Silviculture Based on Natural
Disturbances: Critical Reflections
on Its Status and Future in the
Northeastern United States
Robert S. Seymour and Alan S. White
5th North American Forest Ecology
Workshop
June 14, 2005
Outline
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Definition
Natural disturbance dynamics: brief review
Status by Ownership
Obstacles
Simple Application Principles
Personal Observations
My definition of
“natural
disturbance
paradigm” =
“Ecological
Forestry”
(Seymour and
Hunter 1999)
Ecological Forestry defined
“Using knowledge of natural disturbance
regimes and ecological processes to
make management decisions about …”
• Stand structure (vertical and horizontal)
• Rotations and cutting cycles
• Species composition
• Regeneration methods
• Other biodiversity issues
Don’t let “The Perfect” be the
enemy of the “Good Enough!”
• Ecological mimicry is a downright threatening
concept to production foresters challenged to
produce value and commodities
– They “tune out” in advance, because they know
they cannot do this any where near perfectly
• About 1996, I stopped using “….emulating or
mimicking natural disturbance regimes…..”
and substituted “…learning from nature…” as
the operative concept
Landscape-level Thinking,
Maine ca. 1992: the TRIAD
Triad: Origin and Acceptance
(ca. 1990-1995)
• Attempt to resolve seemingly irreconcilable
conflict in Maine between:
– Essentially no system of ecological reserves,
– Predicted timber supply shortfalls
• Everybody endorsed 2/3 of the Triad
• Proved to be a great device for:
– Legitimizing everyone’s agenda
– Exposing everyone’s biases
Recent Evolution of “Balanced Forestry”
• In 1992, most people (but not me) said the
“reserves” would be the hardest part
• Over a decade later, we have ecologically
designed (though arguably inadequate)
reserve systems in many places
• The management of “The Matrix” under
dominant ecological principles – the
silviculture -- has proven the be the real
bottleneck (and focus of the rest of this
presentation).
Ecology of Northeastern Forests:
Gap Dynamics rule
• Natural disturbance
regimes dominated by
partial disturbances
(some minor
exceptions), long-lived
shade-tolerant species
• Stand-replacing
disturbances were rare
Estimated return intervals (years) of standreplacing disturbances in the northeastern
US (Lorimer and White 2003)
Disturbance
Agent
Northern
Hardwoods
SpruceHardwoods
Sprucedominated
Flats
Firdominated
Conifers
Fire
1000-3000
385-1200
800
-
Wind
1000-2500
575-1000
285
-
Spruce
Budworm
NSR
NSR
NSR
80-100+
Combined
500-1364
230-545
210
?
What silvicultural systems do these
dynamics imply?
• Multi-aged stand structures, with a significant
component of “old” trees
• Regeneration in gaps or patches within
irregular stands
• Single-cohort (even-aged) silviculture –where entire stands are regenerated in single
cuttings -- would be the distinct exception
(< 20% of the landscape under age 100)
• This is the bottleneck!
Status of Ecological Forestry (based
on silviculture applied)
• Large Private ownerships (not under
conservation easement or FSC
certified): rare to non-existent.
• Practices range from traditional
shelterwood (with prompt overstory
removal and little retention), to heavy
exploitative cuttings from above with no
silvicultural intent.
Northern hardwood shelterwood on
FSC certified private owner
Status of Ecological Forestry
(based on silviculture applied)
• Public Lands (and some FSC certified
private and NGO lands): Ecological
forestry is more common, but the
degree of “emulation” depends on forest
type and land-use history
Status of Ecological Forestry
(based on silviculture applied)
• Case 1: Acadian region (northern hardwoodspruce-fir types)
– Northern New England, New Brunswick, Nova
Scotia never cleared for agriculture
• Species composition altered somewhat, but
largely intact
• Challenge is to restore diversity in age
structure, esp. enhancing late successional
stages
Group selection cutting – red spruce mixedwood,
Baxter Park Scientific Forest Management Area
.02-.04 ha gaps, 1/14 of the stand on
10 year cutting cycle
Status of Ecological Forestry
(based on silviculture applied)
• Case 2: Central Hardwoods, Allegheny
Hardwoods, Lakes States aspen
• Species composition highly altered from
presettlement due to land clearing, repeated
heavy cutting, wildfires.
