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Effects of Clearcut Harvesting&
Alternative Vegetation Managementon
Forest Microclimate
P.E. Reynolds
Canadian Forest Service
Sault Ste. Marie, Ontario, Canada
Cooperators
Ontario Forest Research Institute:
R.A. Lautenschlager & F.W. Bell
&
University of Guelph:
A.M. Gordon, J.A. Simpson, & D.A. Gresch
Objectives:
• To quantify treatment-related microclimatic differences resulting from harvesting & alternative vegetation management practices
• To assess the duration of these differences
Treatments:
• Unharvested forest (F) blocks -- 100 yrs; aspen, fir, white birch
• Clearcut control (C) -- harvested 1986 through 1988; planted with spruce
• 2 alternative herbicides, glyphosate (G) & triclopyr (T), applied August 1993
• 2 alternative cutting methods, brushsaws (B) & Silvana mower (S), September 1993
Methods:• Vegetation treatments applied to 4 clearcut
blocks (30-60 ha each).
• Weather stations established in F, C, B, and G treatments on 3 blocks 1994-1998
• Programmed to continuously monitor PAR, RH, & air temperatures at 0.25 & 2.0 m above forest floor & soil temps at 5 & 15 cm
• Repeated measures ANOVA on 5th yr data
Results:
• Are based upon daily measurements of PAR, air & soil temperatures, & RH for the period Jun 2 through October 14, 1998
• Data are means for 2 replicate blocks
• 5 years after B & G treatments
• 12 years after harvesting
• Significant treatment differences for 20 of 22 measured parameters
Lines fitted to data for viewing:
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
PHOTOSYNTHETIC RADIATION AT 2 m
1998
PA
R (
uM
OL
. S
-1 .
M-2
)
-200
200
600
1000
1400
1800
2200
2600
3000
JUN 2 JUL 11 AUG 20 SEP 29
Results:
• Lower PAR & higher RH were observed for the unharvested forest (F) compared with the clearcut control (C)
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
PHOTOSYNTHETIC RADIATION AT 2 m
1998
PA
R (
uMO
L . S
-1 .
M-2
)
-200
200
600
1000
1400
1800
2200
2600
3000
JUN 2 JUL 11 AUG 20 SEP 29
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
PHOTOSYNTHETIC RADIATION AT 0.25 m
1998
PAR
(uM
OL
. S-1
. M
-2)
-200
400
1000
1600
2200
2800
JUN 2 JUL 11 AUG 20 SEP 29
PAR (uMol . S-1 . M-2)
Location FOR CON BRU GLY
2.0 m 619 d 789 c 1629 b 1852 a
0.25 m 395 c 437 c 699 b 1376 a
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
PHOTOSYNTHETIC RADIATION AT 2 m
1998
PA
R (
M-2
. D
-1)
-5
5
15
25
35
45
55
65
JUN 2 JUL 11 AUG 20 SEP 29
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
PHOTOSYNTHETIC RADIATION AT 0.25 m
1998
PAR
(MO
L . M
-2 .
