Download Lecture 10 - FRST 305 | Silviculture

Mixed Species Silviculture
Objectives
1. Understand stratification of mixed
species stands
2. Understand role of height growth
patterns
3. Understand role of shade tolerance
4. Understand some different ways of
managing mixed species stands
Number of trees
Diameter Distribution
DBH
Different Inherent Height
Growth Patterns
1.
2.
3.
4.
Sigmoidal
Linear
Asymptotal (tall)
Asymptotal (short)
Height
Height Growth Patterns
Age
Shade Tolerance
• A species cannot survive under itself
• A species cannot survive under a more
shade tolerant species
Shade Tolerance
Shade intolerant
Ps
Shade tolerant
Light
Stratification
• Height growth patterns
• Role of spacing
Spruce and aspen
How to Manage
• Single cohort (even-age)
• Layercake
• Thin in all layers
• Multi-cohort?
Layer Cake
• Take off layers by height stratum
• Layers become more shade tolerant
• Plays out (even-age management)
Differentiation Within Stratum
• Vigor classes within stratum
• Differentiation less strong in lower strata
• Layer cake approach is often combined
with thinning in lower strata
Yield
• Volume of mixed species will not exceed a
pure stand of the most shade tolerant
species
• Monetary yield will almost always exceed
either species
Yield
TOTAL
100%
50%
0%
100% A
0% B
50% A
50% B
0% A
100% B
Yield
TOTAL
100%
50%
0%
100% A
0% B
50% A
50% B
0% A
100% B
Yield
6 m3
3 m3
0 m3
100% A
0% B
50% A
50% B
0% A
100% B
Mixed Portfolio
• Keep options open
• Values keep changing