An Introduction to Variable Retention Harvesting

BY: Ken Zielke, Symmetree Consulting Group Ltd January 20, Spokane Wash.For more info: kzielke@telus.net or www.symmetree.ca

The following people helped make this presentation possible :

Bryce Bancroft, Symmetree Consulting Group

Bill Beese, and MacMillan Bloedel (Weyerhaeuser) Ltd.

Mike Bragg and Tolko Industries, Hefley Creek, BC

Shannon Janzen – Coast Forest Conservation Initiative Group of Companies.

Jerry Franklin - University of Washington

Fred Bunnell and Laurie Kremsater, Univ of BC.

Jason Mogilefsky and Potlatch Corporation

Outline

1. What is variable retention (VR)?

2. Who is doing VR?

3. Benefits and Costs?

4. What is the ecological rationale for VR?

5. How does VR fit with traditional silvicultural systems?

6. Making VR work on the ground – planning layout etc.

7. Risks – such as windthrow.

So, What is variable retention?

How is it defined?

QUESTION:

Variable Retention:

• A general approach to silvicultural systems and harvesting across a landscape or management unit.

• Primary objective is ECOLOGICAL • to maintain biodiversity using retention

Variable Retention

Key points:• Retention is long term (rotation)• Retention is well distributed• Variable is a key – no set

patterns or amounts

Who is actually doing variable retention??

QUESTION:

The Pacific Northwest…

Early 1990’s Plum Creek Timber moves to reverse it’s “Darth Vader” image from the past.

The BC Interior: For a range of objectives

NW BC - 1991

Southern BC - 1991

The BC Interior: Current beetle epidemic

Chief Forester setGuidelines for stand level retention (10- > 25%)

Mid 1990’sAlberta Pacific – Northern Alberta• Retention in the boreal forest• For habitat and biodiversity

Northern Alberta – boreal forest

1998 – MacMillan Bloedel unveils “Forest Project”

BC Coast

Objective was all blocks with at least 10% retention over 5 years

1999-2005• Other Companies on the Coast

using some VR.

• Retention is now a key feature in a planning area that stretches along most of the Coast.

BC Coast

Other Parts of Canada:

2003 - Quebec

2003 - Ontario

OK – what’s in it for me as the landowner?

QUESTION:

Benefits for a small landowner

1. Helps address Social Concerns RE:– Ecological impacts of logging– Conservation of biodiversity– Other objectives – visuals?

2. Certification Requirements?• FSC?

OK, What’s the COST?

QUESTION:

VR Carries a Cost!

1. Less Volume and Growth– Wood left on-site

– Impacts on growth of regen

2. Increased Logging Costs

Volume production losses over a rotation:

• 20-30% less yield with 43 – 65 ft2/acre uniform dispersed (15-20 % of original volume):

Zielke et al.(2002), Acker et al. (1998) Di Lucca et al. 2004

• Clumped or grouped retention – significantly less impact with significant gaps between.

• 2-5% growth reduction in addition to the volume left behind.

Palik et al. 1997, Coates 1998, Wright et al. 1990, Drever and Lertzman 2001,

Di Lucca et al. 2004

Estimates of impact on regen growth

Weyco (BC Coastal) Study on for VR Harvesting Costs

• Added costs - $4.00 Cdn/m3 (range = 0 - $6.00) over and above clearcutting…or

• About $6.55 US / MBF

For:• 62% ground based• 28% cable• 10% helicopter

What exactly is the ECOLOGICAL RATIONALE for variable retention?

QUESTION:

Largely influenced by two ecologists / conservation biologists:

The idea to leave long term retention in BC Forests...

Jerry Franklin (University of Washington and USFS) Fred Bunnell

(University of BC)

Theme – Forest species adapted to natural patterns shaped through natural disturbances

• Even severe natural disturbances don’t remove all stand structures.

• These structures fulfill a key ecological role through time – biological legacies.

In the Coastal Temperate Rainforest:

• Small gaps dominate natural disturbance.

• Old forest biological legacies are pervasive on the landscape.

Amount and Distribution of Biological Legacies

• varies naturally by ecosystem and associated natural disturbance regime

Biological Legacies –post-disturbance function:

“Lifeboat” Species through development of next stand by providing:

• individual habitat structures, and

• intact habitat environments aggregates or groups

Biological Legacies –post-disturbance function:Enrichment of Established Stands:

• A greater diversity of retained structural elements may provide a greater diversity of habitats over time.

