Stand dynamics after variable retention
harvesting in mature Douglas-fir forests
of western North America
Doug Maguire, Doug Mainwaring
Department of Forest Science
Oregon State University
100%
40%D
13 ha
75%A
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Regeneration/Stand Structure
• What was the initial stand structure?
• What was the immediate post-harvest stand
structure?
• How has stand structure responded 5 years after
harvest?
– Overstory growth and mortality
– Planted seedling growth and mortality
– Advance regeneration release
• What are the treatment units likely to look like
under alternative treatment scenarios?
40%A
15%D
Can retaining some structural
variability attain biodiversity objectives
that a patchwork of clearcuts cannot?
Key Needs of DEMO
• To provide variety of stand structures over
space and time, need knowledge of stand
dynamics after innovative silvicultural
treatments
• Field study has to have statistical rigor, but
• Also has to be applied at a scale that:
– Accommodates species/responses of interest
– Allows realistic assessment of operational
feasibility
– Yields information relevant to management
decisions and policy formulation
Regeneration/Stand Structure
• What was the initial stand structure?
• What was the immediate post-harvest stand
structure?
• How has stand structure responded 5 years after
harvest?
– Overstory growth and mortality
– Planted seedling growth and mortality
– Advance regeneration release
• What are the treatment units likely to look like
under alternative treatment scenarios?
40-m sampling grid in
13-ha treatment unit
7X9
OR
8X8
Sampling vegetation
11.28 m radius
TREATMENT EFFECTS
Overstory trees (0.04 ha)
Snags
(0.08 ha)
Canopy cover
Shrubs, CWD,
& disturbance
1m
Herbs, cryptogams, & tree seedlings
Understory trees
6m
Watson Falls - Treatment 3
50
40
Psme
Abco
35
Tshe
Cach
Tsme
Abmas
Pipo
Abam
Pimo
Pico
30
25
20
15
10
5
Dbh class (cm)
14
5
13
5
12
5
11
5
10
5
95
85
75
65
55
45
35
25
15
0
5
Trees per hectare
45
White fir
Red fir
Western hemlock
Western redcedar
Grand fir
western hemlock
Western hemlock
Western redcedar
Pacific silver fir
Red alder
Western hemlock
Western redcedar
Significant differences among blocks and
treatment units in initial basal area
120
Basal area (m 2 /ha)
Treatments
100
100
75
40D
40A
15D
15A
80
60
40
20
0
Watson Falls
Dog Prairie
Butte
Little White
Salmon
Block
Paradise
Capitol
Crown area profile
horizontal
slice through
canopy
Crown area profile
crown crosssectional area
at height h
Crown area profile
slices through
canopy at fixed
height intervals
Crown area profile
sum crosssectional
areas at each
height
Crown area profile
height
Crown area
Crown area profiles before harvest
70
70
(a)
50
Psme
Abam
Abpr
Thpl
Tshe
(b)
WF
DP
BU
LW
PH
CF
60
40
blocks
(c)
60
50
species
30
plots
40
40
Height (m)
=
20
30
30
20
20
10
10
10
0
0
0
0
10000
20000
0
4000
8000
2
12000
Crown area (m /ha)
0
10000
20000
DEMO field data sampling timeline
Harvest
2nd post-harvest
tree sampling
4- or 5-yr response
?
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Pre-harvest
sampling
1st post-harvest
sampling
DEMO
units
logged in
1997 &
1998
Regeneration/Stand Structure
• What was the initial stand structure?
• What was the immediate post-harvest stand
structure?
• How has stand structure responded 5 years after
harvest?
– Overstory growth and mortality
– Planted seedling growth and mortality
– Advance regeneration release
• What are the treatment units likely to look like
under alternative treatment scenarios?
Six treatments
defined by level and pattern of basal area retention
100%
75%A
40%A
40%D
15%A
15%D
Stand ages:
65-170 years.
Homogeneous
upland forests riparian areas
and roads were
avoided.
Harvest methods
and post-harvest
silvicultural
prescriptions
varied among
blocks, but not
within blocks.