• Present even-aged forest of early to midsuccessional species (red oak, black cherry,
white pine, aspen) is commercially valuable
Case 2: Central Hardwoods, Allegheny
Hardwoods, Lakes States aspen
(continued)
• Enlightened silviculture aims to perpetuate
present forest via two-aged systems
(shelterwood with reserves)
• In many cases, restoration of presettlement
composition or structure not feasible,
especially where deer populations are
excessive (prevents gap regeneration, both
in nature and under management).
Mature even-aged black cherry
on Pennsylvania State Forest
2003 Timber sale = $8
million on 200 acres.
Shelterwood incomplete removal cutting on
Massachusetts Wildlife Lands
Oak and pine reserve trees
Group shelterwood (oak-pine) MDC
Lands (Massachusetts)
Gaps = .1 to 1 ha, 1/3 of the stand on
30-year cutting cycle
Status (summary)
• Modest developments, mostly on public
forests and a few FSC-certified family
ownerships (< 20% of forest area)
• Many 1990s initiatives on industrial
lands have since been abandoned after
ownership changes to shorter-term
investors
What are the obstacles?
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•
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The Science?
The System?
The Resource?
The Profession itself?
Political and Stakeholder Support?
What about “The Science”
Conservation biology
enters mainstream
forestry (1990)
“Applications” are
documented in books
(2004)
Scientific Progress
• Since 1990, significant studies in
disturbance ecology have led to useful,
quantitative working hypotheses for most
common forest types
– Disturbance rates
– Patch sizes (regenerated)
– Structure
• Scientists have “rallied” – they’re largely not
the cause for limited application
Simple Principles for Application
(this is not rocket science!)
• Must regenerate new cohorts at a disciplined
rate, keeping the matrix intact
• Guiding stand structure is based on AREA
not size (e.g., dbh distribution)
– Focuses directly on the dynamics, not static
conditions
• Must also retain legacies (trees, patches) to
restore late-successional characteristics
– This is where structural goals are important
Natural Variation in Disturbances
(based on ca. 20 studies; Seymour et al 2002)
Contiguous Area Disturbed and Regenerated - ha
10000
1000
100
100-year return
interval
10
Severe
Fire
and
Wind
1
0.1
0.01
0.001
0.0001
1
Range =
.001 - .1 ha
Natural
Canopy
Gaps
100
1000
10000
Interval between Disturbances (at the same point on the landscape) - years
Clearcutting on a 100-year rotation?
Contiguous Area Disturbed and Regenerated - ha
10000
1000
100
10
Severe
Fire
and
Wind
Severe
Fire
and
Wind
1
0.1
0.01
Natural
Canopy
Gaps
0.001
0.0001
1
100
1000
10000
Interval between Disturbances (at the same point on the landscape) - years
10% per decade, or
1% per year
Where do we turn for
guidance? A
Disturbance
Chronology
• Canopy turnover
by decade (for 6
forest types in an
old-growth reserve,
northern Maine;
Fraver 2004)
Formulating ecologically based
silvicultural systems: regeneration rate
1. Forget the usual constraints of classical
group selection systems (equal cutting
cycles and balanced age structure) -Nature is not this regular!