• So KEEP IT VARIABLE

Biological Legacies –post-disturbance function:Improved connectivity

• Good distribution “softens” the harvested (managed) forest matrix.

But – Can I just put all this retention on the edge of the cutblock?

Biological Legacies – Improved Connectivity

• Species that disperse widely often most at risk from large scale harvesting.

• Well-distributed retention makes the harvested matrix around protected areas less hostile – more easy to move through.

Connectivity – How’s the view?

You are are species that nests in old growth stands.

You don’t like being in the open too long as your enemies will get you.

AND

Mating season is near and it sure has been a long time since you had a … date

What if:

You travel widely to find food.

Connectivity – Landscape vs. Stand Level retention (in the harvested matrix).

• Well-distributed retention throughout harvested units REDUCES the need for large reserves at the landscape level.

• Because the harvested matrix has more habitat value.

Here is how it works…

1. Different species – different spatial and other needs.

2. Individual species – respond to influences differently at different spatial scales.

3. Processes at different scales – can be interdependent.

SO - Planning retention at multiple scales:

• helps promote the variability needed to best address the full range of species

• Provides managers with more flexibility to address a range of goals.

But I don’t see how VR fits with the traditional silvicultural systems

QUESTION:

• A planned program of silvicultural treatments during the whole life of the stand designed to achieve specific stand structural objectives.

Silvicultural Systems Definition

What Does this mean?

Silvicultural System Definition

An long-term approach to stand management that fits with:– Stand type– Ecological conditions

Translates into:

Expected outcomes

• Product volumes

• Product values

Designed to meet

Traditional Silvicultural Systems

Defined by:

1. Regeneration Methods– Planting– Natural

2. General Stand Structure– Even-aged– Uneven-aged

3. Approach to Harvest– Pattern– Timing– # of entries

FOCUS = TIMBER PRODUCTION

Traditional Silvicultural Systems

Even-aged Systems– Clearcut– Seed tree– Shelterwood

Resulting stand structure is EVEN-

AGED

Initial Harvesting in Several Entries

Traditional Silvicultural Systems

Selection Systems– Single-tree Selection

– Group Selection– Strip Selection

MULTI-ENTRIES - Resulting stand

structure is UNEVEN-AGED

Remember…

• A general approach to silvicultural systems and harvesting across a landscape or management unit.

Variable Retention:

• Primary objective is to maintain biodiversity.

• an umbrella term under which many silvicultural systems can be used

Remember Key attributes of a VR strategy…

• Retention is long term• Retention is well distributed• Variable is a key – no set patterns or amounts

Can be used with multi-entry systems?

Uniform Shelterwood with retention

After last entryAfter 1st entry

Douglas-fir

W. Larch

Group Selection with retention

Can be used with multi-entry systems?

On the BC Coast…

• A “new” silvicultural system• Designed to:

1. Ensure good distribution of retention

2. Credibly differentiate the approach from clearcutting

The Retention System was developed for Variable Retention

What is the Retention System?

Year 0

Year 25

• Retains a target amount of structure, such as live and dead trees and woody debris, for at least one rotation

• Provides structural diversity and forest or residual tree influence over the majority of a cutblock– “Influence” generally extends at least one tree length

from an edge

2001 - Mitchell and Beese, Forestry Chronicle

What is meant by forest influence?

Key Points:

• Ecological zone of influence around trees and edge

• 1 tree length

For retention systems:

• influence over the majority of the cutblock.

50%+ of harvested area

Ideal Retention Quality:

Ecological Value

A significant component of:

• Larger doms or vets (> 12 inches dbh)

• “Old features” – decay, large limbs, thick bark etc.

Long-lasting

• Windfirm

• Sufficiently healthy to function beyond the short term.

Safe

• Will remain safe for harvesting and planned follow-up operations.