Unharvested
control
Watson Falls - Treatment 3, remove largest DF
Watson Falls - Treatment 3, remove smallest DF
50
45
Pico
40
Abam
35
Pimo
30
Pipo
45
Trees per hectare
Abmas
25
Cach
20
Tsme
15
Tshe
10
Abco
5
Psme
Abam
35
Pimo
30
Pipo
25
Abmas
20
Cach
15
Tsme
Tshe
10
Abco
5
Psme
Dbh class (cm)
14
5
13
5
12
5
11
5
10
5
95
85
75
65
55
45
35
25
5
14
5
13
5
12
5
11
5
Watson Falls - Treatment 3 , actual treatment
10
5
95
85
75
65
55
45
35
25
0
15
0
5
Pico
40
15
Trees per hectare
50
Dbh class (cm)
50
Pico
40
Abam
35
Pimo
30
Pipo
25
Abmas
20
Cach
Tsme
15
Tshe
Psme
Abam
35
Pimo
30
Pipo
25
Abmas
20
Cach
15
Tsme
Tshe
10
Abco
5
14
5
13
5
11
5
10
5
95
85
75
45
Pico
Dbh class (cm)
40
Trees per hectare
Pico
40
65
55
45
5
35
45
Watson
Falls - Treatment 3 , from below
Abco
50
25
0
15
50
Abam
35
Pimo
30
Pipo
25
Abmas
20
Cach
Tsme
15
Tshe
10
Abco
5
Psme
0
Psme
Dbh class (cm)
Dbh class (cm)
14
5
13
5
12
5
11
5
10
5
95
85
75
65
55
45
35
25
15
5
14
5
13
5
12
5
11
5
10
5
95
85
75
65
55
45
35
25
0
15
5
Trees per hectare
Watson Falls - Treatment103, remove DF & WF
5
proportionally
12
5
Trees per hectare
45
Residual basal area within a common retention
level varied significantly
120
Watson Falls
Dog Prairie
Butte
Basal area (m 2 /ha)
100
80
Little White Salmon
Paradise Hills
60
Capitol Forest
40
20
0
100%
75%A
40%D
40%A
Treatment
15%D
15%A
Residual basal area as a % of control
120
% of control basal area
Treatments:
100
75
40D
40A
15D
15A
100
80
60
40
20
0
Watson Falls Dog Prairie
Butte
Little White
Salmon
Block
Paradise
Hills
Capitol
Forest
Dispersed canopy cover > aggregated canopy cover
Canopy cover (%)
100
100%
75%A
40%D
40%A
15%D
15%A
80
60
40
20
0
Watson
Falls
Dog Prairie
Butte
Little White Paradise
Salmon
Hills
Block
Capitol
Forest
100%
75%A
200
residual
cut
150
150
100
100
50
50
0
0
40%A
40%D
200
Trees per ha
Residual trees
in dispersed
treatments
selected from
dominants and
codominants
75%A
100%
200
40%A
40%D
200
150
150
100
100
50
50
0
0
15%A
15%D
200
15%A
15%D
200
150
150
100
100
50
50
0
0
0
10
20
30
40
50
60
70
80
90 0
10
20
30
Dbh class midpoint (cm)
40
50
60
70
80
90
Principal components of diameter distribution
(a) Before treatment
Capitol
Forest
Dog
Prairie
Axis 2
Paradise
Hills
Watson
Falls
Butte
Little
White
Salmon
Axis 1
Principal components, after treatment
(b) After treatment
100% (control)
Paradise
Hills
Axis 2
Butte
Dog
Prairie
Capitol
Forest
Watson
Falls
Little
White
Salmon
15%A
Axis 1
Crown area profiles after harvest, by treatment
70
70
Paradise Hills
Watson Falls
Height (m)
50
50
40
40
30
30
20
20
10
10
0
0
0
2000
4000
100%
75%A
40%D
40%A
15%D
15%A
60
100%
75%A
40%D
40%A
15%D
15%A
60
6000
8000
0
2
3000
Crown area (m /ha)
6000
9000
12000 15000
Residual tree density
40%D:
87, 112, 139, 147, 152, 512 tph
(35, 45, 56, 60, 62, 207 tpa)
40%A:
25, 27, 29, 48, 77, 229 tph
(10, 11, 12, 19, 31, 93 tpa)
15%D:
39, 54, 57, 86, 92, 176 tph
(16, 22, 23, 35, 37, 71 tpa)
15%A:
35, 38, 39, 55, 81, 147 tph
(14, 15, 16, 22, 33, 60 tpa)
DEMO field data sampling timeline
Harvest
2nd post-harvest
tree sampling
4- or 5-yr response
?
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Pre-harvest
sampling
1st post-harvest
sampling
Regeneration/Stand Structure
• What was the initial stand structure?
• What was the immediate post-harvest stand
structure?
• How has stand structure responded 5 years after
harvest?
– Overstory growth and mortality
– Planted seedling growth and mortality
– Advance regeneration release
• What are the treatment units likely to look like
under alternative treatment scenarios?
