new density management in pacific northwest...

Density Management in Pacific Northwest forests

Should I thin?

• Is there an immediate cash flow or timber supply need?

• Do current and anticipated future stands meet management objectives (economic, wildlife, fire behavior, ecosystem services, . . . )?– Current stand and implications for future dynamics– Current dynamics (e.g., growth rate, mortality, value

accretion) and implications for future stand– Projected future stand– Landscape/ownership-level goals

• Do individual-tree dimensions (e.g., crown and H:D ratios) and stand-level attributes (e.g., relative density) maintain future silvicultural options?

Could thinning be at least a partial

solution?

Consider thinningConsider other options

(e.g., regenerate, let grow, etc.)

Yes

No

Yes

No

Are risks of possible adverse

effects acceptable?

Logging damage Soil compaction Invasive species

Should I thin?

• Intensity of thinning– Residual density relative to initial density– Reduction in SDI, SDIrel, RD, volume, basal area, tpa

• Type of thinning– From below– Proportional– From above; crown thinning– Selection thinning– Free thinning

• Tree selection criteria– Size– Spatial position– Species– Form/defect

Thinning Decision Points

Thinning Decision Points

Residual stand density

How to thin ?

How much ?

Initial StandSDI, SDIRELCrown ratio, H/Dbf/acsize class dist’nspecies composition

Thinning typed/D

What size classes ?

Residual composition

What species ?

Residual stand

SDI, SDIRELbf/acsize class dist’nspecies composition

Target Stand

SDI, SDIRELCrown ratio, H/Dbf/acsize class dist’nspecies composition

Thinning to meet immediate cash flow need

• Determine revenue/ac or volume/ac objective– If objective stated as revenue/ac then

• Estimate– Average hauling costs per MBF– Average logging costs per MBF– Average mill price per MBF

• Compute implied revenue per MBF– Revenue/MBF = mill price – logging costs – hauling costs

• Estimate MBF/ac required for revenue/ac target– Thinning MBF/ac = [target revenue/ac] / [revenue per MBF]

• Choose thinning specifications– Estimate size class distribution of removed trees and/or logs – Estimate number and average dbh of removed trees– Estimate thinning intensity

• Current and residual relative density, SDIrel or RDrel

• Reconsider revenue or volume objective if– Reduction from current SDIrel would exceed 20% or– Residual SDIrelwould drop below 25%

• Verify costs and revenues for thinning specifications– If necessary, adjust logging costs per MBF, based on size

class distribution of removed trees– If necessary, adjust delivered log price per MBF, based

on size class distribution of removed trees• If necessary, re-estimate MBF/ac required to meet

revenue or volume target• Reconsider revenue objective, volume objective, or

type of thinning if– Reduction from initial SDIrel would exceed 20% or– Residual SDIrelwould drop below 25%


600

600

330210

20% reduction in

SDIrel

Maximum SDI ~ 60055% SDIrel ~ 33035% SDIrel ~ 210

Estimatetarget volumeto be removed

Stand data

Logging costs Hauling costs

Log prices

CurrentSDIREL < 40% ?

Thinning not recommended

NO

YES

Compute current volume, SDI and SDIrel

Cash flow or timber volume

objectives



Residual SDIREL > 25% ?

Reconsider revenueor volume objective

Estimate residual SDI andresidual SDIrel

NO

Estimate number and mean dbh of thinned trees


Reduction in SDIREL ≤ 20% ?

YES

NO


Reconsider revenueor volume objective

YES NO

Compute net revenue from specified thinning

Cash flow target achievable?

Adjust objectives or thinning

specifications

Thin according to specifications

YES


Reduction in SDIREL ≤ 20% ?

Estimatetarget volumeto be removed

YES

NO

Logging costs Hauling costs

Log prices


Reconsider revenue

or volume objective

Reconsider revenue

or volume objective

YESNO

Compute net revenue from specified thinning

Estimate residual SDI andresidual SDIrel

NO

Cash flow or timber volume

objectives

Estimate number and mean dbh

of thinned trees

Cash flow target achievable?

