Heat Ratio Method Sap Flow - ICT International

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Heat Ratio Method

&

Sap Flow

ICT International

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Definitions

– Stem diameter = stem width

– Xylem = sapwood + heartwood

– Sapwood = conducting tissue

– Heartwood = non-conducting

tissue

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Definitions

Positive Flow

Zero Flow

Reverse Flow

Radial Profile

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A Brief History of HRM…

– 1998 to 2000, limitations with

existing methods

– Low and reverse flow

– Dr Stephen Burgess,

University of Western Australia

– Seminal publication:

Burgess et al. (2001) Tree Physiology 21: 589-598.

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A Brief History of HRM…

Burgess et al. (2000) Annals of Botany 85: 215-224

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A Brief History of HRM…

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Thermistor Location

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a c

Temperature sensors

Downstream temperature probe

Upstream temperature

probe

Heater probe x

x

Bark + cambium

Sapwood Heartwood Centre of stem

Sapflow

db

Needles Installed in a Tree

Outer Inner

(a,b) (c,d)

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Step 1: Initial Temperature – 31 sec

a c

Temperature sensors

Downstream temperature probe

Upstream temperature

probe

Heater probe x

x

Bark + cambium

Sapwood Heartwood Centre of stem

Sapflow

db

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Step 2: Heater Pulse – 2.68 sec

a c

Temperature sensors

Downstream temperature probe

Upstream temperature

probe

Heater probe x

x

Bark + cambium

Sapwood Heartwood Centre of stem

Sapflow

db

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Step 3: Wait – 60 sec

a c

Temperature sensors

Downstream temperature probe

Upstream temperature

probe

Heater probe x

x

Bark + cambium

Sapwood Heartwood Centre of stem

Sapflow

db

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Step 4: Measure Temp – 40 sec

a c

Temperature sensors

Downstream temperature probe

Upstream temperature

probe

Heater probe x

x

Bark + cambium

Sapwood Heartwood Centre of stem

Sapflow

db

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Raw Temperature Mode – Outer Sensor Tem

pe

ratu

re (

C)

Time (seconds)

0 20 40 60 80 100 120 140

32.4

32.6

32.8

33.0

33.2

33.4

Downstream

Upstream

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Time (seconds)

0 20 40 60 80 100 120 140

32.4

32.6

32.8

33.0

33.2

33.4

Step 1: Initial Temperature Tem

pe

ratu

re (

C)

31 seconds initial temperature

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Time (seconds)

0 20 40 60 80 100 120 140

32.4

32.6

32.8

33.0

33.2

33.4

Step 2: Heat Pulse Tem

pe

ratu

re (

C) 2.68 seconds

heater pulse

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Time (seconds)

0 20 40 60 80 100 120 140

32.4

32.6

32.8

33.0

33.2

33.4

Step 3: 60 second wait Tem

pe

ratu

re (

C)

60 second wait

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Time (seconds)

0 20 40 60 80 100 120 140

32.4

32.6

32.8

33.0

33.2

33.4

Step 4: Temperature Measurement Tem

pe

ratu

re (

C)

40 second measurement period

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vh = heat velocity k = thermal diffusivity v1 = average increase temperature downstream v2 = average increase temperature upstream x = distance of temperature needles from heater needle 3600 = converting from seconds to hours

Raw Heat Velocity Equation

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Time (seconds)

0 20 40 60 80 100 120 140

32.4

32.6

32.8

33.0

33.2

33.4

Calculating v1 and v2Tem

pe

ratu

re (

C) v1 = 0.538 C

v2 = 0.294 C

on oil, & en

Calculating v1 and v2

Time (seconds)

20 40 60 80 100 120 140 160

v1/v

2

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Heat Pulse

Calculating v1 and v2

Time (seconds)

20 40 60 80 100 120 140 160

v1/v

2

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Only use the last 40 seconds of data

Calculating v1 and v2

Time (seconds)