Residual basal area by block and treatment
Overstory stem volume growth
Stand growth =
f(stand density)
Growth per unit
initial basal area
tends to decline
with lower
retention
Growth per unit
initial basal area
of 25 largest per
ha not affected by
treatment
Overstory stem volume growth
Stand growth:
Control > 40% > 15%
Growth per unit initial volume is
greater under dispersed retention
Growth per unit initial volume of only
the 25 largest trees per ha was not
affected by trt
BUT, evidence probably
accumulating that this relative
growth rate will be great in dispersed
treatment and at lower retention rate
Overstory periodic annual mortality
Greater
mortality in
15%D
Douglas-fir
Wind damage in 15%D treatments
Stem breakage
Uprooting
Overstory periodic
annual mortality
Interaction between
level and pattern for
Douglas-fir
Greater for
dispersed treatments
and at lower
retention level for
other conifers
Regeneration/Stand Structure
• What was the initial stand structure?
• What was the immediate post-harvest stand
structure?
• How has stand structure responded 5 years after
harvest?
– Overstory growth and mortality
– Planted seedling growth and mortality
– Advance regeneration release
• What are the treatment units likely to look like
under alternative treatment scenarios?
Height growth of planted seedlings
Height growth
increases with
decreasing
overstory
competition
Some trend for
greater growth in
cut areas of
aggregated
treatments,
particularly at
40%
Pinus ponderosa
Pinus monticola
Douglas-fir
Abies procera/amabilis
Height growth of planted seedlings
level
pattern
level
pattern
interaction
level
pattern
Cumulative mortality of planted seedlings
Ponderosa
pine (Pipo):
heavy
mortality
under shade
Douglas-fir
(Psme):
heavier
mortality
under more
open canopy
between
aggregates
Western white
pine (Pimo):
Heavier
mortality in
cut areas of
aggregated
retention
Cumulative mortality of planted seedlings
pattern
interaction
level
pattern
No trt
effects
Dead tops on planted seedlings
DF: high on
40%D, low on
15%A
Abies: high
on 15%D, low
on 40%A
WWP: high on
15%D
Does a greater rate of past top damage
imply greater susceptibility after treatment?
Post-treatment
Broken tops
Types of top
damage:
Pre-treatment
Multiple tops
Crook in crown
Top damage before and after treatment
10% of all trees had some form of top damage
Incidence was greatest in suppressed (19%) and
intermediate (15%) crown classes, 79% of all
multiple tops and 89 % of all crooks
Less than 1% of dominant trees were damaged,
and only about 4% of codominants
2.6% of conifers had multiple tops and 4.1% had a
crook within the crown
Almost half of the trees with crooks were western
hemlock, although only 19% of total stems were
hemlock
Top damage before and after treatment
3.1 % of all Douglas-fir trees had broken tops, as
did 4.4% of western hemlock
58% of trees with broken tops were suppressed,
and 30% were intermediate; no dominants had
broken tops and only 1.1% of codominants
No treatment effects for Douglas-fir or western
hemlock, nor for all codominant and intermediate
trees
Suppressed trees had a higher rate of broken tops
in dispersed treatments than in aggregated
treatments, but level of retention had no effect
Proportion with condition
Top damage, all conifers
0.0700
bt
0.0600
Broken top
mt Multiple top
0.0500
cc Crook in crown
0.0400
0.0300
0.0200
0.0100
0.0000
100%
1
75%A
2
40%D
3
40%A
4
Treatment
15%D
5
15%A
6
Top damage in Douglas-fir
Proportion with condition
bt
Broken top
0.0350
mt Multiple top
0.0300
cc Crook in crown
0.0250
0.0200
0.0150
0.0100
0.0050
0.0000
100%
1
75%A
2
40%D
3
40%A
4
Treatment
15%D
5
15%A
6
Regeneration/Stand Structure
• What was the initial stand structure?
• What was the immediate post-harvest stand
structure?
• How has stand structure responded 5 years after
harvest?
– Overstory growth and mortality
– Planted seedling growth and mortality
– Advance regeneration release
• What are the treatment units likely to look like
under alternative treatment scenarios?