Adjust objectives or thinning specifications

Thin according to specifications

YES

Thinning to achieve target stand or sequence of target stands

• Definition of target stand structure– Economic value

• Cash flow• Optimal net present value (NPV) • Desired tree size or log size distribution• Costs and revenues

– Volume per ac

– Average log size– Log prices

– Harvesting and hauling costs

• Multi-stand harvest schedule


• Definition of target stand structure (cont’d)– Wildlife habitat

• Late seral structure (size, density, spatial distribution)• Vertical complexity (vertical spatial distribution)• Horizontal structure (stand density, spatial variability)• Overstory-understory links (production, species

composition)

– Aesthetics– Potential fire behavior

• Crown and canopy bulk density• Tree/crown spacing• Height to crown base• Litterfall regime


• Definition of target stand structure (cont’d)– Hydrologic properties (interception, throughfall,

stem flow, evapotranspiration)• Canopy cover• Leaf area index• Crown mass and surface area

– Multi-objectives• Stand silvicultural regime or • Forest harvest schedule


• Assessment of current stand structure– Stand density (SDI, SDIrel, RD, RDrel, basal area, tpa)– Crown ratio– Height:dbh ratio (inches:inches, ft:ft, cm:cm, m:m)– Degree of differentiation

• Diameter distribution• Height distribution/vertical stratification

– Species composition• Relative abundance• Vertical differentiation (stratification) by species• Horizontal differentiation by species

• Assessment of current stand dynamics– Net and gross growth (basal area, volume)– Mortality rate– Differentiation

Thinning to achieve target stand structure

Currentstand

Residualstand

Residualstand

Residualstand

Targetstand

Targetstand

Targetstand

Structure Log distribution Value Habitat

Alternative developmental pathways for managed stand

Stand age

NOW FUTURE


TARGET

CURRENT


NO THINNING


Can’t get to target stand

Possible routes to target stand

Need to thin by

start of 4th growth

period


NO THINNING

TARGET

Need to thin by

start of 2nd

growth period

Assessing current stand dynamics as diagnostic criteria for thinning

Gross growthNet growthMortality

Stand data

Compute growth

components

Assessing current stand dynamics as diagnostic criteria for thinning

Thinning probably not a solution

Gross growth< 800 bf/ac/yr ?

YES

NO

YES

Net PAI< 800 bf/ac/yr ?

NO Mortality > 2% of gross PAI ?

Thinning not urgently needed

NO

Thin to recover mortality

YES

Parameters based on target stand structure:

- Net growth expectation (800 bf/ac/yr)

- Acceptable mortality rate (2%)

Thinning to maintain future options

Stand data

SDISDIREL

Crown ratioH/Dbf/ac

Compute diagnostic criteria


No thinning

SDIREL > 65% ?

SDIREL > 55% ?

>20 yrs to end of rotation ?

YES

NO

NO

YES CR>25% ?or

H/D<90 ?

NO

No thinning

YES >5 MBF/acif thin from

below to 55% SDIrel?

NO

Thin from below to

SDIrel=55%

No thinning

NO

YES

No thinning

>15 yrs to end of rotation ?

YES CR>35% ?or

H/D<70 ?

NO

No thinning

YES >5 MBF/acif thin from


NO

Thin from below or

proportional to SDIrel=35%

No thinning

NO

YES


SDIREL > 45% ?

NO

Structural objective

requires lower SDIrel ?

No thinning

NO

YES CR>35%or

H/D<70 ?

No thinning

YES >5 MBF/ac if thin from


NO

Thin from below or


No thinning

NO

YES

SDIREL > 35% ?

NO

Structural objective

requires lower SDIrel ?

No thinning

NO

YES CR>35%or

H/D<70 ?

No thinning

YES >5 MBF/ac if thin from


NO

Thin from below or


No thinning

NO

YES

Thinning not

recommended

YES

Primary structural/aesthetic objective is to grow late seral structure out to 100 years.

What general thinning strategy would provide the greatest economic return ?

Thinning to meet complex objective

Douglas-fir Levels-of-growing-stock Study

Hoskins installation

Established in 1963 in naturally regenerated stand

13 years breast height age, 20 yrs total age

Site index 134 ft at 50 yrs

Management objective to grow late seral structure to 100 yrs

Trends in SDI over time on Hoskins LOGS plots: Eight different thinning regimes + unthinned control

Marshall and Curtis 2002

Hoskins control plot in 1963, 80 crop trees per ac

Thinned plot 1969, control plot in background

Thinned plot 1969

Light thinning

1963

19661976

1966

Heavy thinning

1963

1976

1976

1976 Light thinning

1976 Heavy thinning

Start with 1979 data from Treatment 5

36 years total age

SDI 275, 53% of maximum (520)

193 tpa, 164 ft2/ac, 5344 ft3/ac

20.1 MBF/ac

Top height 89 ft

Mean crown ratio 40%

Mean H/D 85 (59-133)

Simulate stand dynamics to age 100

Initial diameter distribution

0

10

20

30

40

50

60

5 7 9 11 13 15 17

Dbh class midpoint (inches)

Tre

es/a

c

5 7 9 11 13 15 17

DBH class midpoint (inches)

TP

A

Trends in SDI over time on Hoskins LOGS plots: Eight different thinning regimes + unthinned control

Marshall and Curtis 2002

Should I thin?