• The “1% rule”: Within the stand, area
regenerated at each harvest should fall
within natural disturbance boundaries
–
avg. = 10% per decade (range = 0-30%)
Managed
stand =
100 yrs
Comparison to
unharvested
old-growth
• Old-growth forests
not balanced but
bimodal, with “tail”
of legacy trees
Age structures oldgrowth red spruce
stands (Fraver 2004)
Old-growth legacy
(100-300 yrs)
Formulating ecologically based
silvicultural systems: patch size
2. Spatial arrangement of areas
regenerated should also fall within
natural limits
– patch size = .01- 0.1 ha <<< stand size
– Larger patches depart from the “natural”
(but are still preferable to stand-wide
uniform treatments)
– Think in terms of fewer, larger stands with
more within-stand diversity
Formulating ecologically based
silvicultural systems: stand tending
3. Thin the matrix opportunistically, to:
 Presalvage short-lived species (aspen, fir,
paper birch)
 Release crop trees of long-lived species
BUT
 Make sure not to “over-regenerate” the
stand as a whole, or harvest future legacy
trees (resist uniform shelterwood).
 May be possible to do only once (first
entry).
Formulating ecologically based
silvicultural systems: biological legacy
4. Designate permanent reserve trees as
a biological legacy in gaps as they are
treated
 Maintains and restores late-successional
conditions as regenerating groups enter
stem exclusion
What do we call this?
• Combine the traditional advantages of
uniform shelterwood with the ecological
advantages of group selection
• Apply shelterwood with reserves, but in
small patches within stands
– Entire stand contains examples of all stages of the
regeneration process
– Age structure within stands varies spatially, not
temporally
• = “Group Shelterwood (with reserves)”
Irregular (group)
Shelterwood =
Femelschlag
Swiss Femelschlag
1928
Bavarian Femelschlag
U. Maine Forest Ecosystem Research Program
(FERP) – begun 1994
Bob Wagner, Front
Page of Bangor
Daily News
U. Maine Forest Ecosystem
Research Program:
The “Acadian Femelschlag”
• Expanding gap system based on three ecological
parameters:
 1% Annual Disturbance Frequency (20% per decade for
5 decades, then no regeneration for 50 years)
 Initial gap sizes average 0.1 - 0.2 ha (expanded on 10year cutting cycle)
 10% permanent structural retention, dispersed
throughout the entire stand
• North American Translation: Irregular group
shelterwood with reserves
Initial Groups
Age Distributions of Final Regeneration Harvest
Age of Regenerated Stand
Year of Harvest
40
30
20
10
0
1995
2005
2015
2025
2035
Skid trail
200 m
Entry #1
Expanding Gaps - 10 years
Age Distributions of Final Regeneration Harvest
Age of Regenerated Stand
Year of Harvest
40
30
20
10
0
1995
2005
2015
2025
2035
Skid trail
200 m
Entry #2
Expanding Gaps – 20 years
Age Distributions of Final Regeneration Harvest
Age of Regenerated Stand
Year of Harvest
40
30
20
10
0
1995
2005
2015
2025
2035
Skid trail
200 m
Entry #3
Expanding Gaps – 30 Years
Age Distributions of Final Regeneration Harvest
Age of Regenerated Stand
Year of Harvest
40
30
20
10
0
1995
2005
2015
2025
2035
Skid trail
200 m
Entry #4
Expanding Gaps – 40 years (Last)
Age Distributions of Final Regeneration Harvest
Age of Regenerated Stand
Year of Harvest
40
30
20
10
0
1995
2005
2015
2025
2035
Skid trail
200 m
Entry #5
Expanding Gap Profile (Acadian Femelschlag)
First harvest
(1995)
Third harvest
(2015)
Fifth harvest
(2035) the next
50 years.
Gap, 7 years after initial entry
Hemlock
legacy tree
Obstacles: The Resource?
•
The challenge is RESTORATION, not maintenance
– Most forests are now much younger and more even-aged
than naturally
•
Two Goals (both require PATIENCE!)
1. Re-create, on cutting at time, a forest dominated by multiaged stands, some with strong late-successional features
2. Gradually rebuild stocking of long-lived, shade-tolerant (and
valuable) species
•
The problem is more complex than simply mitigating
clearcuts or making single-cohort silviculture more
biodiversity-friendly
Retention patches?
• Better than nothing, but not by much!
