darwin’s forestry: is our profession advancing s forestry: is our profession advancing...

Darwin’s Forestry: Is our profession advancing scientifically?

Bob SeymourNE Annual Meeting Forest Guild Northwood, NHApril 24, 2009

David M. Smith•

“For forestry to survive, we must make it PAY.” (Ralph Hawley)

•

“For forestry to survive, we must make it SCIENTIFIC.” (Harold Lutz)

1921-2009

Topics1.

Crop-tree Silviculture and the use of Stocking Guides for silvicultural prescription

2. Ecological Forestry based on natural disturbance dynamics

3. Carbon: the next valuable forest product?

4.

Third-party Certification

1960s: Forest Service silviculturists codify even-aged silviculture into

cookbook guidelines

Roach and Gingrich 1968

Marquis et al 1980s

Original WP Stocking Guide (1973)

Langsaeter

Hypothesis: Constant growth over range of density (original basis of SG, Gingrich 1967, also Smith 1962)

B Line

A Line

Issues

•

Is Langsaeter

universally valid?•

Even if it was, what about other mangement

objectives?

Other Pine Management Objectives?

• Maximum Value•• Maximum Carbon

Does B-line thinning meet these goals?

•

Pruned lower bole (17-26 feet)•

Live branches above this (no black knotted logs)

•

No crown recession after first thinning

•

30-50 trees per acre (“crop- tree” or “low-density

management”)

Crop-tree WP Silviculture

Low-density schedule on Revised Stocking Guide

Crop-tree growth (upper crown classes)

15-year changes in (dominants and codominants only):

Treatment

Change in

Crown Length (feet)

Change in Live Crown Ratio

Height to crown base

(lowest living

branch, feet)

Dbh (inches)

Volume per Tree (cubic

feet)

B Line 6.40 .023 8.6 2.2 (1.5x) 9.1 (1.2x)

Low-Density 11.79 .099 3.1 3.7 (2.5x) 15.1 (2.0x)

Unthinned Control 3.85 -.023 10.9 1.5 7.4

Stand growth

15-year stand volume growth (ft3 per acre per year)

Treatment Gross Mortality Net

B Line 102.5 14.1 88.4

Low-Density 92.6 2.8 89.8

Unthinned Control 167.6 36.1 131.4

Growth vs. Density (4 measures)

•

No Langsaeter Plateau or

Optimum! (B line is irrelevant)

•

No downside to low-density silviculture: Bigger trees, same total yield as B-line

B-line seems to be a bad compromise for either objective

$$$

Recent Crop-tree Thinning (Univ. Maine Demeritt

Forest)

•

BA = 180•

QMD = 6”

•

Age = 35•

Height = 40-50 ft

•

Crown base = 22-30 feet

•

Ht:Dbh

= 94 (!)

Residual Stand

•

93 trees per acre•

22 ft spacing

•

BA = 26 ft2 (!)•

88% Removal

Crown closure

A Bonus Resurrection: Just use Wilson’s spacing fraction?

(spacing:height ratio)

•

Thin when spacing fraction = about 40% of dominant height, to a value of 50% or a little higher in young stands (under 50 feet tall).

Proper Role of Stocking Guides?•

Main value is to DEscribe

stand density and

perhaps crown closure.•

Do NOT use a stocking guide, or the lines thereon, to PREscribe

ANYTHING!

Thinning to the B line is not automatically good, and will effectively preclude high-

value crop-tree silviculture•

Would be better replaced by density management diagrams (Reineke, -3/2 Self-

thinning) for thinning prescriptions in pure conifer stands.

How can I predict the outcome of prescriptions?

II. Practicing Ecological Forestry based on Natural Disturbance Dynamics

•

What was or is “Natural”?•

How do we define our target stand structure?

•

Do we need “new” silvicultural systems?

SAF Task SAF Task Force (1993)Force (1993)

•

Very controversial•

Ultimately never endorsed nationally

•

NESAF only local society to do so

•

One reason we have the Forest Guild today

Ecological Forestry – What is “Natural?”

•

Since ca.1990, significant studies in disturbance ecology have led to useful, quantitative working hypotheses for most common forest types–

Disturbance rates

–

Patch sizes –

Post-disturbance Legacies

Ecology of Northeastern Forests: Gap Dynamics rule

•

Disturbance regimes dominated by partial disturbances (some minor exceptions), long-lived shade-

tolerant species•

Stand-replacing disturbances and thus, even-

aged stands,

were very rare

What silvicultural systems do these dynamics imply?

•

Multi-aged stand structures, with a significant component of “old” trees

•

Regeneration in small 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)(< 5% in sapling size class)

Real-world Challenge: Restoration, not Maintenance

•

Most stands have history of heavy cutting at some point, and are thus single-

or two-cohort structures

•

How do we gradually add back age diversity?