• Is there an immediate cash flow or timber supply need?

• Do current and anticipated future stands meet management objectives (economic, wildlife, fire behavior, ecosystem services, . . . )?– Current stand and implications for future dynamics– Current dynamics (e.g., growth rate, mortality, value

accretion) and implications for future stand– Projected future stand– Landscape/ownership-level goals

• Do individual-tree dimensions (e.g., crown and H:D ratios) and stand-level attributes (e.g., relative density) maintain future silvicultural options?

Could thinning be at least a partial

solution?

Consider thinningConsider other options

(e.g., regenerate, let grow, etc.)

Yes

No

Yes

No

Are risks of possible adverse

effects acceptable?

Logging damage Soil compaction Invasive species

Should I thin?

Three thinning regimes

1 Control: No thinning

2 One thinning: Proportional thinning to relative SDI of 35% at year 36

3 Three thinnings: Proportional thinning relative SDI of 35% at years 36, 56, and 76

What will thinning buy us ?

1 Maintain tree/stand vigor to later ages

2 Acclerate growth of residual trees and approach to late seral structure

3 Provide some earlier cash return to improve net present value

Approaches ?

1 Optimization if we can quantify the objective (objective function) and specify constraints (structural objectives)

2 Prescribe, simulate, assess; prescribe, simulate, assess.

3 Simulate a set of alternative regimes, then assess by diagnostic criteria

0

50

100

150

200

250

300

350

400

450

500

0 20 40 60 80 100 120

Stand age (yrs)

Sta

nd D

ensi

ty I

ndex

No thinning

1 thinning

3 thinnings

Three thinning regimes

5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35

0

5

10

15

20

25

30

Trees/ac


3 thinnings

1 thinning

no thinning

Control

Three thinnings

Simulate stand dynamics to age 100

96112H40/Dq

22.119.4Dq

177181H40

22%18%Crown ratio

164307Basal area

62150TPA

220 (42%)434 (83%)SDI

3 thinningsUnthinnedAttribute

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

0 20 40 60 80 100 120

Stand age (yrs)

Scr

ibne

r vo

lum

e (b

f)No thinning

1 thinning

3 thinnings

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

0 20 40 60 80 100 120

Stand age (yrs)

Scr

ibne

r vo

lum

e (b

f)Standing

Standing +mortality

No thinning

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

0 20 40 60 80 100 120

Stand age (yrs)

Scr

ibne

r vo

lum

e (b

f)Standing

Standing+cut

Standing+cut+mortality

One thinning

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

0 20 40 60 80 100 120

Stand age (yrs)

Scr

ibne

r vo

lum

e (b

f)Unthinned standing volume

Thinned standing volume

Thinned standing + cut volume

Unthinned vs. one thinning

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

0 20 40 60 80 100 120

Stand age (yrs)

Scr

ibne

r vo

lum

e (b

f)

No thinning

1 thinning

3 thinnings

Standing live volume

5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35

0

5

10

15

20

25

30

Trees/ac


3 thinnings

1 thinning

no thinning

Control

Three thinnings

7 9 11 13 15 17 19 21 23 25 27

0

50

100

150

200

250

300

350

Logs/ac

Scaling diameter class midpoint (inches)

no thinning

1 thinning

3 thinnings

Control Three thinnings

Thinning costs and revenues

Interest rate 0.06

36 56 76 96

Log price ($/MBF) 500 550 600 650Clearcut logging cost, cable ($/MBF) 200 175 150 125Thinning logging cost, cable ($/MBF) 250 225 200 175Clearcut logging cost, ground ($/MBF) 90 85 80 75Thinning logging cost, ground ($/MBF) 100 95 90 85Hauling cost ($/MBF) 50 50 50 50

Net present value of three stand density regimes

Cost/revenueYear

Fixed logging costs and log prices

Fixed logging costs and increasing log prices

Declining logging costs / increasing log prices

Earlier Hoskins LOGS plots

Start with 1966 data from Treatment 5

23 years total age


365 tpa, 86 ft2/ac, 1468 ft3/ac

1.5 MBF/ac

Top height 49 ft

Mean crown ratio 76%

Mean H/D 80 (54-80)

Primary objective is to maximize revenue from growing timber.

What is the optimal thinning regime, or should you thin at all ?


