Disturbance-Based Management• Landscape-Level
– Pattern and complexity – Stand age class distributions – Patch distributions: type, size, – shape, and continuity– Habitat representation– Historic range of variability
• Stand-Level– Vertical structure
– Horizontal structure
– Cohorts
– Tree age class distributions
– Biological legacies
Figure adapted from Franklin and Spies (1991).
Structural Change Through Stand Development
Photos courtesy of Jerry F. Franklin, University of Washington
Recovery facilitated by biological legacies at
Mount St. Helens
Large-scale Windthrow: Hurricanes
Fine-scale Windthrow
Ice Storms
Insect and Pathogens Outbreaks
Coarse Woody Debris in Northern Hardwood Forests
Even-aged Single-tree Selection Old-Growth
• Habitat
• Nitrogen Fixation
• Soil organic matter
• Mycorrhizal fungi
• Nurse logs
• Erosion reduction
• Riparian functions Figure from McGee et al. (1999)
Teakettle Ecosystem Experiment
Forest Ecosystem Research Network
0 %
100 % 80 %
20 % 80 %
20 %Removal at Harvest
Retention at Harvest
Entries per Rotation
Age Classes
12 - 3
4 or more
Even-aged (1 class) Multi-aged (2-3 classes)
Uneven-aged (4 or more classes)
Figure from Franklin et al. (1997)
Variable Retention Harvest System
“Demonstration of Ecosystem Management Options”
Weyerhaeuser Co. Variable Retention Adaptive Management (VRAM) Experiment
Weyerhaeuser Co. Variable Retention Forestry in B.C.
VRAM
Year 0
Year 15
Long-Term Implications ?
What have we learned about natural disturbance effects?
• Scale and frequency of disturbance
Figures from Seymour et al. 2002
Mimicking scale and frequency of disturbances
0
0.5
1
1400 1500 1600 1700 1800 1900
Year
Prop
ortio
n of
Lan
dsca
pe in
Old
-gro
wth
HRV
Historical Range of Variability
Figure from Aplet and Keeton (1999)
0
0.5
1
0 100 200 300 400 500
Years
Pro
po
rtio
n o
f L
and
scap
e in
Old
-gro
wth
0
0.5
1
0 100 200 300 400 500
Years
Pro
po
rtio
n o
f L
and
scap
e in
Old
-Gro
wth
0
0.5
1
0 100 200 300 400 500
Years
Pro
po
rtio
n o
f L
and
scap
e in
Old
-Gro
wth
HRV
HRV
HRV
Scale: Small Watershed
Scale: Drainage Basin
Scale: Region
Hurricane
Hurricanes
Source: Aplet and Keeton (1999)
HRV
Historical Range of Variability
Figure modified from Aplet and Keeton (1999) using data from Cogbill (2000)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1300 1350 1400 1450 1500 1550 1600 1650 1700
Year
Pro
po
rtio
n o
f L
and
scap
e in
Ear
ly-S
ucc
essi
on
What have we learned about natural disturbance effects?
• Coarse-woody debris: snags and downed wood
Coarse Woody Debris in Northern Hardwood Forests
Even-aged Single-tree Selection Old-Growth
• Habitat
• Nitrogen Fixation
• Soil organic matter
• Mycorrhizal fungi
• Nurse logs
• Erosion reduction
• Riparian functions Figure from McGee et al. (1999)
What have we learned about natural stand development?
• Importance of large trees as structural elements
Crown Release to Increase the Representation of Large Trees
30
60
150 300
Age (Years)
DB
H (
cm)
No release
Partial crown releaseFull crown release
Data from Singer and Lorimer (1997)
What have we learned about natural stand development?
• Vertical complexity
• Horizontal complexity
Structural Complexity Index (Zenner 2000)
A)
B)
= Ratio of 3D area in A to 2D area in B
Uneven-aged Forestry
• Single-tree selection
• Group selection
BDq prescriptions are based on the desired:
1. residual basal area
2. maximum dbh
3. q-factor
00 24
7
14
83610
7
94
0
20
40
60
80
100
120
2.0-4.0 4.0-6.0 6.0-8.0 8.0-10.0
10.0-12.0
12.0-14.0
14.0-16.0
16.0-18.0
18.0-20.0
20.0-22.0
22.0-24.0
>24.0
Current
Target
Cull
Single-Tree Selection Prescription for Mt. Mansfield Unit 4: q-factor of 1.3, maximum diameter of 24", and residual basal area of 80 ft2/acre
Diameter Class in Inches
# S
tem
s p
er A
cre
Diameter Distributions
Figure from Goodburn and Lorimer (1999)
Unbalanced Diameter Distributions:
Figure from Goodburn and Lorimer (1999)
• Density-dependent mortality reduced with fewer stems in smaller size classes
• Equal allocation of growing space not found consistently
Figure from Seymour 2005
Multi-modal distributions due to old-tree legacy
Rotated Sigmoid Diameter Distribution
Shift in basal area allocation to larger size classes
• Often found in old-growth northern hardwoods and mixed-woods
• Varies with disturbance history, stand composition, and competitive dynamics
• Theoretical silvicultural utility proposed (O’Hara 1999, Leak 2003); tested experimentally by Keeton (2005).
