Tend individual Sw
Intimate Mixtures
Manipulate broadleaf density
Tending Individual Sw
• Significant improvements in diameter and height
growth for conifers have been reported following
removal of broadleaf overstory
• Questions:
– How many trees to treat?
– How large a radius to treat?
– What age to treat?
P. Comeau - U of A
• Plant 200 to 400 Sw / ha
• Individually tend each Sw
– brush a radius around each stem
Iron Creek - year 1 - glyphosate
Wonowon - year 1 - spot treatment
Iron Creek - Year 10
Wonowon - year 12
1951 - 25 Sw/aspen stands aged 5 to 65 years were selected
All competition within 2 times the Sw crown radius was
removed on 1/2 of the 656 sample trees
After 48 years release improved Sw growth by
•29% in diameter
•38% in height
•48% in volume over the control
Overall responses varied with site & age classes
Sw Individual Tree Release
Control
Control
Treated
Photo Courtesy - D. Sidders CFS
• Proportion of area treated
is a function of number of
spruce treated and
treatment radius
• Aspen yield estimated
from proportion of area
untreated
– Assume aspen yield of
260 m3/ha of aspen at
age 90 for untreated areas
– Assume a spruce yield of
150 m3/ha for untreated
areas
Proportion of block treated
Tending individual spruce - Estimated effect
of number of spruce treated on yield
1
0.8
0.6
0.4
0.2
0
0
200
400
600
800
1000
1200
Number of spruce treated (tph)
2
2.5
3
P. Comeau - U of A
Tending Individual Sw - Conclusions
• Long term research results confirm the
feasibility of individual tree release
• Ballpark volume projections can be made
for different scenarios using existing G&Y
information
Tend individual Sw
Intimate Mixtures
Manage broadleaf density
Manipulate aspen density to control light levels for:
Sw to develop into a codominant position
Minimize sprouting of cut aspen
Timeframe may extend beyond
standard FGAP
Full site occupancy with Sw
Apply treatments as required to establish Sw
Site preparation, planting , early brushing
establishment density should consider the potential for
whipping damage
Relationships Between White Spruce
Growth or Mortality and Basal Area of
Aspen
(based on Wright et al. 1998)
Source: Comeau 2000
Basal
area
2
(m /ha)
Manipulate Broadleaf Density - Light Regimes
Light availability decreases with
depth in the aspen canopy
Growth of Sw is expected to be
approaching maximum when
light transmittance exceeds 60%
Light availability below the aspen canopy is correlated
with measurable stand attributes
Quadratic mean diameter
(cm)
Relationship of Understory Light Levels to QMD and density
20
15
60% light availability
at 10,000 spha when
QMD is around 3cm
10
5
0
0
2000
4000
6000
8000
10000
Aspen density (sph)
difn=0.6
difn=0.4
difn=0.2
Comeau 2001
% of full sunlight
Relationship of Understory Light
Levels to Basal Area
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
To maintain 60 % full light the basal
area needs to be reduced to less than 8
To maintain 40% full light requires
a basal area of 14m2
0
10
20
30
Broadleaf basal area (m 2/ha)
Light available at a height of 1 metre
40
50
All of these stands have BA of 7.7 m2/ha
and 60% light in the understorey
Mean DBH = 2.5 cm
Density = 15 675
stems/ha
Mean DBH = 4.0 cm
Density = 6125 stems/ha
Mean DBH = 7.0 cm
Density = 2000 stems/ha
Density is not a good predictor of light regimes
Aspen distribution is regular
within small areas, but varies across a
single site.
Prescriptions to manipulate broadleaf densities need to take
this variation into account
Manipulate Broadleaf Density Conclusion
• Understory light levels:
– can be predicted
– can be manipulated to favour Sw growth
– can be manipulated to reduce At sprouting
Manipulate Broadleaf Density
Conclusion cont’d
• Tables or graphs of light transmittance can
be used to make decisions on appropriate
levels of aspen density
• Combined with an aspen growth model the
table could be used to predict light
transmittance over time & timing
requirements of future At spacing
Regimes - Next Steps ?
600
500
0
107
400
300
208
156
260
491
200
288
100
104
158
357
218
150
286
355
Herbicide
60%
herbicided
(patches)
40%
herbicided
(patches)
20%
herbicided
(patches)
300 Sw/ha
x 2.5 m
200 Sw/ha
x 2.5 m
0
Untreated
Yield (total) (m3/ha)
• Detailed development & analysis of
regimes
– Calculation of Establishment
Costs
• $/ha and $/m3
– Estimates of Likelihood of
Success
– Regime Details (specifics)
– Growth & Yield Implications
– Financial Analysis
• Determination of Viable Regimes
– Establish Stocking Standards
– A “Due Diligence” Process to
Support Management Decisions
Sw Vol Aw Vol
P. Comeau