Effects of Clearcut Harvesting
&
Alternative Vegetation Management
on
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
Specials thanks to:
D.A. Buckley
Canadian Forest Service
Sault Ste. Marie, Ontario, Canada
Retired
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:
PHOTOSYNTHETIC RADIATION AT 2 m
3000
PAR (uMOL . S-1 . M-2)
2600
2200
1800
1400
1000
600
200
-200
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
Results:
• Lower PAR & higher RH were observed for
the unharvested forest (F) compared with
the clearcut control (C)
PHOTOSYNTHETIC RADIATION AT 2 m
3000
PAR (uMOL . S-1 . M-2)
2600
2200
1800
1400
1000
600
200
-200
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
PHOTOSYNTHETIC RADIATION AT 0.25 m
2800
PAR (uMOL . S-1 . M-2)
2200
1600
1000
400
-200
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
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
PHOTOSYNTHETIC RADIATION AT 2 m
65
55
PAR (M-2 . D-1)
45
35
25
15
5
-5
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
PHOTOSYNTHETIC RADIATION AT 0.25 m
45
PAR (MOL . M-2 . D-1)
35
25
15
5
-5
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
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
MINIMUM RELATIVE HUMIDITY AT 2 m
100
90
HUMIDITY (%)
80
70
60
50
40
30
20
10
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
MINIMUM RELATIVE HUMIDITY AT 0.25 m
110
HUMIDITY (%)
90
70
50
30
10
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
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 nonwoody vegetation was dominant (J. Sust.
For. 10, No. 3/4, 2000, pp. 267-275)
MAXIMUM AIR TEMPERATURE AT 2 m
36
TEMPERATURE (o C)
32
28
24
20
16
12
8
4
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
MAXIMUM AIR TEMPERATURE AT 0.25 m
40
TEMPERATURE (o C)
34
28
22
16
10
4
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
MINIMUM AIR TEMPERATURE AT 2 m
30
TEMPERATURE (o C)
25
20
15
10
5
0
-5
-10
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
MINIMUM AIR TEMPERATURE AT 0.25 m
AIR TEMPERATURE (o C)
22
16
10
4
-2
-8
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
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
MAXIMUM SOIL TEMPERATURE AT 15 cm
19
TEMPERATURE (o C)
17
15
13
11
9
7
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
MAXIMUM DUFF TEMPERATURE (5 cm)
26
TEMPERATURE (o C)
22
18
14
10
6
2
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
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 longerlasting 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
MAXIMUM RELATIVE HUMIDITY AT 2 m
102
98
HUMIDITY (%)
94
90
86
82
78
74
70
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
MAXIMUM RELATIVE HUMIDITY AT 0.25 m
104
HUMIDITY (%)
100
96
92
88
84
80
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
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
MINIMUM SOIL TEMPERATURE AT 15 cm
17
TEMPERATURE (o C)
15
13
11
9
7
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
MINIMUM DUFF TEMPERATURE (5 cm)
22
TEMPERATURE (o C)
18
14
10
6
2
-2
JUN 2
JUL 11
AUG 20
1998
SEP 29
FOREST
CONT ROL
BRUSHSAW
GLYPHOSAT E
Minimum Soil Temperature (o C)
Location FOR
CON
BRU
GLY
15 cm
12.9 ab 12.4 b 13.2 a 13.3 a
Duff
12.8 a 12.0 ab 11.3 b 12.4 a