•

What is our Target Stand Structure?

Possible Conversion Pathways (assuming

regular cutting cycle and a

goal of a balanced age

structure; Nyland 2003)

Uniform Gap

The “Target Structure” –

Option 1: A tree size

(dbh) structure

Reverse-J DBH Distribution

From Nyland (1996)

•

Descriptive perhaps, but not informative

•

H. A. Meyer (1952)•

De Liocourt

(1898)

•

“B-D-q” Method (Leak 1964)

History –

Dbh Structure

Hawley and Smith (1954)

The “Target Structure” –

Option 2: an area-based

structure

Disturbance Chronology (Fraver, White, Seymour 2009)

Area by Cohort (decade of initiation)

10% per decade for 180 years, or 1%

per year !

Formulating ecologically based silvicultural systems: regeneration rate

1. The “1% rule”: Within the stand, area regenerated at each harvest should fall within natural disturbance boundaries

– For a balanced system, portion of stand regenerated = cutting cycle (in percent)

– Eg: 10% per decade, 20% every 20 years, etc.

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: biological

legacy

3. 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 exclusion10% of original stand (15 ft2/ ac), focusing on larger trees of late-successional, long-lived species

Formulating ecologically based silvicultural systems: stand

tending4. Thin the intervening matrix along trails and

gap edges, to:Presalvage short-lived species Release crop trees of long-lived speciesEliminate undesirable seed sources

BUTMake 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).

What do we call this?

• Apply shelterwood with reserves, but in patches within stands√ Entire stand contains examples of all

stages of the regeneration process√ Age structure within stands varies spatially,

not temporally

Swiss Femelschlag Bavarian Femelschlag

Irregular (group) Shelterwood

=

Femelschlag 1928

•

Americans selectively imported German systems…somehow, we forgot this one!

2008

Large Gaps (5 cohorts) Small Gap (10 cohorts)

Harvest progression = light to dark

Group selectionIrregular group shelterwood

The “Acadian Femelschlag” (ca. 1994)

Actual Map of AFERP RAs 1,2

Large Gap after second entry (partial overstory removal) with final reserve trees

Large Gap after second entry (partial overstory removal) with final reserve trees

Untreated Matrix, looking into 14-year-old gap and 4-year-old expansion

Tall regen. from first

entry

Overstory removal in first expansion zone (year 11)

Narrow extraction

trail at boundary

Reserve Trees

• Reserve trees that die or are harvested can be periodically replaced

• Criteria for selection:– Current or potential wildlife

trees– Uncommon species – Potential high timber value

under a long rotation (e.g., white pine)

One tree “IN” with 15 BAF

Prism Everywhere in

Gap

Advantages of Area-based Structures --

Ecological

1.

Manages regeneration deliberately, not by assumption (of future ingrowth)--

Gap size, overall regeneration rate

2.

Ecological sustainability guaranteed (if cutting cycle is comparable to natural disturbance rates)

3.

No need to assume a problematic linkage between age and size

All of these are demonstrated Achilles’ Heels of B-d-q

structural approach!

Advantages of Area-based Structures --

Operational

4.

Pre-harvest layout, designation of reserve trees, logging, early tending are all concentrated on 10-30% of stand--

No need to work throughout entire stand (after first entry)

5.

No need for pre-harvest dbh distribution information, or overall marking tally

6.

Yields are more straightforward to predict7.

Light harvests (<25%) are feasible (really = “mini clearcuts”)

What about uniform shelterwood?

May retain or restore species, but will notrestore diverse age structure

Retention patches?

Mature MW Stand, northwestern New

Brunswick

Better than nothing, but not by much!

Shifting Mosaic?

•OK in boreal, but here it’s a totally artificial landscape in New England

After second harvest (= first large-gap expansion)

Year 11

Small sub-stand patches (gaps) with retention?

Personal Reflections on Ecological Forestry

•

Obstacles are largely NOT 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 (Triad Zoning)

“The Forest Doesn’t Give a Damn” – Jerry Franklin

• Decision is really about human values: what do we (society) really want to sustain, and where?

• We don’t need any new (aka “variable retention”, etc) systems, just more creative application of uncommon ones.

