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Intimate Mixtures

Explore the impact of manipulating broadleaf density on spruce growth, with significant improvements seen after removing broadleaf overstory. Questions on treating tree quantity, radius, and age. Detailed research findings and conclusions provided.

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Intimate Mixtures

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  1. Tend individual Sw Intimate Mixtures Manipulate broadleaf density

  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? P. Comeau - U of A

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

  4. Wonowon - year 1 - spot treatment Iron Creek - year 1 - glyphosate 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. 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. 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

  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. Light availability decreases with depth in the aspen canopy Light availability below the aspen canopy is correlated with measurable stand attributes Manipulate Broadleaf Density - Light Regimes Growth of Sw is expected to be approaching maximum when light transmittance exceeds 60%

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

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

  14. All of these stands have BA of 7.7 m2/haand 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

  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

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