1. Chemical brushing for forest vegetation management in
British Columbia: impact on species’ diversity,
growth and White pine weevil attack
Amalesh Dhar and Chris D. B. Hawkins
Mixedwood Ecology and Management Program
University of Northern British Columbia, BC
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 1

2. Outline
1. Introduction
2. Objectives
3. Materials and Methods
4. Result
5. Conclusion
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 2

3. Introduction
Some points about BC Forest
• historically BC reforestation policies and regulations are conifer-biased
• broadleaves species (birch, aspen) are routinely removed from plantations
- for maximizing crop tree growth
• broadleaf species must be less than 1000 sph
• practice has been consistently applied across much of Canada
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 3

4. Introduction
Vegetation management in BC:
• 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
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 4

5. Objectives
Objectives
• Determine the impacts of chemical brushing on:
i) crop or target tree growth
ii) competitor tree growth
iii) white pine weevil attack
• Long term impact on non tree vegetation dynamics
- species diversity of plant community
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 5

6. Materials and Method
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 6

7. Materials and Method
Location:
Untreated
Canada
USA
Herbicide Treated
USA
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 7

8. Materials and Method
Location :
Sinclair Mills, Prince George, BC, Canada
Zone: SBSv1, wet and cool
Latitude: 54°01’60” N
Longitude: 121°38’20” W
Elevation: 710 m asl
Mean annual precipitation: 900 – 1635 mm (two-thirds falls as snow)
Mean annual temperature: 1.3 – 4 °C
Stand Age at plot establishment: 13 year-old stand
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 8

9. Materials and Method
Site preparation
Total area 90 ha
- herbicide treated area – 25 ha
- herbicide untreated area – 65 ha
• Clear-cut – 1987/88
• Planted – 1989
•Glyphosate herbicide applied - 1996
- 6 L per ha
• Plot establishment - 2002 Untreated
- total 38, 70 m X 70 m treatment units
Herbicide Treated
- further 30 m X 30 m measurement units
installed in the center of the treatment plot
9
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins

10. Materials and Method
Survey : Overstory Vegetation
• survey year 2002 and 2003
• plot size - 5.64 m radius (100 m2)
• no. PSP for herbicide treated - 15
• no. PSP for herbicide untreated – 13
• DBH and height of all conifer and broadleaf trees within a PSP were
measured
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 10

11. Materials and Method
White pine weevil (WPW) [Pissodes strobi (Peck)]
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 11

12. Materials and Method
White pine weevil (WPW) [Pissodes strobi (Peck)]
terminal leaders
• by noting trees with the characteristic of
Sheppard’s crook or major stem deformities
- kills the previous year's growth
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 12

13. Materials and Method
White pine weevil (WPW) [Pissodes strobi (Peck)]
• survey
- pre 2001
- every fall from 2001 – 2005
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 13

14. Materials and Method
Understory vegetation survey
• survey year from 2002 to 2006
• plot size - 1 m X 1m quadrates
- 5 m away at 45 degrees of each sky direction at each PSP
- plant species were identified according to MacKinnon et al.
(1999) and Cranston et al. (1996)
- visual estimate of vegetation percent cover was recorded
- surveys were conducted by the same people in all five years
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 14

15. Materials and Method
Understory vegetation survey
• species diversity assessment
• species richness (S)
• species-abundance curves
• alpha diversity (Magurran 1988)
- shannon diversity (H’)
- shannon evenness (J’)
- simpson’s diversity (1/D)
- simpson’s evenness (E1/D)
• beta diversity (between treatment diversity) (Magurran 2004)
- sorensen’s quantitative index (CN)
-modified version of the Morisita-Horn index (CMH)
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 15

16. Results
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 16

17. Results: Overstory Vegetation
5000 Spruce Birch
4000
Tree /ha
3000
2000
1000
0
Treated Untreated
Treatment
Stocking in herbicide treated and untreated area in 2003
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 17

18. Results: Overstory Vegetation
10 2002 2003
8
6
DBH [ cm ]
4
2
0
Treat-birch Untreat-birch treat-spruce Untreat-spruce
Species and treatment
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 18

19. Results: Overstory Vegetation
8 2002 2003
6
4
2
0
m
h
]
[
tH
ig
e
Treat-birch Untreat-birch Treat-spruce Untreat-
spruce
Species and treatment
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 19

20. Results: Overstory Vegetation
0.015 2002 2003
0.012
]
-3
0.009
0.006
0.003
m
e
[V
lu
o
0
Treat-birch Untreat-birch Treat-spruce Untreat-spruce
Species and treatment
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 20

21. Results: Overstory Vegetation
200
2002 2003
160
120
HDR
80
40
0
Treat-birch Untreat-birch treat-spruce Untreat-spruce
Species and treatment
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 21

22. Results: Overstory Vegetation
White Pine Weevil Attack
80 Herbicide Untreated
60
WPW attack [%]
40
20
0
Pre 2001 2001 2002 2003 2004 2005
Survey year
• significantly greater in herbicide treated area
• overhead shading in untreated area (Taylor et al. 1996)
• females WPW select vigorously terminal leaders for brood (Alfaro 1995)
• lower densities enable weevils to more easily locate terminal leaders
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 22

23. RA [%]
04/09/13
10
12
0
2
4
6
8
C.canadensis
H.umbelatum
Brachy sp.
Herbicide treated 2002
Dicranum spp
Grass sp
R.parviflorus
T. officinale
R. idaeus
E. angustifolia
G. triflorum
P. crista-
T. trifoliata
P. glauca x
V.canadensis
A.margaritace
Mixedwood Ecology and Management Program (UNBC) |
E. arvense
[black line is fitted curve and other one is real data]
Species
C. arvense
G. dryopteris
M. nuda
R. lacustre
Results: Understory Vegetation
Salix sp
S. racemosa
A. rubra
A. alnifolia
2
Relative species abundance (%) of herbicide untreated and treated areas
A.conspicuou
Amalesh Dhar, Chris D.B. Hawkins
A.modestus
y = 11.497e
A.filix-femina
R = 0.9679
C. rangifering
23
-0.1069x
G.macrophyll
T.heterophyll