III. Carbon

and Climate

–

the inconvenient concept of

Additionality

Recent Maine Initiative

Aboveground Tree (Live + Dead) Biomass vs. Stand Age (Adirondacks)

y = 82.78Ln(x) -

219.83R2 = 0.63

0

50

100

150

200

250

300

350

400

0 100 200 300 400 500Dominant Tree Age (yrs)

Abo

vegr

ound

Tre

e B

iom

ass

(Mg/

ha)

Keeton et al. 2007. Ecological Applications

•

Virtually all forests are net C fixers (519 studies, up to age 800)

Howland Experimental Forest: Mature Two-aged Spruce-fir

FVS Simulations,

using the Fire and

Fuels Extension

(David Ray

et al. in prep.) Carbon- Forest & Stored

2000 2020 2040 2060 2080 2100

Car

bon

(tons

/ac)

0

20

40

60

80

Merchantable Volume

Mer

ch v

ol (c

ds/a

c)

0

10

20

30

40

Basal Area

Bas

al a

rea

(ft2 /a

c)

0

50

100

150

200

250

ControlPartial-cutShelter-100 yrShelter-60 yr

Maximum Carbon storage = NO Management! (top line)

A Very Important and Influential Analysis!

(Chris Hennigar, UNB, 2008)

Hennigar

et al. (2008)•

30,000 ha hypothetical mixed forest

•

Maximized various objectives:– Timber Harvest– Product Carbon– Forest Carbon– Forest + Product Carbon

•

Also considered product substitution benefits (wood for concrete, steel)

Hennigar

Results

Hennigar

Point 1:•

Ignoring substitution benefits, maximizing Forest Carbon is –

NOT a no-management scenario

–

Average rotation is 155 years (vs. 60 for Max AAC)

–

Stores 1.8 X C than MaxAAC, but–

Product harvest = only 31% of MaxAAC

•

THIS IS WHAT TRADITIONAL INDUSTRIES ARE (LEGITIMATELY) AFRAID OF!

Hennigar

Point 2:

•

Adding in Product Substitution Benefits changes things markedly: –

MaxAAC

C = 94% of Max Forest C

•

Thus, substitution assumptions are very important, and an active field of study and source of debate.

•

“Wood is Good”

Hennigar

Point 3:

•

Maximizing Forest and Product Carbon JOINTLY: – Stores 1.3 X C as Forest-only and

1.4 X C MaxAAC– Harvest is 51% of MaxAAC– Rotations are LONG (avg

= 120

years, shorter than than

the MaxForestC, but still twice that of MaxAAC).

Implications –

True Additionality

•

Annual differences (.091 T/ha) are small relative to total (80-100 T/ha) standing stocks

•

0.091 T of C = 0.334 T CO2

, or 3 ha needed to sequester one additional T.

•

This “costs” 1.45 m3

[0.6 cords = 257

BF] = $29/ha of annual product harvest.•

Storing one extra Ton of CO2

per year thus costs the landowner 3 ha x $29 = $87 per year. (Current price = $3/T)

Are shorter rotations better? (Perez-Garcia et al. 2005, often cited to support this point)

Hypothetical one-hectare stand, starting with bare land

Starting Conditions are IMPORTANT!

C stored in a maturing forest

These huge substitution benefits

would not favor shorter rotations in

real-world forest with all age classes

Carbon and Climate”Climate Change in New England” Recent

NESAF Policy Statement “Forest management on the New

England landscape is necessary to have a healthy forest with many age classes to enhance carbon sequestration.”

National SAF Policies stress the importance of “managed forests” without being specific.

Carbon and Climate

Guild Recommendations (p. 35 ) are fine, I particularly like the inclusion of the role of reserves.

Science thus suggests that: Optimum C strategy is:

•

Harvest moderately (well below max), keep high volumes of growing stock, but still enough to provide forest products that will effectively substitute for less-C-

friendly products (i.e., avoid leakage)•

This is arguably what some exemplary landowners are already doing, mainly for ecological reasons (Baxter SFMA)

•

But, the reality is that there’s no money in Carbon, at least presently.

Certification and Science

•

Worry about uneven application of the principles and criteria…Mass example

•

(Lack of) Retention•

Advance Regeneration

•

Early successional habitat•

Plantation liquidation

15-acre Norway spruce clearcut

•Whole-tree operation, all slash left piled at landing

•Very few reserve trees

7 yr old Norway Spruce Clearcut

Norway Spruce

seedling, thriving

70-yr-old White Pine plantation “shelterwood removal”

• No apparent attempt to regenerate pine

•Very few reserve trees, high damage to advance regeneration

Enriched NHw-Red Oak stand: 2-acre rectangular patch cut with no advance

regeneration, no retention, no large DWD

Clearcut with pitch pine reserves, 50- year-old pine plantation established

after 1950s wildfire

Old White Pine legacy tree (fire residual) marked to cut

Prescription to create “early successional” habitat

Justifications offered?•

“Eliminate exotics” (even though they offer valuable habitat that takes 50+ years to replace)

•

“Early successional habitat is growing scarcer”•

“Regenerating oak requires too much patience”

•

“Regeneration areas are easier to track and monitor”

•

“We have plenty of reserve trees on the landscape”

Thanks for inviting me!