# of
Tre
es
Diameter Class
Yield vs. Big Tree Structure in Northern Hardwoods
40 cm max. 50 cm max. 80-100 cm max.
Data from Hansen and Nyland (1987) Data from Goodburn and Lorimer (1999)
Maximized volume production
Selection harvest + old-growth structure
after multiple cutting cycles
Maximized large sawtimber volume and value growth
An Alternative: Multi-aged Silviculture
• Recognizes that “reverse J” is limiting
• Other stand structures are sustainable
• Ecological functions more closely associated with canopy structure
• All-aged stands exceedingly rare in actuality
• Management based on the desired number of canopies provides a better alternative
• Set objectives based on canopy strata two-aged and multi-aged are possibilities
Multi-aged distributions resulting from multiple disturbances
Diameter Class
Trees/ha
– Leaf area index
– Stand density index
– MASAM model (O’Hara 1998)
Growing space allocation approachesPercent of trees per acrePe
rcen
t of
basa
l are
a
Bottom Layer Mid Layer Top Layer
Percent of growing space
553510
25
33
42
57
33
10
Shift in growing space from one strata to another also shifts growth increment
Hig
hL
ow
Understory growth
Overstory growing space occupied (%)
0 50 100
Overstory growth
High
Low
Understory
Overstory
Figure from O’Hara (1998)
Conversion to Multi-Aged or Multi-Canopied
Managing for Canopy Strata
• Fewer and longer cutting cycles
• Management across multiple spatial scales– Need combination of single and multi-layered
stands to maximize biodiversity potential
Ind
epen
dan
t
Geomorphology
Geology
GPM type
Mode ofdeposition
Intial static conditionsHydrology
Waterways
Watershed
Topography
slope,orientation,
altitude
Meteorology
Temperature,precipitation
Climate
Climaticzone
Non-forested
Agriculturalland,roads
Natural disturbances
Dynamic processesFire
Size,Intensity,
Frequency
Epidemics
Size,Intensity,
Frequency
Windthrow
Size
Landscape
Watershed
Stand
Scale
Scale
Stand
Watershed
Landscape
Imp
ose
d
Statusquo
Harvesting scenarios
Management scenarios
Multiplepass
Partialcutting
Triad
Scale
Stand
Watershed
Landscape
Constraints expressed in terms of indicators
Sustainable forest managementSoils Regeneration Biodiversity Aquatic
Rotation period,geology,
stand type,harvesting
method
Age structure,composition,
configuration, roads,bird monitoring
mineral soil,stocking and growth
of seedlings,compétition
Distance to seedtrees, age and
species ofseed trees
% watershedharvested,
dissolved P and C,transparency
Governmentstandards
Forested land
Initial dynamic conditionsProductive
Initial ForestConditions
Poor soils,slow growing
species
Unproductive
Barren,semi-barren,
Marginal
Modelling elements
Indicators of biodiversity
• Crit1: Maintenance of ecosystem diversity– Ind1.1: Age structure of the forest (P)– Ind1.2: Forest species composition (P)– Ind1.3: Configuration of the forest (P)
• Crit2: Maintenance of species diversity– Ind2.1: Road density (P)– Ind2.1: Monitoring bird populations (M)
100 year forest rotation
100 year fire cycle
Proposed age class distribution for managed forest
Ind1.1: Age class structure
Extended Rotations
Mean annual increment
Periodic annual increment
Stand age10 100
Cub
ic f
t./ac
re/y
ear
0
300
Advantages of extended rotations:
• Reduced land area in regeneration and early-development stages, hence:
1. Reduced visual impacts
2. Lower regeneration and respacing costs
3. Less need for herbicides, slash burning, etc.
4. Reducing frequency of intense disturbance
• Large tree and higher-quality wood
• Adjust precently unbalanced age distributions
• Higher quality habitat for species associated with late-successional forest structure
• Hydrologic benefits
• Increased carbon stock associated with increased net biomass/larger growing stock
• Preservation of options for future adaptive management
Landscape Management System (LMS)
Simulated landscape based on individual stand structures + important features (e.g. roads, streams, etc.)