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