Initial diameter distribution

0

20

40

60

80

100

120

140

160

180

200

3 5 7 9 11


Tre

es/a

c

3 5 7 9 11

DBH class midpoint (inches)

TP

A

600600

330210 Maximum SDI ~ 600

55% SDIrel ~ 33035% SDIrel ~ 210

23 yrs in 1966

36 yrs in 1979

No thinning after calibration thinning in 1966

0

50

100

150

200

250

300

350

400

450

500

0 20 40 60 80 100 120

Stand age (yrs)

Sta

nd D

ensi

ty I

ndex

No thinning after 1979

1 thinning

3 thinningsNo thinning after 1966

No thinning after calibration thinning in 1966

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

0 20 40 60 80 100 120

Stand age (yrs)

Scr

ibne

r vo

lum

e (b

f)


1 thinning

3 thinnings


What approach would you use to identify the optimal thinning regime, or for deciding whether thinning pays ?


Assume you have YOUR optimal thinning regime identified.

Would you monitor stand development?

If so, what would your monitoring plan look like?


Stand density and fuel accumulation

Could you design a stand density regime to control fuel accumulation?

To what degree does stand density regime control fuel accumulation?

Stand density and fuel accumulation

Ponderosa pine spacing trials

• Lookout Mountain

• 6-, 12-, and 18-ft initial spacings

• Start with plantation at 13 years total age

• Simulate stand development for 100 years

Average diameter of dead branches (cm)

0 20 40 60 80 100

Dea

d br

anch

dia

met

er (

cm)

0

10

20

30

40

50

Stand age (years)

6-ft

Three initial spacings

18-ft

12-ft

Branch mortality (number/ha/yr)P

erio

dic

annu

al b

ranc

h m

orta

lity

(no

ha-1

yr-1

)

0

5000

10000

15000

20000

25000Lookout Mountain

20 40 60 80 100

Stand age (years)

6-ft


18-ft

12-ft

Branch mortality (necromass/ha/yr)P

erio

dic

annu

al b

ranc

h m

orta

lity

(kg

ha-1

yr-1

)

0

200

400

600

800

1000

1200

1400

1600

20 40 60 80 100

Stand age (years)

6-ft


18-ft

12-ft

Site effects on branch mortality (necromass/ha/yr)

Per

iodi

c an

nual

bra

nch

mor

talit

y (k

g ha

-1yr

-1)

0

200

400

600

800

1000

1200

1400

20 40 60 80 100

Stand age (years)

6-ft

18-ft

12-ft

Lookout Mountain

Pringle Butte

Site index 55 vs. 85 at 50 yrs

Black Rock Plot 31 – Crop tree thinning

Stand history

Naturally regenerated after logging near turn of the century

48 years total age in 1957

Thinned in 1957 from 294 to 51 trees/ac

Underplanted in 1959 with western hemlock at 6-ft spacing

Black Rock Plot 31 – Crop tree thinning

Initial stand attributes

48 years total age in 1957


294 tpa, 229 ft2/ac, 10,346 ft3/ac

39.2 MBF/ac

Black Rock Thinning Trials

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44

heavy t hinning

cont rol

0

5

10

15

20

25

30

Tpa

Dbh class midpoint (in)

Black Rock thinning plots (rep 2), 1995

heavy thinning

medium thinning

light thinning

control

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44

crop52

0

5

10

15

20

25

30

Tpa

Dbh midpoint (in)


crop52

crop42

control



0

50

100

150

200

250

300

350

400

control light medium heavy crop

Treatment

Tpa

or

basa

l are

a (f

t2/a

c)

0

5

10

15

20

25

30

35

Dq

(in)

Tpa

Basal area

Dq



Black Rock thinning plots (rep 2), net PAI for 1990-2003

-50

0

50

100

150

200

250


Treatment

PA

I as

% o

f con

trol

Cubic

Scribner

150 ft3/ac/

yr

685 bf/ac/

yr

163

264

1459

268

1309

757

-41

-7



0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000


Treatment

Cub

ic v

olum

e (f

t3/a

c)

mortality

thinned

standing


2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44

crop tree

0

10

20

30

40

50

60

70

Tpa

Dbh midpoint (in)


crop tree

control


Overstory SDI 274 (53% of 520)

Understory SDI 35 (4% of 850)

Understory response to thinning

Carrying capacityTree growth Microclimate Physiology Summary

Thinning

Understory vegetation is happy to use resources that are not captured by trees !

Crop tree thinning & hemlock understory, 1985


1985

Crop tree thinning

Hemlock understory

new density management in pacific northwest...

Documents