Anthropogenic influences on the subsurface temperatures: Land-use changes

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Anthropogenic influences on the subsurface
temperatures Land-use changes

• Daniela Nitoiu and Hugo Beltrami
• Environmental Sciences Research Center
• St. Francis Xavier University
• Antigonish, Nova Scotia, Canada

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Outline

• 1. Introduction
• 2. Objective
• 3. Methodology
• 3.1. Synthetic example
• 3.2. Real example
• 4. Discussion and Conclusions

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1. Introduction
Increase of the surface heat flux in the
deforested area
Increase of the GST in the deforested area
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1. Introduction (continuation)
Forested site
Clear-cut site
Myette et al., unpublished data
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1. Introduction (continuation)
Forest floor thermal properties
Soil thermal properties ?s 3 Wm-1K-1, ?s
110-6 m2s-1. Cermak and Rybach, 1982
Forest floor thermal properties ?o 0.142
0.019 Wm-1K-1, ?o 0.108 0.003 10-6
m2s-1. ESRC, unpublished data
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1. Introduction (continuation)
Variation of the forest floor organic matter
after deforestation (after Covington, 1981)
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2. Objective
To find a method to correct suitable borehole
temperature data for the effects of deforestation.
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3. Methodology
Heat propagation into the ground is based on
? the subsurface is perfectly conductive, ?
there is no lateral propagation of the heat.
One-dimensional heat conduction equation
T(z,t) temperature, k(z) thermal
diffusivity, z depth, t time.
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3. Methodology (continuation)
GST following deforestation

• Tg AtBeCt T0 ,
• Tg - the ground surface temperature
• A, B, C, D coefficients (Covington, 1981)
• A5.25 (0C/year) B1.24 C-0.0649 (1/year)
  D1.063
• T0 - the ground surface temperature before
  deforestation
• t - time in years since deforestation.

D
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3. Methodology (continuation)
GST variation after deforestation



(K)
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3. Methodology (continuation)
3.1. Synthetic example
Synthetic control Deforestation
30y.b.p. Deforestation 120y.b.p.
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3.1. Synthetic example (continuation)
Synthetic control Synthetic corrected for
deforestation (30Y.B.P.) Synthetic corrected for
deforestation (120Y.B.P.)
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3.1. Synthetic example (continuation)
Synthetic control Synthetic corrected for
deforestation (30y.b.p.) Synthetic corrected for
deforestation (120y.b.p.)
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3. Methodology (continuation)
3.2. Real example
The borehole site was deforested 34 years before
temperature logging.
uncorrected corrected
Data from http//www.geotop.uqam.ca/geotop/geophy
sique/flux/index.htm
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3.2. Real example (continuation)
uncorrected corrected
Similar warming trends were found by
Guillou-Frottier et al. (1998) and Gosselin and
Mareschal (2003) in central Canada.
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4. Discussion and Conclusions
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4. Discussion and Conclusions (continuation)
6) harvesting evenaged or un-evenaged
1) natural regeneration or planting
2) manual weeding or herbicide treatment
5) shelterwood or regeneration harvests
3) Release spacing
4) Commercial thinning
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4. Discussion and Conclusions (continuation)
Pictures provided by the Environmental Sciences
Research Center staff.
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4. Discussion and Conclusions (continuation)
Deforestation situations
4 bare ground, 3 grassland, 2 different
forest, 1 similar forest with the
pre-harvesting one.
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Conclusions
? Geothermal data are affected by deforestation
but they can be corrected ? Desired method
an energy balance vegetation soil
processes model ? Correction of the
contaminated data ? incorporation in global
borehole climatology database ? Reexamination
of the contaminated data already included
in the global borehole climatology data base.
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This research is funded by
CFCAS
NSERC
AIF
CFI
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3.2. GSHF variation
GSHF variation after deforestation
l
2 ?
?
ql
(Tk1-Tk)(vl-k1 - vl-k )
vp k ?t
k1
(Beltrami, 2001)
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3.2. GSHF variation (continuation)
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1. Introduction (continuation)
Forest soil profile
Clear-cut soil profile
Pictures provided by the Environmental Sciences
Research Center staff.
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3.4. Real example (continuation)
1930-1980
Beltrami and Bourlon, EPSL, 2004 in press.