing study• Careful logging led to survival of regeneration and

reduced regeneration costs• Height and diameter growth of released saplings

accelerated after about 4 years• Increased spacing resulted in increased tree growth• Removal of competing vegetation resulted in

increased soil moisture and increased tree growth

Spacing study continuedSpacing study continued• Busse et al. 1996. Changes in ponderosa pine site productivity

following removal of understory vegetation. SSSAJ 60: 1614-1621.• Zhang et al. 2006. Growth and

development of ponderosa pine on sites of contrasting productivities: relative importance of stand density and shrub competition effects. CJFR 36: 2426-2438.

Spacing study continuedSpacing study continued

• Soil N and C greater with understory vegetation after 35 years

• Periodic volume growth declined from 1985 to 1994, similar to sites in northern CA because of confounding effects of mortality, drought, inter-tree competition, and insect defoliation.

• Tree-shrub competition shifted to tree- tree competition.

Past research at Pringle Butte, PFEFPast research at Pringle Butte, PFEF

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Lookout Lookout Mountain unitMountain unit

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Pipo/Putr-Ceve/Cain

Pipo/Putr-Ceve

Abgr/Ceve-Arpa

Abgr/Ceve/Cain

Abgr/Arpa

Lookout Mountain UnitPringle Falls Experimental Forest

4040

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4240 ¯0 500 1,000250 Meters

Current stand structureCurrent stand structure

• Closed-canopy forest, little major disturbance since stand-replacement fires in 1845 and 1890

• Buffer the Levels-of-Growing-Stock Study and the Ponderosa Pine-Grand Fir Spacing Study to prevent loss from insects and fire

• High and increasing probability that Lookout Mountain will support a landscape-scale western pine beetle/mountain pine beetle outbreak or wildfire

Forest dynamics after thinning and fuel reduction at Lookout Mountain Lookout Mountain • Refine management options for restoring resiliency

in ponderosa pine ecosystems• Evaluate the effects of thinning and fuel reduction on

long-term susceptibility to fire, insects, wind, climate change, and other forest disturbances

Proposed research questionsProposed research questions1. How does the residual stand structure resulting from

a set of fuel reduction treatments interact locally with wind to cause additional structural changes?

2. How does the dominant shrub, giant chinquapin (Chrysolepis chrysophylla), respond to a set of fuel reduction treatments?

Research questionsResearch questions

3. What set of fuel reduction treatments best accelerate the development of large trees while reintroducing natural disturbance processes that provide greater ecosystem resiliency?

4. What is the influence of climate change interacting with a set of fuel reduction treatments on vegetation dynamics and forest structure?

Research questionsResearch questions

5. Can single cohort stands be readily converted to multi- cohort stands?

6. Do multi-cohort stands share the same risks of multiple, interacting stresses as single-cohort stands?

Lookout Mountain study designLookout Mountain study design

Pipo/Putr-Ceve/Cain

Pipo/Putr-Ceve

Abgr/Ceve-Arpa

Abgr/Ceve/Cain

Abgr/Arpa

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Unit 21Unit 25

Unit 24

Unit 11

Unit 12

Unit 14

Unit 13

Unit 15Unit 32

Unit 35Unit 34Unit 31

Unit 33

Unit 44

Unit 41

Unit 42

Unit 43

Unit 45

¯0 500 1,000250 Meters

Proposed treatmentsProposed treatments

1. Thin from below to the Upper Management Zone (UMZ), mow and underburn

2. Thin from below to 75% of UMZ, mow and underburn3. Thin from below to 50% of the UMZ, mow

and underburn4. Regeneration cut to 75% of the UMZ to

begin transition to a multi-cohort stand structure

5. Retain for near-term the current structure

Northern Spotted Owl habitatNorthern Spotted Owl habitat• Opportunity to assess changes in forest structure

over time• Shifts in vegetation patterns with changing climate• Shifts in vegetation structure with treatments