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

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

Individually tend each Sw 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

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

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

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

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

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

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

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

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

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 = 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 ? 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