SUMMARY: Remember…

Traditional Silvicultural Systems Defined by:1. Regeneration Methods

– Planting– Natural

2. General Stand Structure

– Even-aged– Uneven-aged

3. Approach to Harvest

– Pattern– Timing– # of entries

FOCUS = TIMBER PRODUCTION

SUMMARY: the retention system…

RETENTION Silvicultural Systems Defined by:

1. Retained timber for non-timber resources values– Habitat– Visuals or…

2. Ecological Influence– Leave trees– Edges

FOCUS is NOT TIMBER PRODUCTION

SUMMARY: variable retention…

Variable Retention IS AN APPROACH :• to long term retention of structural attributes across a landscape

and/or management unit

Silvi systems used include:

Mostly:– Retention systems, and– Traditional systems with reserved timber

But may also include:– A component of clearcutting

A VR approach must be tailored to fit with the local ecological conditions.

QUESTION:This is great on paper But how do we make it work on the ground?

Planning Retention at multiple scales

Example – Northern Alberta Boreal Forest

Large intense disturbances having relatively short return intervals

Landscape Remnants• 20-30 % - larger patches missed by burn and connected to unburned matrix.

Island Remnants within the burn• 3-15 % per disturbance patch (many unmappable)

From: Dave Andison’s Northern Alberta Work (2004)

Example – Northern Alberta Boreal Forest.

Planning Retention at multiple scales

The flexibility of retention at multi-scales

Actual Landscape retention - 42%

Inblock retention in adjacent blocks - 16 - 22%Landscape Remnants• 20-30 % - larger patches missed by burn and connected to unburned matrix.

Island Remnants within the burn• 3-15 % per disturbance patch (many unmappable)

From: Dave Andison’s Northern Alberta Work (2004)

Example – Western Boreal Forest.

Retention at multiple scales Example – Western Boreal Forest.

So, first learn about your natural disturbance regimes in the Inland Empire.

• Fire intensity, size and return intervals were naturally highly variable

• Ecological and topographical influences

• BUT still lots of overlap in time and space

Also

• Other gap disturbances (insects, disease, wind) on top of that.

Next consider the landscape level context.

Think about

• Recent disturbance

• Larger landscape level reserves

• Consider other management objectives and keep it variable

• don’t do the same thing everywhere

N. Idaho

Next consider the landscape level context.

N. Idaho

AT THE STAND LEVEL - Be clear on your objectives…

Special Habitat?Reduced Visual

Impact?

General Maintenance of Biodiversity?

Limited Hydrologic Impact?

Regeneration?

Other?

What you are trying to achieve?

Steps in Designing Stand Level Retention:

1. Management Objectives: Why are we leaving trees?

2. Stand Structural Design: What attributes are we looking for?

3. Stand Recce: Translating the Design to the Ground

5. Implementation Strategy: What do we need to do to make it work?

4. Developing silvicultural systems and retained structural options: Putting it all together:

• Leave tree opportunities• Patterns of harvest / leave trees• Available Harvesting Systems• Risk Assessment

What are your desired stand level conditions?

–Does this depend on the surrounding landscape?

–Can it be altered over time?

Based on your stand knowledge and objectives, are any of the following criteria relevant?

1. Degree to which the stand can be opened up in one entry?

2. Characteristics of potential leave trees?

3. Distribution of potential leave trees?

1. Management Objectives: Why are we leaving trees?

2. Stand Structural Design: What attributes are we looking for?

3. Stand Recce: Translating the Design to the Ground

5. Implementation Strategy: What do we need to do to make it work?

4. Developing silvicultural systems and retained structural options: Putting it all together:

• Leave tree opportunities• Patterns of harvest / leave trees• Available Harvesting Systems• Risk Assessment

Steps in Designing Stand Level Retention:

• CONTROL POINTS – to identify structural attributes, or areas to avoid when logging:

– Engineering– Economic– Biological

STAND RECCE: ID your Control Points

Control Points help determine the mix of leave tree options by:

• Locating opportunities for leaving structure

• Helping to integrate suitable engineering considerations.

1. Rock outcrops / talus

2. Snag concentrations

3. Large old veteran trees

What are biological control points (anchors)?

4. Terrestrial Riparian ecosystems

5. Identified special habitats

6. Less common trees

What are biological control points?

7. Less common ecosystems

8. Areas of high diversity

What are biological control points?

4. Designing the Silvicultural System and Harvest Plan

Objectives and Desired Stand Conditions

Stand Recce: •Control Points

•Existing General Stand Conditions

RISKS?

Operability and Available Harvesting Systems:

Silvicultural S

ystems??

CONSIDER: Operability and Available Harvesting Systems

Operability Issues

– % Slope

– Nature of Terrain

– Soil Issues

– Roadbuilding Issues

– Other?

