Using Ground Penetrating Radar in Agroforestry Systems: Quantification of Tree Root Distribution and BiomassKira A. Borden & Dr. Marney E. IsaacUniversity of Toronto, Canada
New tools and paradigms
Managed multispecies ecosystems
• Interspecific variation
• Intraspecific plasticity
• Community-level processes
?Photo credits: M. Isaac
The hidden half of trees
• 20 to 40% of tree biomass located belowground (Brunner and Godbold 2007)
• Trade-offs relating to nutrient acquisition between competition and improved cycling
• Research limited by methodological constraints
Photo credit: M. Isaac
Non-intrusive belowground study
k = dielectric constant of a medium
Figure from Isaac & Anglaaere, 2013, Ecology and Evolution
Coarse root detections
0.5 m 0.5 m
Photo credits: K. Borden
0.7 m
ObjectivesBiomass estimation
Distribution detection
Photo credit: K. Borden Photo credit: M. Isaac
C storageNutrient acquisition
Tree-based intercropping Canada
Cocoa-shade Ghana
xy
Photo credits: K. Borden
x
y
Thuja occidentalis
Radar signal reflections
82.2g
5.1g
355.7 cm2
66.9 cm2
Biomass estimation
Borden et al. under review
Photo credit: K. Borden
Photo credit: K. Borden
P = 0.0003
Borden et al. under review
Biomass estimation
54.1 ± 8.7 kg tree-1
(n=12)
54.8 ± 8.3 kg tree-1
(n=12)
Distribution detection
Reflection points of detected spruce tree roots
0 1 2 3 4 5
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0
1
2
3
4
5
X (m)
Y (
m)
Depth
(m
)D
epth
(cm
) 10
20
30
40
50
60
700 1 2 3 4
43
21 y (m)
Figure from Isaac & Anglaaere, 2013, Ecology and Evolution
x (m)
Interspecific root plasticity
Borden et al. in preparation
Picea abies
n = 2
Juglans nigra
n = 3
• Coarse root depth data show distinct rooting patterns across five tree species
• Deep-rooted tree species below crop rooting zone
Intraspecific root plasticity
Isaac et al. 2014, Agriculture, Ecosystems and Environment
(n = 12)
Importance to agroforestryBiomass estimation
Distribution detectionC storageNutrient acquisition
C storage - species-specific root C
concentrations
Acquisition zones - δ18O isotopic signature
matching
Site-level C storage in coarse roots: 2.3 Mg C ha-1 (Borden et al. under review)
Larger zone of acquisition for cocoa with shade tree under sandy loam soils (Isaac et al. 2014)
Thank youWorld Congress on Agroforestry - conference organizers
Forestry Research Institute of Ghana (Dr. Luke Anglaaere, Dr. Stephen Adu-Bredu)
The Faculty of Forestry, University of Toronto (Dr. Sean Thomas)
The University of Guelph, Canada (Dr. Naresh Thevathasan, Dr. Andrew Gordon, Amy Wotherspoon)
Agriculture and Agri-Food Canada
Natural Sciences and Engineering Research Council of Canada
Photo credit: K. Borden
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