application of ground-penetrating-radar, electrical...
TRANSCRIPT
Application of Ground-Penetrating-Radar, Electrical Resistivity Imaging and 3D aerial photos to study paludification in northern
boreal forests of Canada
Ahmed Laamrani1,2, Osvaldo Valeria1,2, Yves Bergeron1,2 & Li Zhen Cheng1
Université du Québec en Abitibi-Témiscamingue1 , Chaire Industrielle en aménagement forestier durable2.
445 boul. de l'Université, Rouyn-Noranda (Québec) J9X 5E4
INTRODUCTION
This research attempts to link stand structure characteristics to Ground Penetrating Radar (GPR) and Electrical Resistivity
Imaging (ERI) data in order to produce very precise numerical models of the mineral slope and organic layer thickness of
nine sites (250 m x 250 m) on the Clay Belt
CONTEXTE
Black spruce forests located on the Clay Belt, a region of eastern North America, are characterized by a decline in forest productivity
Paludification leads to a significant decrease in forest productivity
Topography of the mineral soil is thoughtto have a major influence on the occurrenceof paludification
Needs for a better understanding of thefactors that reduce forest productivity :
Structure of vegetation
Degree of paludification
Relate mineral soil slope, productivity °ree of paludification
+++: Sampling paludified plots (Simard et al. 2009)
The results of this ongoing research will:
1. Allow a more accurate determination of the impacts of paludification on the landscape and on forest productivity
2. Improve forest management practices in the northern boreal forest
GPR method = Explore the shallow
subsurface
12 GPR transects will be collected with a
high-speed pulseEKKO 100 system in each site.
500 MHz antenna Investigation depth ~ 2-3 m
GPR interpretation is primarily based on
Imaging: nature & origin of reflections
Interpolate between 12 GPR by kriging 3D
model for each study site spatial variability
of organic layer thickness & mineral soil slope
UAF 85-51 &
85-62
(~11790 km2)
ERI method (depth~ 3 m)
12 ERI transects with
OhmMapper instrument
Resistivity measurement
PLANAR & DVP system
3D digital images (resolution
of 30 cm)
3D photo interpretation
(Planar-DVP)
Map drainage, cover type,
tree height, spruce-moss, slope
Establish a relation between
geophysical and photo-
interpreted variables
Extrapolate these results at
the landscape level
Planar SD Stereo/3D
EXPECTED OUTCOMES
OBJECTIVES
1.Use GPR and ERI methods to elaborate a
numerical model of the organic layer thickness at
the site level
2. Interpolate a 3D model for each study site in
order to determine the spatial variability of
organic layer thickness
3. Assess the combined effects of slope and
organic layer accumulation on forest productivity.
4. use 3D aerial photos to extrapolate these
results at the landscape level
Using very-high-resolution geophysical (GPR&ERI)
& RS 3D data
STUDY AREA
: Study site # 1Organic layer (paludified site)
Schematic of the OhmMapper instrument and
data acquisition
Inversion
process
Inverted electrical resistivity (ρ):
Low ρ ( 1 to100 Ωm = Clay-silt
ρ >100 Ωm = coarse sand &
gravel
InterpolationInterpretation
Example of 3D modelling representation of the pre-lacustrine topography of the basin of Le Lautrey,
France, in relation to the types of bedrock (Jp,J9, n2)
(Bossuet et al. 2000)
Data processing 2D cross-section.
Amato et al. 2008
Minéral
Air wave Ground wave Neige
Tourbe
Tim
e (
ns)
Dep
th(m
, v=
0.4
0m
/ns)Minéral
Air wave Ground wave Neige
Tourbe
Tim
e (
ns)
Dep
th(m
, v=
0.4
0m
/ns)
Peat
Snow
Mineral
soil
Dallaire 2007
Peatland.
Photo : D. Paré
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ERI survey divided in 12 transects
50 m
1 2 3 4 5 6
12
11
10
9 8
7
Study site
(250 x 250 m)
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ERI survey divided in 12 transects
50 m
1 2 3 4 5 6
12
11
10
9 8
7
Study site
(250 x 250 m)
Study area limitClay Belt region
APPROACH