8th North American Forest Ecology Workshops, USA 2011

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

Outline

1. Introduction
2. Objectives
3. Materials and Methods
4. Result
5. Conclusion


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


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


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


Materials and Method



Location:

Untreated
Canada

USA
Herbicide Treated

USA



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


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


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


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


• survey
- pre 2001
- every fall from 2001 – 2005



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



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)

Results


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



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


8 2002 2003
6
4
2
0
m
h
]
[
tH
ig
e

Treat-birch Untreat-birch Treat-spruce Untreat-
spruce


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



200
2002 2003
160

120
HDR

80

40

0
Treat-birch Untreat-birch treat-spruce Untreat-spruce


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

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

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) |
Species

Salix sp
S.roseus
A.dioicus
G.macrophyll
O.horridus

P.crista-
S.racemosa
A.margaritac
2

A.nudicaulus
A.caudatum

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


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

In total, 133 species were recorded from 2002 to 2006 but 30 % of 2002’s species were
not present in 2006


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


In total, 133 species were recorded from 2002 to 2006 but 30 % of 2002’s species were
not present in 2006


60 Herbicide Untreated Herbicide treated
50
Species Richness [S']

40

30

20

10

0
2002 2003 2004 2005 2006

Survey Year


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


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


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


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


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


Conclusion


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


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


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

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


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


8th North American Forest Ecology Workshops, USA 2011

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