Blocks investigated
for advance
regeneration
response
2002 height growth of advance
regeneration: Pacific silver fir (Abam) and
white fir (Abco)
Silver fir may
release more
(one block each!)
readily under full
exposure
White fir may take
a longer period to
acclimate
BUT, on species
level only one
block is
represented;
hence, treatment
is totally
confounded with
all other site
factors of the
respective
treatment units
Growth release of Abies amabilis
advance regeneration
open
2002
shaded
2002
2001
2001
2001-2002 height growth of advance regeneration:
Douglas-fir (Psme) and Abies (A. amabilis + A. concolor)
Height growth for
last TWO years
shows weak
trends, but Abies
release increases
with decreasing
retention
2002 height growth of advance regeneration:
Douglas-fir (Psme) and Abies (A. amabilis + A. concolor)
(Two blocks only)
Increasing
release in
Abies with
lower
retention
Less
pronounced
release in
Douglas-fir
But, by 2002
seedlings are
better
acclimated
and
expressing
treatment
effects more
strongly
2002 height growth of advance regeneration
level
Abies
Douglas-fir
No trt
effects
Release index
∆hpost/∆hpre = ∆h1998/∆h1997
(for Paradise Hills)
2002
2001
2000
1999
1998
1997 (harvest trt)
Release index of advance regeneration
(post-harvest dH / pre-harvest dH)
Shock appears to
have had less
effect on
Douglas-fir than
Abies in 15%A,
despite the fact
that by 2002
Abies has
responded more
strongly to
release
Regeneration/Stand Structure
• What was the initial stand structure?
• What was the immediate post-harvest stand
structure?
• How has stand structure responded 5 years after
harvest?
– Overstory growth and mortality
– Planted seedling growth and mortality
– Advance regeneration release
• What are the treatment units likely to look like
under alternative treatment scenarios?
How to communicate the concept of stand
dynamics and stand structural options to
multi-disciplinary teams
and
identify mutually acceptable silvicultural
treatments?
SIMULATION
and
STAND VISUALIZATION
Simulation: Evaluate scenarios for possible
alternative follow-up treatments
Simulation objectives:
• Projection of stand structure; test of treatments
• Visualization of future structure & conditions
• Design of treatment schedule by interdisciplinary
team of scientists
• Initial guidelines for variable retention silvicultural
systems that meet multiple objectives
• Public education and acceptance
Management regimes:
(1) No silvicultural intervention
(2) Remove 50% of understory
cohort at yr 50
(4) Maintain 35-55% of maximum
SDI by proportional thinning of
understory cohort
1.00
0.55
0.35
Tree size
(3) Maintain 35-55% of maximum
SDI by proportional thinning of
both understory and overstory
cohorts
Density
Paradise Hills, 15%D
Proportional thinning of
understory at 55% max SDI
T5,M5, 100
Year 100
T5,M5, 15
Year 15
T5,M5, 100
Paradise Hills, 15%D
Proportional thinning of
understory and overstory at
55% max SDI
T5,M3, 50
T5,M3, 15
T5, M3, 100
Paradise Hills, 15%D
T5, control, 100
T5, M3, 100
T5, M1, 100
T5, M5, 100
Paradise Hills, 40%A
Year 100
Proportional thinning of understory
cohort at 55% max SDI
T4, M3, 100
Proportional thinning of understory
and overstory at 55% max SDI
T4, M3, 100
Capitol Forest 15%D
Remove 50% of trees in yr 50
Yr 15
T5, M1, 15
Yr 50
T5, M1, 50
T5, M1, 50
Year 100
Capitol Forest 40%A
No thinning
Year 15
T4, 50
T4, 15
Proportional thinning of understory and
overstory cohorts at 55% max SDI
T4, M3, 50
Dog Prairie, 40%A
20 yrs
c
60 yrs
100 yrs
Capitol Forest (CF): 15%D treatment, 100-yr simulation
No further treatment
Initial stand at
15 yrs
Maintain stand at 35-55% maximum
density
120
100
80
60
C
UT
UOT
40
20
100%
120
100
80
60
Total crown cover (%)
Trends in canopy
cover by variableretention
regeneration harvest
and subsequent
stand density
management regime
40
20
120
40%D
100
80
60
40
20
120
40%A
100
80
60
40
20
120
15%D
100
80
60
40
15%A
20
1980
2000
2020
2040
2060
Simulation year
2080
2100
2120
HARVEST, POST-HARVEST ACTIVITIES, FUTURE
TREATMENTS,
TREATMENTS and
DESIGN OF A SILVICULTURAL SYSTEM
Yarding
• Ground based
• Helicopter
Snag creation
Slash treatment
• None
• Pile and burn
Overstory
cohort
• Topping
• Girdling
Future
treatments ?
Planting
• 300-500 trees / ha
• Mix of species
Understory cohort
Future
treatments ?
Adaptive management !
Silvicultural systems
efficacy for
biodiversity
target species
ecological functions
number of taxa/alleles
social
acceptance
aesthetics
environmental impact
recreational opportunities
silvicultural
feasibility
BIOLOGICAL
operational
economic
Thanks!
!
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