Boreal Mixedwoods Conference, Canada 2012
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Transcript of Boreal Mixedwoods Conference, Canada 2012
104/10/23
Christopher D.B. Hawkins and Amalesh Dhar Mixedwood Ecology and Management Program
University of Northern British Columbia, BC
Impact of variable broadleaf density on spruce growth near Dawson Creek and Fort Nelson in northern
British Columbia
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
204/10/23
Outline
1. Traditional woodlands (forest) management in central BC
2. Why Mixedwoods?
3. Objectives
4. Materials and Methods
5. Results
6. Conclusion
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
304/10/23
Introduction
Traditional woodlands (forest) management in central BC:
• Historically BC reforestation policies and regulations are conifer-biased
• Broadleaves species (birch, aspen) are routinely removed from plantations
- maximize conifer 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”
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
404/10/23
Introduction
Traditional woodlands (forest) management in central BC:
• Stands may only be declared free to grow when 2/3 years have passed since chemical or manual brushing treatment applied
• Avoid administrative delays to revert stand management responsibility back to Crown
• Broadleaf species must be less than 1000 stems ha-1
• Practice has been consistently applied across much of Canada
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
504/10/23
Introduction
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
604/10/23
Mechanisms for increased complex stand productivity:
b) Complementary interactions (Species that differ in shade tolerance, height growth
rates, crown structure, phenology and rooting depth)
- Rate inter-specific competition is lower than intra-specific
Betula – Picea mixtures in Scandinavia
• Forest health [WPW attack reduced at increased deciduous density (Hawkins et al.2012)]
• better able to deal with disturbances and have greater ecological stability than pure stand
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
704/10/23
Objectives
• examine the growth response of spruce to different brushing treatments
as well as varying levels broadleaf (birch & aspen) densities
• test the effectiveness of current BC free-growing criteria
Objectives
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
804/10/23Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Materials and Methods
904/10/23
Materials and Methods
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Site: Fort Nelson (Prophet & Slocan)
Location: Northeastern British Columbia
Zone: BWBS mw2-Dominated by broadleaf (Birch) – conifer (Spruce)
forests and conifer forests
Climate:
Snow: Any time
Mean annual precipitation: 330 – 570 mm (30-40% falls as snow)
Mean annual temperature: -1.4 °C (extremes -51.7 °C, 36.7 °C)
Site : Dawson Creek (One Island Lake)
Location: Northern BC
Zone: BWBS mw1
- Dominated by broadleaf (Aspen) – conifer (Spruce) forests and conifer forests
Climate:
Precipitation: 556 mm (35% falls as snow)
Temperature: 1.8°C (extremes – 43.8°C, 34.5 °C)
1004/10/23
Materials and Methods
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
1104/10/23
Materials and Methods
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Temporary sample plots (TSP): One island lake & Prophet
•A systematic grid point was established on each stand at 100 meter interval - the closest undamaged spruce was selected as a target tree and plot centre or- go to nearest spruce in cardinal direction
• Plot radius of TSP: 1.78 m (area: 0.001ha or 10 m2)• Measure what is there (no treatments were initiated)• Height and DBH of target spruce were measured from each TSP• All TSP’s were re-measured in 2009
Experimental design and data collection Two types of sample plots were established
1204/10/23
Permanent sample plots (PSP) (all three sites)
A single tree variable brushing radius experiment was established• target spruce tree was selected as like TSP• a brush-free radius of 0 m, 1 m, 2 m or 4 m was
established around each spruce• prior to brushing, all broadleaf and spruce stems within
the radius were measured (height and DBH)•All PSP’s were re-measured in 2009
Materials and Methods
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Control / 0m radius
1m radius
2m radius
4m radius
1304/10/23
Materials and Methods
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Establishment year
Area Target species
Competitive species
TSP PSP Stand Age
Re-measurement
2007 One Island Lake Spruce Aspen 82 66 14 2009
2007 Slocan Spruce Birch 0 68 17 2009
2007 Prophet Spruce Birch 72 79 16 2009
Relative density index: often used to determine the growth of trees (Ducey & Larson 2003)
Where,
Where, BA = Basal area m2 ha-1, QDM = quadratic mean diameter in cm, 0.4 = a single slope coefficient from Curtis (1982).
4.0)(QMD
BARDI
•Competition index:
- Broadleaf density and relative density index
1404/10/23Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Results
1504/10/23Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Results: Permanent sample plots
0
2
4
6
8
10
0 1 2 4
Plot radius [m]
Plo
t es
tab
lish
DB
H [
cm]
one island Slocan Prophet
Establishment spruce DBH(± SEM) by plot radius at three forest stands
1604/10/23
Results: Permanent sample plots
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Relationship between establishment DBH and aspen density
- Relationship was significant
y = -0.0001x + 6.9944
R2 = 0.172
0
2
4
6
8
10
0 5000 10000 15000 20000
Aspen density at plot estab. [stems ha-1]
DB
H a
t p
lot
esta
b. [
cm]
One island lake
1704/10/23
Results: Permanent sample plots
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
y = -0.0601x + 5.7533
R2 = 0.0466
0
2
4
6
8
10
1 3 5 7 9 11 13 15
Aspen RDI at plot establishment
DB
H a
t p
lot
es
tab
. [c
m]
Relationship between establishment DBH and aspen RDI
- Relationship was not significant
One island lake
1804/10/23Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Results: Permanent sample plots
Slocan
y = -5E-05x + 7.0128
R2 = 0.0055
0
2
4
6
8
10
12
0 2000 4000 6000 8000 10000 12000
Birch desnity at plot estab. [stems ha-1]
DB
H a
t p
lot
esta
b.
