Effects of Clearcut Harvesting & Alternative Vegetation Management on Forest Microclimate

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

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:

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


1998

PA

R (

uMO

L . S

-1 .

M-2

)

-200

200

600

1000

1400

1800

2200

2600

3000


FOREST

CONTROL

BRUSHSAW

GLYPHOSATE

PHOTOSYNTHETIC RADIATION AT 0.25 m

1998

PAR

(uM

OL

. S-1

. M

-2)

-200

400

1000

1600

2200

2800


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


1998

PA

R (

M-2

. D

-1)

-5

5

15

25

35

45

55

65


FOREST

CONTROL

BRUSHSAW

GLYPHOSATE

PHOTOSYNTHETIC RADIATION AT 0.25 m

1998

PAR

(MO

L . M

-2 .

D-1

)

-5

5

15

25

35

45


PAR (Mol . M-2 . D-1)


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


FOREST

CONTROL

BRUSHSAW

GLYPHOSATE

MINIMUM RELATIVE HUMIDITY AT 0.25 m

1998

HU

MID

ITY

(%)

10

30

50

70

90

110


Minimum Relative Humidity (%)


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


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


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


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


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


FOREST

CONTROL

BRUSHSAW

GLYPHOSATE

MAXIMUM DUFF TEMPERATURE (5 cm)

1998

TEM

PE

RAT

UR

E (o

C)

2

6

10

14

18

22

26


Maximum Soil Temperature (o C)


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


FOREST

CONTROL

BRUSHSAW

GLYPHOSATE

MAXIMUM RELATIVE HUMIDITY AT 0.25 m

1998

HU

MID

ITY

(%)

80

84

88

92

96

100

104


Maximum Relative Humidity (%)


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


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


Minimum Soil Temperature (o C)


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

Effects of Clearcut Harvesting & Alternative Vegetation Management on Forest Microclimate

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