Mark Coleman, Terry Shaw & Mark Kimsey

Establishment of the Paired-Plot Density

Management network: 2013-2018

Goal: Improving vigor and adding value to managed

forests of the diverse Inland Northwest landscape.

IFC Goal & Membership

Obvious need to test site-specific silvicultural options in the INW

Wie et al 2018

Categorize forest site quality throughout the Inland Northwest

• Define tree and stand responses to treatments across the range of forest site conditions

• First focused on site factors that define maximum stand density

• Density management creates lasting improvements to stand condition

Utility of Density Management

• Improves stand structure and development through density management

• Enhances resistance to fire, drought, pests & disease

Forgone or delayed thinning :

• Growth opportunity loss

• Extends rotation

• Increases mortality risk

Stand density relative to normal stands defines

thinning prescriptions for highest stand vigor

ln Density

ln D

iam

eter

100% - Normal60% - Eminent mortality35% - Lower Management Zone25% - Crown closure

Self-thinning

trajectory

Density Management Research

1. Carrying capacity analysis• Characterize maximum density across the INW

• Species specific

2. Spacing Trials• Validate maximum density models

• Compare growth response to thinning among site classes

• Determine how stand development affects thinning response

Kimsey et al 2019

Geospatial representation of maximum Stand Density Index

Maximum density frontier models

TopographyGeography

ClimateSoil

Density x Diameterdepends on:

Spacing Trials

• Identify how stage of stand development affects thinning response

• Measure thinning response across site productivity classes

• Compare among dominate species

Total stand productivity should reach a broad optimum following canopy closure

Growth phases:

I.No competition

II.Growth decline

III.Constant wide optimum

IV.Competition-caused decline

Langsaeter’s Curve

Δ𝐺

Δ𝐺𝑆=⇩

Δ𝐺

Δ𝐺𝑆= 0

Δ𝐺

Δ𝐺𝑆< 0

To plateau or not to plateau

• Uncertain width of plateau

• Uncertain effect of site quality

• Gross vs Net production

• Typically noisy data causes uncertainty

Sta

nd

Pro

du

ctivity

Relative Density

Moderate optimum

Continuous increase

0 25 50 75

Growing stock

Gro

wth

Loblolly pineBurkhart 2005

Broad optimum

Sta

nd

Pro

du

ctivity

Site ClassT

ree

Gro

wth

Site Class

No-thin

Thin

Site class vs. growth

• Stand growth of thinned stands may exceed that of no-thin on high sites

• Growth of thinned trees will always exceed no-thin trees; difference may be greatest on high sites

No-thin

Thin

Paired Plot Density Management (PPDM)Objectives

1. Describe growth-density function shape

2. Identify optimal time of thinning for small diameter stands

3. Evaluate site effects on thinning response

4. Thinning effects on light, water, and nutrients

Thinning operations throughout

the Inland Northwest

• 4 site classes x 3 density

classes

• Divided among three forest

types

101 PPDM study

locations

Site Productivity Class

Density 1 2 3 4

I 1 13 13 8

II 10 15 16 4

III 2 8 9 2

Site productivity10-yr increment estimates

DF PP WL

Minimum 15 10 20

25th 19 14 22

mean 23 18 25

75th 26 23 27

Maximum 31 27 30

Matrix grid evenly classified site conditions

• Corners were hard to fill

• High density larch not available

• Represents range of forest stand conditions

0

2 5

5 0

7 5

1 0 0D F

15 19 23 27 31

0

2 5

5 0

7 5

1 0 0

P P

Cu

rti

s'

Re

lati

ve

De

ns

ity

10 14 18 2723

0

2 5

5 0

7 5

1 0 0W L

T e n -ye a r H e ig h t G ro w th

20 22 25 27 30

PPDM within site plotDesign

• 3-4 plots at each location

• No-thin

• Operational thin

• Alternative thin

4.3 m 14 foot

5.5 m 18 foot

No thin, Control

Light to moderate thin, 10-14 foot

Moderate to heavy thin, 16-18 foot

Establishment results

• Stand structure

• Density distribution

• Dependent site factors

Structure modified by thinning

• Removal of ingrowth

• Shift mean diameter right

2 4 6 810

12

14

16

0

2 0 0

4 0 0

6 0 0

8 0 0D o u g la s - f ir

Tre

es

pe

r A

cre

D F T h in

D F N o th in

2 4 6 810

12

14

16

0

2 0 0

4 0 0

6 0 0

8 0 0 P o n d e ro s a p in e

D ia m e te r c la s s ( in )

