1. Competitive Interaction of Aspen – Lodgepole pine mixedwoods in the Sub boreal forest: Implication for reforestation policy and practices in British Columbia (BC)
Christopher D.B. Hawkins and Amalesh Dhar
Mixedwood Ecology and Management Program
University of Northern British Columbia, BC
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2. Outline 1. Information about BC forest management 2. Objectives
3. Materials and Methods
4. Results
5. Conclusion
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3. Introduction Vegetation management in BC:
historically BC reforestation policies and regulations are conifer-biased
broadleaves species (birch, aspen) are routinely removed from plantations
- maximize crop tree growth
maintaining BC’s free-to-grow standard (BC Ministry of Forests 2000 )
“a stand of healthy trees of a commercially valuable species, the growth of which is not impeded by competition from plants, shrubs or other trees”
stands may only be declared free to grow when 2/3 years have passed since chemical or manual brushing treatment applied
all broadleaves vegetation treated as a competitor
BC = forestry dependent province
44.5 million hectares of commercial forest land;
Harvest = 70 million cubic meters
20% of Canadian total
Plant more than 200 million seedlings annually
Values of shipments = 24 billion CDN$; ~$14.6 billion Euro
Accounts for 1/3 of Canada’s total forestry shipments
Employs 270 k: Direct = 90k and 180 indirect
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Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar

4. Vegetation management in BC:
Introduction
Vegetation management in BC:
avoid administrative delays to get responsibility of the stand management
broadleaf species must be less than 1000 sph
practice has been consistently applied across much of Canada
Few years earlier Province of Alberta has changed this rule and made free growing standard should be location specific. Depending on the site condition broadleaf density may vary.
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5. Objectives Objectives
to examine the growth response of pine to varying levels of imposed aspen densities
test the effectiveness of current BC free-growing criteria
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6. Materials and Methods 9/14/2018 6
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7. Materials and Methods Location :
Vama Vama Creek , Prince George, BC, Canada
Zone: SBSwk1, wet and cool
Latitude: 53°52’12” N
Longitude: 122°09’46” W
Elevation: 775 m asl
Mean annual precipitation: mm (25-50% falls as snow)
Mean annual temperature: °C
Stand Age at plot establishment: 12 year-old stand
Stand: predominantly lodgepole pine and aspen (lesser amounts of spruce and subalpine fir)
USA
Canada
USA
Canada
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8. Experimental design and data collection (Experiment 1)
Materials and Methods
Experimental design and data collection (Experiment 1)
Design: completely randomized design
Treatment: Six different aspen densities replicated three times
- 0, 500, 1200, 2500, 5000 sph, and control
Plot establishment year (age of 12 years)
- total 18, 50 m X 50 m treatment units
- permanent plot (PSP) size m radius (100 m2)
- broadleaf species other than aspen were cut within 1.5 m of pine
- Plots were sampled at establishment and three times between ages 14 to 18 years
To meet the treatment density the broadleaf species other than aspen were cut within 1.5 m of lodgepole pine for facilitating the pine aspen competition 8
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9. Materials and Methods
Experimental design and data collection (Experiment 2)
equal numbers of free growing (FTG) and not free growing (NFTG) pine selected and tagged
-Pine with no aspen within the effective growing space (1 m radius cylinder centered on the pine) were classed as free growing
Crown dimensions, height and DBH measured in 2000, 2001,2003 & 2006
Leaf area index (LAI) measured for both FTG and NFTG pine
- midsummer of 2001 and re-measured in summer 2005
Light transmission measured by LiCor LAI-2000 (LiCor Inc., Lincoln NB) for FTG & NFTG
- diffuse non-interceptance (DIFN) values are estimated of average growing season fractional transmittance (i.e., percent of open-sky light)
- measurements at 1.3 m above the ground in midsummer 2005
- two readings from opposite directions were taken with 180° view restrictors
The LiCor system requires open-sky, as well as understory, measurements in order to calculate DIFN.
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10. Results
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11. Results: Experiment -1
Mean pine and aspen diameter (± SEM) at plot establishment and pine MA diameter growth
5000 sph (stem ha-1) of aspen appears to be the critical density
- diameter growth of the pine was significantly (p = 0.005) affected
2500 sph was the threshold density
- diameter growth of the pine was not significantly (P = ) affected
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12. Results: Experiment -1
Mean pine and aspen height (± SEM) at plot establishment and pine MA height growth
pine height growth showed insignificant relationship
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13. Results: FTG and NFTG (Exp. 2)
Repeated measures ANOVA from 2000, 2001, 2003 and 2006 in comparing height, diameter and crown volume for FTG and NFTG pine
Source SS DF MS F P
Height 1
0.237
0.628
Error 80
DBH
108.91
0.069
0.794
Crown Vol.
51.51
0.083
0.774
617.82
FTG and NFTG pine were not significant differ for DBH, height and crown volume
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14. Results: FTG and NFTG (Exp. 2)
FTG and NFTG showed similar DBH growth response in 2002 to 2006
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15. Results: FTG and NFTG (Exp. 2)
FTG and NFTG showed similar DBH growth response in 2002 to 2006
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16. Results: FTG and NFTG (Exp. 2)
FTG and NFTG showed similar DBH growth response in 2002 to 2006
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17. Results: FTG and NFTG (Exp. 2)
height of FTG pine was similar with NFTG pine
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18. Results: FTG and NFTG (Exp. 2)
FTG or NFTG pine was not significantly differ for different densities
LAI of pine increased with increased of aspen density
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19. Results: FTG and NFTG (Exp. 2)
FTG and NFTG pine were not significantly differ for different density classes
DIFN for pine decreased with increased of aspen density
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20. Results: FTG and NFTG (Exp. -1)
pine DBH growth slightly increased with the increase of DIFN
- response was not significant
least DBH growth was observed at lower DIFN in NFTG pine
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21. Conclusion
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22. Conclusion Impact on overall pine growth
pine DBH growth not impacted by up to 2500 sph aspen
pine DBH growth significantly impacted with 5000 sph aspen
Pine height growth not significantly differed by density treatment
Impact on FTG and NFTG pine
no significant differences between FTG & NFTG pine in height, DBH and crown volume
rate of change of DFIN and LAI is similar up to 2500 sph but rate of change is high if densities greater than this
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23. Conclusion Current policy (1 m radius)
Appropriateness of the free growing status at 1 m radius is conservative
2500 sph exceeds the current allowable free-growing maximum (1000 sph aspen)
Spruce-birch mixedwood experiment also showed the threshold limit was sph
Now its time to rethink about the BC free-growing guideline
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24. Conclusion Consequence of current policy
Administrative vegetation control
Unnecessary cost for density management
Reduced diversity
Potential productivity reduced
Final recommendations
Leave more broadleaf competition
Reduced management cost
Potential productivity increases
Greater structural diversity
Greater species diversity
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25. Acknowledgements Funding provided by
Ministry of Forests and Range, British Columbia
FRBC-Slocan Mixedwood Chair
Carrier Lumber
Technical support provided by
Peter Fielder
Phil Comeau
Cindy Baker
Nicole Balliet
Jennifer Lange
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26. For further communication
Prof. Dr. Christopher .D.B. Hawkins
Yukon Research Centre
Yukon College
P.O. Box 2799
Whitehorse, YT, Canada Y1A 5K4
Phone:
FAX:
Dr. Amalesh Dhar
Mixedwood Ecology and Management Program
University of Northern British Columbia
3333 University Way, Prince George,
BC, Canada V2N 4Z9
Phone:
Fax:
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