Mature MW Stand,
northwestern New
Brunswick
Obstacles: Institutional
• In the US, large industrial ownerships rapidly
changing hands to timber investment
companies
• Immediate expectation of non-sustainable,
double-digit rates of returns by short-term
investors
• Ecologically, many of these forests just need
a “rest”, yet many are only being cut harder
and more frequently
Obstacles: Professional
• Practicality: Even-aged silviculture has
tremendous appeal to overworked and
under-funded foresters, regardless of
how “unnatural” it may be, because it’s
SIMPLE and PREDICTABLE.
Things that are relatively easy
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•
•
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Buffering riparian zones, if mapped
Designating large patches to cut
Reserving large unmerchantable legacy trees
Leaving reserves in isolated small patches
(“islands”)
• Predicting future yields of even-aged stands
• Making “expedient” broad-brush even-aged
regeneration prescriptions
Things that are difficult
(but necessary)
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•
•
•
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Marking individual trees to cut or retain
Leaving dispersed reserve trees
Screening areas for rare things
Regenerating only 1% of the forest annually
Regenerating only 10-20% of a harvest
block
• Leaving significant areas of a harvest block
untreated
Things that are difficult (continued)
• Leaving merchantable trees to die
• Predicting future yields of complex,
mixed-species stands
• Taking the time -- and being
rewarded -- for making a thoughtful,
stand-specific, ecologically sensitive,
balanced, silvicultural prescription
that enhances diversity
Obstacles: Political and
Stakeholder Support
• Presently in the US, meaningful
application (= large-scale) must occur
voluntarily on private lands
– At best, regulations codify mediocrity, not
reward excellence.
– I see absolutely no prospect of enforcing
ecological forestry via regulations (except
perhaps for endangered species)
What about Green Certification?
• Rigorous, market-based certification (FSC,
not SFI) -- the reward for doing all those “hard
things” -- has failed to provide consumerdriven market incentives to “green up”
management on private lands.
• Certification has arguably made the “good”
even better, but has done little to force a
larger-scale paradigm shift toward a more
ecological forestry.
Personal Reflections on
Ecological Forestry
• Obstacles are no longer scientific, but science
alone does not provide a mandate!
• Disturbance ecology is no more or less
“scientific” than old-fashioned production ecology
that underlies plantation forestry
– Not necessarily in conflict, if balanced at the
landscape level
• Decision is really about human values: what do
we (society) really want to sustain, and where?
– Biodiversity
– Free enterprise
– Global competitiveness
Personal Reflections on
Ecological Forestry
• I had hoped the forestry profession would
embrace ecological forestry much more
widely, in hopes of becoming popular again
with people
• Unfortunately (for us) society has a doublestandard: we don’t like our forests treated
non-sustainably but we also want cheap
forest products
• Conclusion: practicing Ecological Forestry, at
present, is too costly, with no commensurate
economic benefits
The Ultimate Irony?
• The more the forest landscape is dominated
by commodity extraction, rather than longterm stewardship, the more public lands will
be pressured to keep areas reserved from
any cutting.
– This is where the big, old trees are.
• Will we eventually lose our finest examples of
long-term forestry in eastern North America
(to reserves) so we can continue to exploit
the rest under the doctrine of free enterprise?
The Ultimate Irony?
• The eventual consequence will be a global
BIAD (like New Zealand) where wood and
paper come from plantations somewhere else
while our region’s forests are reserved and
exploited opportunistically.
• Do environmental stakeholders really support
ecological forestry everywhere? Or are they
merely advocating that it replace production
forestry on private lands?
Who is the real constituency for
ecological forestry?
• If it’s viewed as an esoteric concept
understood and embraced by only a
small group of Type B foresters,
academics, and scientists, then it’s
doomed.
• We must find a way to articulate the
benefits, and society must find a way to
“pay” for it.
Will Ecological Forestry become
a Dead End?
• It depends.
• Maintaining and improving long-term
applications (via adaptive management) is
SO important here!
• Such benchmarks are arguably as, or more,
important than ecological reserves
• Do the best we can, whenever we have the
opportunity, and hope society will eventually
pay attention.