opportunities for restoring second growth ecosystems in staney creek: scientific principles

Opportunities for Restoring Second Growth Ecosystems in Staney Creek: Scientific Principles

Acknowledgements

• U.S. Forest Service, Pacific Northwest Research Station

• Tongass National Forest, Thorne Bay Ranger District

• The Nature Conservancy

Funding provided by:

Fieldwork and analysis: Dee Casey, Kim Hastings, Mike Ausman

First Some History

Its hard to know where you are going or where to go if you don’t know where you have been!

Staney Creek 1976

What Made Staney Creekso Special in the

1970’s?• Large concentration of high timber volume

• Easy accessibility with new road system

• High value watershed for fisheries and wildlife (and recreation)

Unique disturbance ecology:Exposure to very infrequent

buthigh intensity winds

Implications of Disturbance

• Series of high wind events led to establishment of many high-volume even-aged forests- with exceptional economic value

• These same ecological factors led to challenges in controlling wind damage to residual stands and ultimately led to large clearcuts

Staney Creek 2009: extensive older second

growth forests

Forest Resource IssuesCreated by Second-

Growth• Secondary forests provide poor habitat for many wildlife species

• Poor connectivity between high elevation forest and critical winter range for wildlife

• Economic costs and ecological implications of roads

• Economics of wood utilization• Riparian habitat degradation

Wildlife habitat in forests

• Vegetation structure• Habitat Connectivity• Forage quality• Microclimate and soils/geology

Primarily a function of:

Vaccinium parvifolium

Shaheen Creek

Greatest overall structural diversity and understory Development usually found in old-growth habitats

Older Secondary Forests provide poor habitat because:

• Little browse (Vaccinium spp.)

• Poor cover by nutrient-rich forbs

• Less structural diversity

• Dense canopies provide little light at understory level

Key challenges for forest understory

plants• Low or variable sunlight • Less thermal energy during day• Little wind for pollen/seed dispersal

• Competition with trees for nutrients and moisture

• Few “safe sites” for establishment of new seedlings

Lots of other examples of managed forests providing poor habitat - but effects transient

Lots of other examples of managed forests providing poor habitat - but effects transient

Scots pineplantation

30 years 40 years

130 yrs 400 yrs

Alaback (1982)

If shade and tree density is the problem

then is thinning the solution?

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CONTROLLIGHT

MEDIUMHEAVY

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500

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BIO

MA

SS

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STAND AGE

12 YEAR RESPONSE OF SHRUBS TO THINNING

Problems with fix-spaced thinning

• Transient response (10-15 years)

• Greatest effect in intermediate spacings (10-14’)

• Older stands with poor shrub response

Present Condition and Trends

• Dense older second growth forest dominates watershed which constrains wildlife habitat for many key species

• Without management treatments it is unlikely that wildlife habitats will change for at least 50 years

• Residual old growth forest patches of key importance

• Thinning can improve habitat, but effects are transient

Photo: Mike Ausman

Desired Future Conditions

• Improve wildlife habitat•Increase overall biodiversity•Increase landscape connectivity•Increase economic value of forest and opportunities for niche markets

How can we best restore understory biodiversity

to second-growth forests?

1. Provide more resources through fixed-spaced thinning

2. Create a more heterogenous environment through variable spaced thinning or canopy gaps

3. Some combination of these approaches?

Biodiversity

Resources (light, nutrients)

Habitat heterogeneity

Landscape connectivity

EvolutionaryDiversification& history

Biodiversity

Resources (light, nutrients)

Habitat heterogeneity

Landscape connectivity

Evolutionarydiversification& history

Plant species richness closely predicted at regional scalesFrom energy availability (actual evapotranspiration) (Currie 1999 Am. Nat.)

Management homogeneity

Natural disturbance heterogeneity

Why what works for carrots may not work as well for

forest ecosystem

biodiversity

Dipterocarp tropical rainforestIndonesia (S. Siebert)

Gap dynamics in tropicalRainforests -- helps explain High diversity

(Orians 1981)

Small canopy gaps:Dominant disturbanceRegime: 1-4/trees,1-4% per year:

Creates stand heterogeneity

(Ott & Juday 2002)

Extreme landscape heterogeneity

How does thinning affect habitat

heterogeneity in these forests?

• Compared fixed-spaced thinning and diameter-limit thinning on well and poorly-drained sites

• Evaluated initial effects on canopy & understory structure

Alaback & Casey, ms.

Effects of thinning on spatial structure

Following thinning:

• Enhanced or suppressed structural heterogeneity depending on initial stand condition

• Diameter-limit approach may enhance heterogeneity, but more replication is needed to determine generality of this result

Direct enhancement of heterogeneity: canopy

gaps• Canopy gaps established from 30’ to 150’ in diameter in critical wildlife habitat areas

• Effects contrasted with thinned and unthinned forest landscapes

• Summers 2008-9 measured 20 year response to treatments on 75 sites

CANOPY GAP THINNED FOREST

Photos: Mike Ausman

CANOPY GAP UNTHINNED FOREST

Photos: Mike Ausman

B

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GAP CONTROL0

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B

GAP CONTROL0

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20-Year Understory Response to Gap Treatments

(2008 data only)

• Restoration of understory biodiversity a difficult and long-term task• Thinning alone will not restore diversity or function• Canopy gaps show more consistent results than thinning• The most promising approach is to combine thinning and gap treatments at the stand and landscape scale and tailor for management goals

The Olympic Model of Second Growth Management

• Goal is to create complex multi-canopy layer forest that provides habitat for old-growth dependent wildlife species

• Create control (unthinned) patches as cover habitats, and for species that grow in shade

• Create matrix of thinned forest• Establish canopy gaps within the thinned matrix

• Provide greatest habitat patch diversity at stand scale and greatest species diversity within gap treatments

(after Harrington et al. 2005)

Canopy gap

Skip

Thinned matrix

The “Olympic Model” After Harrington et al. 2005

Shaheen Creek

Old growth always will be distinct from managed second growth

Key Points• Staney Watershed dominated by second growth with poor wildlife habitat values

• Biological value of forests can be significantly enhanced through thinning and canopy gaps

• Effects of thinning are transitory, but canopy gaps have longer-term effect

• Residual old growth forests play key role in landscape diversity

• Greatest promise lies in combining treatments at both stand and landscape scales to promote both wildlife habitat diversity and a diversity of other resource benefits