24. RA [%]
04/09/13
0
4
8
12
C.canadensi
Brachy sp.
A.filix-femina
R.parviflorus
E.angustifolia
Herbicide untreated 2002
H.aurantiacu
T.trifoliata
G.triflorum
Grass sp
G.dryopteris
Dicranum
Plagiomnium
T.officinale
E.arvense
V.canadensi
A.modestus
C.arvense
R.idaeus
Mixedwood Ecology and Management Program (UNBC) |
[black line is fitted curve and other one is real data]
Species
Salix sp
S.roseus
A.dioicus
G.macrophyll
O.horridus
Results: Understory Vegetation
P.crista-
S.racemosa
A.margaritac
2
A.nudicaulus
A.caudatum
Relative species abundance (%) of herbicide untreated and treated areas
A.conspicuou
y = 9.7478e
Amalesh Dhar, Chris D.B. Hawkins
D.hookeri
R = 0.9645
H.umbelatum
-0.0935x
M.dilatatum
P.trichocarpu
24
S.racemosa
S.amplexifoli

25. Results: Understory Vegetation
Herbicide treated 2006
10 y = 7.1157e-0.0697x
8 R2 = 0.9509
6
4
2
0
1 6 11 16 21 26 31 36 41 46
Relative species abundance (%) of herbicide untreated and treated areas
[black line is fitted curve and other one is real data]
In total, 133 species were recorded from 2002 to 2006 but 30 % of 2002’s species were
not present in 2006
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 25

26. Results: Understory Vegetation
Herbicide untreated 2006
10 y = 5.857e-0.0612x
8 R2 = 0.9437
6
4
2
0
1 6 11 16 21 26 31 36 41 46 51 56
Relative species abundance (%) of herbicide untreated and treated areas
[black line is fitted curve and other one is real data]
In total, 133 species were recorded from 2002 to 2006 but 30 % of 2002’s species were
not present in 2006
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 26

27. Results: Understory Vegetation
60 Herbicide Untreated Herbicide treated
50
Species Richness [S']
40
30
20
10
0
2002 2003 2004 2005 2006
Survey Year
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 27

28. Results: Understory Vegetation
Alpha diversity
4 Treated Untreated
3.5
3
2.5
2
1.5
1
H
S
o
n
h
a
']
[
0.5
0
2002 2003 2004 2005 2006
Survey year
Summary of Shannon diversity (H’) from 2002 to 2006
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 28

29. Results: Understory Vegetation
Alpha diversity
1 Treated Untreated
0.8
0.6
0.4
S
o
n
h
0.2
J
a
']
[
0
2002 2003 2004 2005 2006
Survey year
Summary of Shannon evenness (J’) from 2002 to 2006
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 29

30. Results: Understory Vegetation
Alpha diversity
1 Treated Untreated
0.8
Simpson [E1/D]
0.6
0.4
0.2
0
2002 2003 2004 2005 2006
Survey year
Summary of Simpson‘s evenness (E1/D) from 2002 to 2006
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 30

31. Results: Understory Vegetation
Alpha diversity
30 Treated Untreated
25
20
15
10
m
D
S
n
o
p
1
s
5
]
[
/
i
0
2002 2003 2004 2005 2006
Survey year
Summary of Simpson's diversity (1/D) from 2002 to 2006
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 31

32. Results: Understory Vegetation
Summary of beta diversity
Beta Diversity Survey year
indices [β] 2002 2003 2004 2005 2006
Sorensen 0.60 0.62 0.64 0.61 0.60
Morisita-Horn 0.73 0.81 0.80 0.84 0.61
Summary of non-parametric analysis
Sorensen Morisita-Horn
Critical Value = 5.99, k = 3, d.f. = 2
2002 2003 2004 2005 2006 2002 2003 2004 2005 2006
Kruskal-Wallis H 4.356 2.222 6.006 5.600 5.422 4.267 2.489 5.600 5.956 4.267
P- value 0.113 0.329 0.05 0.061 0.071 0.118 0.288 0.061 0.05 0.118
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 32

33. Conclusion
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar & Chris D.B. Hawkins 33

34. Conclusion
Impact on Growth
 No volume difference between treatments
 No significant difference in DBH
 spruce height difference was not significant but greater in untreated area
 Not impacted by birch up to 4300 sph of birch
Impact of White Pine Weevil Attack
 significant difference between treatment
 greater number of stem defects in treated area
 reduce wood quality
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 34

35. 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
 Herbicide reduced structural diversity
 Overall herbicide did not affect diversity indices
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 35

36. Conclusion
Final Remark:
 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
 finally the BC free to grow standard need to reconsider
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 36

37. 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
04/09/13 Mixedwood Ecology and Management Program (UNBC) | Amalesh Dhar, Chris D.B. Hawkins 37

38. For further communication
Prof. Dr. Christopher .D.B. Hawkins Dr. Amalesh Dhar
Yukon Research Centre Mixedwood Ecology and Management Program
Yukon College University of Northern British Columbia
P.O. Box 2799 3333 University Way, Prince George,
Whitehorse, YT, Canada Y1A 5K4 BC, Canada V2N 4Z9
Phone: +1 867 456-8627 Phone: +1 250 960 5778
FAX: +1 867-456-8672 Fax: +1 250 960 5339
Email: chawkins@yukoncollege.yk.ca Email: dhar@unbc.ca
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