[cm
]
Relationship between establishment DBH and birch density
- Relationship was not significant
1904/10/23Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Results: Permanent sample plots
Prophet
y = -0.0004x + 8.8425
R2 = 0.0618
0
5
10
15
0 2000 4000 6000 8000 10000
Birch density at plot estab. [stems ha-1]
Sp
ruce
DB
H a
t p
lot
esta
b.[
cm]
Relationship between establishment DBH and birch density based
-relationship was also not significant
0
0.4
0.8
1.2
0 1 2 4
Plot radius [m]
MG
I [cm
]
One island Slocan Prophet
2004/10/23Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
• MGI same at 0 (control), 1 and 2 m radii and increased in 4m radius
• MGI growth - significantly differed at One island & Slocan
- not significantly different at prophet
Results: Permanent sample plots
Mean annual DBH increment (± SEM) by plot radius at three forest stands
iiB
iiB
ab i
A a
ab
ii
Bb
Site F P(F) R2
One Island 5.132 0.003 0.20
Slocan 3.861 0.013 0.15
Prophet 2.296 0.085 0.28
2104/10/23Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Results
Temporary sample plots (TSP)
2204/10/23Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
• Similar spruce DBH up to 4000 stem ha-1
Results: Temporary sample plots
One island lake
0
2
4
6
8
0 1000 2000 3000 4000 5000 6000 7000 > 8000
Aspen density [stems ha-1]
Sp
ruc
e p
lot
es
tab
. DB
H [
cm
] Spruce Aspen
2304/10/23Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Results: Temporary sample plots
• Similar spruce DBH up to 6000 except density group 5000 stems ha-1
Prophet
0
2
4
6
8
10
0 1000 2000 3000 4000 5000 6000 7000 >8000
Birch density [stems ha-1]
Sp
ruc
e p
lot
es
tab
. DB
H[c
m] Spruce Birch
2404/10/23Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Results: Temporary sample plots
y = -2E-05x + 0.7257
R2 = 0.1797
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000
Aspen density [stems ha-1]
Mea
n a
nn
ual
DB
H g
row
th
[cm
]
• Aspen density ≥ 10000 stems ha-1 siginificantly impacted the spruce DBH growth
One island lake
2504/10/23Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
• Aspen RDI ≥ 6 siginificantly impacted the spruce DBH growth
Results: Temporary sample plots
y = -0.0442x + 0.8075
R2 = 0.3227
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 2 4 6 8 10
Aspen RDI
Mea
n a
nn
ual
DB
H g
row
th [
cm]
One island lake
2604/10/23Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Results: Temporary sample plots
y = -5E-05x + 0.9124
R2 = 0.294
00.20.40.60.8
11.21.41.6
0 2000 4000 6000 8000 10000
Birch density [stems ha-1]
Mea
n a
nn
ual
DB
H g
row
th
[cm
]
Prophet
• Birch density ≥ 5000 stems ha-1 siginificantly impacted the spruce DBH growth
2704/10/23Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Results: Temporary sample plots
Prophet
y = -0.0304x + 0.8051
R2 = 0.0678
00.20.4
0.60.8
11.2
1.41.6
0 1 2 3 4 5 6 7 8
Birch RDI
Mea
n a
nn
ual
DB
H g
row
th
[cm
]
RDI ≥ 5 siginificantly impacted the spruce DBH growth
2804/10/23
Conclusion
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
2904/10/23
Conclusion
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Broadleaf competition not as severe as previously thought
DBH unaffected across a range of deciduous densities
MGI was same at control, 1 and 2 m brushing radii and only increased at
4 m
It assumed threshold densities much greater than the hypothesized
(>1000 stem ha-1) density that significantly reduced crop tree growth
Greater structural and species diversity
3004/10/23
Consequence of current policy Administrative vegetation control
Unnecessary cost for density management Reduced diversity Potential productivity reduction brushing does not remove all broadleaf (Hawkins et al. 2012)
Conclusion
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
Final recommendations Leave more broadleaf competition
May reduced management cost Potential productivity increases Greater structural diversity Greater species diversity If risk is considered, mixed stands are a viable investment
3104/10/23
• Funding provided byMinistry of Forests and Range, British ColumbiaFRBC-Slocan Mixedwood Chair
• Technical support provided byKyle Runzer Cindy BakerNicole BallietEduardo Bittencourt
Acknowledgements
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
3204/10/23
Dr. Amalesh DharMixedwood Ecology and Management ProgramUniversity of Northern British Columbia3333 University Way, Prince George, BC, Canada V2N 4Z9Phone: +1 250 960 5778Fax: +1 250 960 5339Email: [email protected]
Christopher .D.B. HawkinsYukon Research CentreYukon CollegeP.O. Box 2799Whitehorse, YT, Canada Y1A 5K4Phone: +1 867 456-8627FAX: +1 867-456-8672Email: [email protected]
For further communication
Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar
3304/10/23Mixedwood Ecology and Management Program (UNBC) | Christopher D.B. Hawkins & Amalesh Dhar