2 4 6 810

12

14

16

0

2 0 0

4 0 0

6 0 0

8 0 0W e s te r n L a rc h

DF examples

Site 2Den 2

Site 4Den 1

Site 1Den 2

Site 2Den 2

Site 3Den 3

Site 4Den 3

Composition modified by thinning

• Increased composition of target species to almost 90%

• Little additional effect between spacing levels

• PP was less affected than others N

on

e

Lig

ht

Mo

dera

te

0

2 0

4 0

6 0

8 0

1 0 0

D o u g la s - f ir

Sp

ec

ies

Co

mp

os

itio

n (

%)

No

ne

Lig

ht

Mo

dera

te

0

2 0

4 0

6 0

8 0

1 0 0

W e s te r n L a rc h

D F

G F

W L

L P

P P

O th e r

T h in n in g T re a tm e n t

Stand metrics among experimental factors

• Basal Area

• Reflects experimental design

• Increases with density class in no-thin plots

• Decreases with thinning

• BA is not affected by productivity class

I I I I II

0

5 0

1 0 0

1 5 0

2 0 0

D e n s ity C la s s

Ba

sa

l a

re

a

(ft

2 a

c-1

)

N one

L ig h t

M o d e ra te

Stand metrics among experimental factors

• Stand Densityi.e. Curtis’ RD

• Increases with density class

• Thinning decreases density

• RD is not affected by site productivity class

1 2 3 4

0

5 0

1 0 0

1 5 0

D e n s ity I N one

L ig h t

M o d e ra te

1 2 3 4

0

5 0

1 0 0

1 5 0

D e n s ity II

Cu

rti

s'

Re

lati

ve

De

ns

ity

1 2 3 4

0

5 0

1 0 0

1 5 0

D e n s ity III

S ite P ro d u c tiv ity C la s s

Stand metrics among experimental factors

• Stand Densityi.e. Portion of SDImax

• Increases with density class

• Thinning decreases density

1 2 3 4

0

5 0

1 0 0

1 5 0

D e n s ity I N one

L ig h t

M o d e ra te

1 2 3 4

0

5 0

1 0 0

1 5 0

D e n s ity II

Pe

rc

en

t o

f M

ax

imu

m

Sta

nd

De

ns

ity

In

de

x

1 2 3 4

0

5 0

1 0 0

1 5 0

D e n s ity III

S ite P ro d u c tiv ity C la s s

Comparison among density metrics

0 1 2 3 4 5

0

2

4

6

ln C u rt is ' R e la tiv e D e n s ity

ln P

erc

en

t o

f M

ax

imu

m

Sta

nd

De

ns

ity

In

de

x

D F

W L

P P

0 5 0 1 0 0 1 5 0

-1 0 0

-5 0

0

5 0

1 0 0

R e s id u a ls : L in e a r re g . o f % S D Im a x v s R D

D E N S IT Y 0

Re

sid

ua

ls

D F

W L

P P

Stand metrics among experimental factors

• Diameter

• Low in stand density class I

• Thinning increases mean diameter, thinning from below

1 2 3 4

0

2

4

6

8

1 0

1 2

D e n s ity I N one

L ig h t

M o d e ra te

1 2 3 4

0

2

4

6

8

1 0

1 2

D e n s ity II

Qu

ad

ra

tic

Me

an

Dia

me

ter (

in)

1 2 3 4

0

2

4

6

8

1 0

1 2

D e n s ity III

S ite P ro d u c tiv ity C la s s

Ten-year Site Productivity explained by Climate and Topography

• Moisture

• Temperature

2 .0 2 .5 3 .0 3 .5 4 .0

0

6

7

8

9

1 0

ln E

lev

ati

on

(ft

)

r2

= 0 .2 1

2 .0 2 .5 3 .0 3 .5 4 .0

0 .0

0 .5

1 .0

1 .5

2 .0

ln A

nn

ua

l D

ry

ne

ss

In

de

x

r2

= 0 .1 7

2 .0 2 .5 3 .0 3 .5 4 .0

0

2

3

4

5

6

ln F

ro

st-

Fre

e P

erio

d (

d)

r2

= 0 .2 3

2 .0 2 .5 3 .0 3 .5 4 .0

0

3

6

7

8

ln D

eg

re

e D

ay

s >

5o

C

r2

= 0 .0 7

ln T e n - y e a r H e ig h t G r o w t h

PPDM Establishment Summary

• Rotation-long study designed to validate SDImax estimates

• Addresses where and when to most effectively thin stands

• Includes full range of productivity and stand densities

• Data analyzed through regression analysis or with analysis of variance

• Plot network will serve many purposes