1. Manipulate broadleaf density Tend individual Sw
Intimate Mixtures
Manipulate broadleaf density
Tend individual Sw

2. 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?
Lees (1966) found that removing aspen in a radius equal to two times the crown radius of white spruce resulted in significant increases in the diameter and height of white spruce.
These results suggest a substantial opportunity to increase growth and yield of treated white spruce through selective removal of aspen only around potential crop trees.
P. Comeau - U of A

3. Individually tend each Sw
Plant 200 to 400 Sw / ha
Individually tend each Sw
brush a radius around each stem

4. Iron Creek - year 1 - glyphosate
Wonowon - year 1 - spot treatment
Iron Creek - Year 10
Wonowon - year 12

5. 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

6. Photo Courtesy - D. Sidders CFS
Sw Individual Tree Release
Control
Treated
Control
Photo Courtesy - D. Sidders CFS

7. Tending individual spruce - Estimated effect of number of spruce treated on yield
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
P. Comeau - U of A

8. 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

9. Timeframe may extend beyond standard FGAP
Intimate Mixtures
Manage broadleaf density
Tend individual Sw
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

10. Relationships Between White Spruce Growth or Mortality and Basal Area of Aspen (based on Wright et al. 1998)
Basal area (m2/ha)
Source: Comeau 2000

11. 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

12. 60% light availability at 10,000 spha when QMD is around 3cm
Relationship of Understory Light Levels to QMD and density
60% light availability
at 10,000 spha when
QMD is around 3cm
Comeau 2001

13. Relationship of Understory Light Levels to Basal Area
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
Light available at a height of 1 metre

14. All of these stands have BA of 7
All of these stands have BA of 7.7 m2/ha and 60% light in the understorey
Mean DBH = 2.5 cm
Density = 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

15. 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

16. Manipulate Broadleaf Density - Conclusion
Understory light levels:
can be predicted
can be manipulated to favour Sw growth
can be manipulated to reduce At sprouting

17. 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

18. Regimes - Next Steps ? 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
P. Comeau