D-1
)
-5
5
15
25
35
45
JUN 2 JUL 11 AUG 20 SEP 29
PAR (Mol . M-2 . D-1)
Location FOR CON BRU GLY
2.0 m 2.2 c 3.0 c 27.2 b 34.0 a
0.25 m 0.8 c 1.5 bc 2.5 b 18.0 a
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
MINIMUM RELATIVE HUMIDITY AT 2 m
1998
HU
MID
ITY
(%
)
10
20
30
40
50
60
70
80
90
100
JUN 2 JUL 11 AUG 20 SEP 29
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
MINIMUM RELATIVE HUMIDITY AT 0.25 m
1998
HU
MID
ITY
(%)
10
30
50
70
90
110
JUN 2 JUL 11 AUG 20 SEP 29
Minimum Relative Humidity (%)
Location FOR CON BRU GLY
2.0 m 58 a 53 b 52 b 43 c
0.25 m 55 a 49 b 46 b 40 c
Results:
• Seasonal air temperature extremes (o C), for daily highs and lows, were associated with the glyphosate (G) treatment, where non-woody vegetation was dominant (J. Sust. For. 10, No. 3/4, 2000, pp. 267-275)
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
MAXIMUM AIR TEMPERATURE AT 2 m
1998
TE
MP
ER
AT
UR
E (
o C
)
4
8
12
16
20
24
28
32
36
JUN 2 JUL 11 AUG 20 SEP 29
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
MAXIMUM AIR TEMPERATURE AT 0.25 m
1998
TE
MP
ER
AT
UR
E (
o C
)
4
10
16
22
28
34
40
JUN 2 JUL 11 AUG 20 SEP 29
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
MINIMUM AIR TEMPERATURE AT 2 m
1998
TE
MP
ER
AT
UR
E (
o C
)
-10
-5
0
5
10
15
20
25
30
JUN 2 JUL 11 AUG 20 SEP 29
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
MINIMUM AIR TEMPERATURE AT 0.25 m
1998
AIR
TE
MP
ER
AT
UR
E (
o C
)
-8
-2
4
10
16
22
JUN 2 JUL 11 AUG 20 SEP 29
Air Temperatures (o C)
Location Daily FOR CON BRU GLY
2.0 m Max 19.9 b 21.2 b 21.6 ab 22.9 a
0.25 m Max 21.0 c 21.8 bc 23.0 b 26.0 a
2.0 m Min 12.7 a 11.8 ab 10.8 b 10.8 b
0.25 m Min 11.5 a 10.3 a 8.5 b 7.8 b
Results:
• Mean seasonal soil temperatures at 15 cm depth (daily highs) remained highest for the glyphosate (G) treatment, and higher than for all other treatments
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
MAXIMUM SOIL TEMPERATURE AT 15 cm
1998
TEM
PE
RAT
UR
E (o
C)
7
9
11
13
15
17
19
JUN 2 JUL 11 AUG 20 SEP 29
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
MAXIMUM DUFF TEMPERATURE (5 cm)
1998
TEM
PE
RAT
UR
E (o
C)
2
6
10
14
18
22
26
JUN 2 JUL 11 AUG 20 SEP 29
Maximum Soil Temperature (o C)
Location FOR CON BRU GLY
15 cm 13.5 b 13.4 b 13.0 b 14.3 a
Duff 15.1 b 15.2 b 15.6 a 16.2 a
Conclusions:
• The effects of routine forestry practices in altering forest microclimate are longer-lasting than anticipated
• Changes in forest microclimate are likely contributing to global warming & to global environmental change
• The extent & significance of these contributions are yet to be determined
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
MAXIMUM RELATIVE HUMIDITY AT 2 m
1998
HU
MID
ITY
(%)
70
74
78
82
86
90
94
98
102
JUN 2 JUL 11 AUG 20 SEP 29
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
MAXIMUM RELATIVE HUMIDITY AT 0.25 m
1998
HU
MID
ITY
(%)
80
84
88
92
96
100
104
JUN 2 JUL 11 AUG 20 SEP 29
Maximum Relative Humidity (%)
Location FOR CON BRU GLY
2.0 m 92 a 91 ab 91 ab 90 b
0.25 m 98 b 98 b 99 ab 100 a
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
MINIMUM SOIL TEMPERATURE AT 15 cm
1998
TE
MP
ER
AT
UR
E (
o C
)
7
9
11
13
15
17
JUN 2 JUL 11 AUG 20 SEP 29
FOREST
CONTROL
BRUSHSAW
GLYPHOSATE
MINIMUM DUFF TEMPERATURE (5 cm)
1998
TE
MP
ER
AT
UR
E (
o C
)
-2
2
6
10
14
18
22
JUN 2 JUL 11 AUG 20 SEP 29