1. Amalesh Dhar, Chris D. B. Hawkins
Chemical brushing for forest vegetation management in British Columbia: impact on species’ diversity, growth and White pine weevil attack
Amalesh Dhar, Chris D. B. Hawkins
Mixedwood Ecology and Management Program
University of Northern British Columbia, BC
6/15/2018
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2. Outline 1. Introduction 2. Objectives 3. Materials and Methods
4. Result
5. Conclusion
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3. Introduction Some points about BC Forest
reforestation policies and regulations are conifer-biased
broadleaves species are routinely removed from plantations
- paper birch
- trembling aspen
- black cottonwood
broadleaf species must be less than 1000 sph
practice has been consistently applied across much of Canada
all broadleaves vegetation treated as a competitor
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4. Reason for vegetation control:
Introduction
Reason for vegetation control:
to maintain BC 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 treatments applied
avoid administrative delays to get
responsibility of the stand management
all broadleaves vegetation treated as a competitor
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5. Objectives Objectives
Determine the longer term impacts of chemical brushing on:
crop or target tree growth
competitor tree growth
white pine weevil attack
non tree vegetation dynamics
- species diversity of plant community
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6. Materials and Method Location: Sinclair Mills, Prince George, BC
Zone: SBSv1, latitude 54°01’60” N, long. 121°38’20” W,
Elevation: 710 m asl
Mean annual precipitation: 900 – 1635 mm
Mean annual temperature: 1.3 – 4 °C
USA
Canada
Untreated
Herbicide Treated
sub boreal spruce very wet and cool biogeoclimatic subzone
mean annual precipitation 900 – 1635 mm of which two-thirds falls as snow
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7. Materials and Method Site preparation Total area 90 ha
- herbicide treated area – 65 ha
- herbicide untreated area – 25 ha
• Clear-cut – 1987/88
• Broadcast burn – 1988
• Planted – 1989
Glyphosate herbicide applied
- 6 L ha-1
Plot establishment
- 38 treatment units 70 m X 70 m
- measurement units 30 m X 30 m 7
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8. Materials and Method Experimental design and Survey
Overstory Vegetation survey 2002 and 2003
- plot size = 5.64 m radius (100 m2)
- 15 herbicide treated plot
- 13 herbicide untreated plot
- all conifer and broadleaf trees within a PSP were measured
- diameter at the root collar or diameter at breast height (DBH)
- tree height
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9. Materials and Method White pine weevil (WPW) Survey
• by noting trees with the characteristic of sheppard’s crook or major stem deformities
- Pre 2001
- every fall from 2001 – 2005
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10. Materials and Method Understory vegetation survey from 2002 to 2006
plot size - 1 m X 1m quadrates total (28)
- 5 m away at 45 degrees from each of the PSP centre
- surveys were conducted by the same people in all five years
Species diversity assessment
species richness (S)
species-abundance curves
alpha diversity
shannon diversity (H’)
shannon evenness (J’)
simpson’s diversity (1/D)
simpson’s evenness (E1/D)
beta diversity (between treatment diversity )
sorensen’s quantitative index (CN)
modified version of the Morisita-Horn index (CMH)
established 5 m away at 45 degrees from PSP centre posts to facilitate repeat sampling in subsequent years
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11. Results: Overstory Vegetation
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12. Results: Overstory Vegetation
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13. Results: Overstory Vegetation
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14. Results: Overstory Vegetation
White Pine Weevil Attack (Why)
significantly greater in herbicide treated area
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15. Results: Understory Vegetation
Relative abundance in 2002
Herbicide untreated
Herbicide treated
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16. Results: Understory Vegetation
Relative abundance in 2006
Herbicide untreated
Herbicide treated
In total, 133 species were recorded from 2002 to 2006 but 30 % of 2002’s species were not present in 2006
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17. Results: understory Vegetation
more early successional/pioneer species and weedy species in treated area
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18. Results: understory Vegetation
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19. Results: understory Vegetation
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20. Results: understory Vegetation
Summary of non-parametric analysis for Alpha diversity
Shannon
Simpson
Critical Value = 0, k = 2, d.f. = 1
2002
2003
2004
2005
2006
Mann-Whitney U
Diversity index 5 6 3 4 7 1
P- value
0.827
0.513
0.275
0.127
Evenness 9
7.5
0.105
0.05
0.184
0.830
0.510
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21. Beta Diversity indices [β]
Results: understory Vegetation
Summary of beta diversity
Beta Diversity indices [β]
Survey year
2002
2003
2004
2005
2006
Sorensen
0.60
0.62
0.64
0.61
Morisita-Horn
0.73
0.81
0.80
0.84
Summary of non-parametric analysis
Sorensen
Morisita-Horn
Critical Value = 5.99, k = 3, d.f. = 2
2002
2003
2004
2005
2006
Kruskal-Wallis H
4.356
2.222
6.006
5.600
5.422
4.267
2.489
5.956
P- value
0.113
0.329
0.05
0.061
0.071
0.118
0.288
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22. No volume difference between treatments
Conclusion
Impact on Growth
No volume difference between treatments
No significant difference in DBH
Height difference is significant and greater in untreated area
Not impacted by birch up to 4300 sph of birch
Impact of White Pine Weevil Attack
WPW attack significantly reduced
• Wood quality lessened
Herbicide spruce significantly shorter
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23. Conclusion Impact on understory vegetation
Species’ richness and alpha diversity were similar between treatments
- no significant difference in alpha diversity
between treatments
between years
Beta diversity was relatively low indicating little treatment effect
Higher incidence of pioneer and weedy species in herbicide treatment
Herbicide reduced structural diversity
Overall Herbicide did not affect diversity indices
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24. Final Remark (need more information) Glyphosate application:
Conclusion
Final Remark (need more information)
Glyphosate application:
- does not remove all birch
- showed minimal or no impact on herb and shrub layer
Final recommendations
reduce broadcast use of herbicide
- spot vegetation control more appropriate
- reduce financial investment
- positive impact on diversity
identify the thresholds broadleaf density that has no impact on conifer growth
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25. Acknowledgements Funding provided by Forest Renewal British Columbia
FRBC-Slocan Mixedwood Chair
Forest Investment British Columbia
Technical support provided by
Kim Menounos Anne Cole
Tracy Murray Cindy Baker
Todd Bondaroff Chris Maundrell
Nicole Balliet Kari Bondaroff
Katie Krc
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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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