Available Harvesting Systems

– Ground

– Cable

– Aerial

– Combinations

Opportunities for New Systems?

Consider…

VR TIP at the landscape level

• Think carefully about leaving any in blocks less than 10 acres in size.

Consider this larger block on the Coast

If possible - Avoid excessive retention in small blocks

VR TIP - Focus most retention in groups and clumps

Group (0.5 acre +)

Clump (less than 0.5 acre)

• With lots of space between them

• Provides more support to resist wind• Contributes value for biodiversity• Combine with smaller trees if possible

VR TIP - Use larger Douglas-fir, Larch, Pine, Aspen (or other broadleaf trees) as anchors for clumps

• They developed in the stand naturally as a structural unit

VR TIP - Key on natural clumps to build retention

• But want to avoid going overboard

VR TIP - Use larger groups for broadleaf trees (where it fits with objectives).

• Aspen especially is highly desirable for biodiversity.

• Can become excessive where there are lots of opportunities to leave trees

VR TIP - AVOID generic approaches – “leave all trees under or over a certain size”

VR TIP - Mix in occasional individual trees

• Larger trees that originated above the general stand canopy

• Remember intent

VR TIP - Dispersed trees (and clumps) – should be widely spaced (unless multi-entry silvicultural system)

• Intent ?• Impact on developing regen?• Site prep?

• Usually 1 - 2 tree heights• Avoid in small openings

VR TIP - Dispersed trees (and clumps) – should be widely spaced

BetterOK

• Indicate on logging plan

VR TIP - Plan the distribution of groups, clumps and individual trees.

Locate 2-3 Fir clumps or vets here

• Within and between blocks

VR TIP - Strive for variation in amounts and patterns

2nd pass area

2nd pass area

2nd pass area

Riparian area

Riparian area

Windfirm clumps

Putting it together – A layout example

Eastside BC example – Williams Lake

Diverse Broadleaf / Root Rot

Large Doug-fir vets

1st entry prep cut – remove pine

UBC Alex Fraser Research Forest

Diverse Riparian Veg

Blah blah blah WhateverIt’s all just going to blow down!

QUESTION/ SKEPTICISM

CONSIDERATIONS:• Risk to Achieving Objectives (Timber and Non-timber)• Financial Risk – is harvesting profitable?• Windthrow Risk?• Insect and Disease Losses – now and over time?• Fire Risks – short and long term?

When Options Fully Developed - Assess Risk

RISK ASSESSMENT

VR TIP - Assess windthrow risk (likelihood) and associated consequences

Choices?:• Change layout• Plan for salvage• Leave it• Windproofing treatment

• at exposed edges, and in uniform areas with dispersed retention

Windthrow Hazard and Risk Assessment - BC

Symmetree Consulting Group• With Dr. S. Mitchell, Univ of BC

Soils

Windthrow Triangle

Expo

sure

Stand

Site Hazard

Low Moderate High

Exposure

Low

Mod

erat

e H

igh

Soi

ls

Overall Hazard

Low Moderate High

Site HazardLo

w M

oder

ate

Hig

h

Sta

nd

-Low -Moderate -High

VH

Windthrow Workshop –Assessments and your plan

1 Field Recce

• ID areas of HIGH (moderate) hazard

• ID areas where impact is HIGH

2 Prelim. Paper plan

3 SP Fieldwork and Layout

• Confirm wind hazard and risk

• Edges & Dispersed retention

4 Determine Amount of Expected Windthrow

Is it acceptable? Management Risk based on Consequences?

OPTIONS:

• Salvage

• Alter Layout

• Treat

IF NOT:

Windthrow Workshop

Effects of Cutblock Design on Treatment RiskAmount of “Fetch” between edges

(Rollerson and Beese, 2002) Wind

wind

1. based on estimates in a sample of 2994 plots looking at windthrow 25 m into edge• 98 harvested blocks - after 2 winters of storms

Does VR just blowdown?

Average windthrow along external blk edges1:

Average = 11%

Average windthrow in large group/patch edges1:

Average = 15% 1 ha+

Average windthrow in groups/clumps: Average = 29%

(Rollerson, Beese,Smith and Peters 2005)

Windthrow Monitoring Results Weyerhaeuser 2001- 2004

Final WordsGo Hawks