20 40 60 80 100 120 140 160

v1/v

2

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Linear Equation for last 40 seconds of data:

y = 0.0004x + 1.82

Note slope is less than 0.01

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Raw Heat Velocity Equation

k = 0.0025 cm2 s-1

x = 0.5 cm v1 = 0.538 C v2 = 0.294

C

vh = 10.865 cm hr-1

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ZERO Flow:

k = 0.0025 cm2 s-1

x = 0.5 cm v1 = 1.0 C v2 = 1.0

C

vh = 0.000 cm hr-1

vh =

Raw Heat Velocity Equation – Zero Flow

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REVERSE Flow:

k = 0.0025 cm2 s-1

x = 0.5 cm v1 = 0.7 C v2 = 0.9

C

vh = -4.523 cm hr-1

vh =

Raw Heat Velocity Equation – Reverse Flow

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LOW Flow:

k = 0.0025 cm2 s-1

x = 0.5 cm v1 = 0.71 C v2 = 0.70

C

vh = 0.255 cm hr-1

vh =

The logarithm of v1/v2 allows for low flow

Raw Heat Velocity Equation – Low Flow

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vh = heat velocity k = thermal diffusivity v1 = average increase temperature downstream v2 = average increase temperature upstream x = distance of temperature needles from heater needle 3600 = converting from seconds to hours

Raw Heat Velocity & Thermal Diffusivity

Thermal Diffusivity

Definition:

The thermal conductivity of a substance divided by the product of its density and its

specific heat capacity.

Marshall (1958): k = 0.0025 cm2 s-1

Values range between 0.0014 (water) and

0.004 (dry wood)

Measure directly with Decagon’s KD2 Pro:

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Thermal Diffusivity – Empirical Technique

Equation 8:

k = thermal diffusivity Kgw = thermal conductivity p = basic density of wood (dry weight/fresh volume) c = specific heat capacity of fresh wood matrix

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Thermal Diffusivity – Empirical Technique

Equation 9:

Ks = thermal conductivity of water (5.984 x 10-1 J m-1 s-1 at 20 C) Kw = thermal conductivity of dry wood matrix (see next slide) pb = basic density of wood (dry weight/fresh volume) cw = specific heat capacity of wood matrix cs = specific heat capacity of sap mc = water content of sapwood ps = density of water

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cw = 1200 J kg-1 C-1 at 20 C cs = 4182 J kg-1

C-1 at 20

C

ps = 998.2071 kg m-3 at 20 C

Equation 9:

Thermal Diffusivity – Empirical Technique

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pb = basic density of wood (dry weight/fresh volume)

mc = water content of sapwood

Thermal Diffusivity – Empirical Technique

Equation 9:

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– Collect sapwood sample

– Fresh weight as soon as possible

– Volume: cylinder or Archimedesprinciple

– Dry weight: 2 days in oven at 60°C

Fresh & Dry Weight, and Fresh Volume

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Thermal Diffusivity – Empirical Technique

Equation 10:

Equation 11:

Equation 9:

Fv = void fraction

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Thermal Diffusivity – Empirical Technique

Equation 12:

wf = fresh weight (kg) wd = oven dried weight (kg)

Equation 8:

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Converting Raw Data to Sap Flow

Heat Velocity

Wound Response & Wood Properties: Fresh and dry weight, fresh volume

Sap Velocity

Stem Properties: Bark, sapwood, heartwood, diameter

Sap Flow

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Wound Response

Wound Response

Table 1:

Equation 6:

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Calculating Sap Velocity

Equation 7:

Vs = sap velocity Vc = heat velocity corrected for wound diameter pb = basic density of wood (dry weight/fresh volume) cw = specific heat capacity of wood matrix cs = specific heat capacity of sap mc = water content of sapwood ps = density of water

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Calculating Sap Velocity

Equation 7:

cw = 1200 J kg-1 C-1 at 20 C cs = 4182 J kg-1

C-1 at 20

C

ps = 998.2071 kg m-3 at 20 C

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Calculating Sap Velocity

Equation 7:

pb = basic density of wood (dry weight/fresh volume)

mc = water content of sapwood

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Calculating Sap Velocity

– Collect sapwood sample

– Fresh weight as soon as possible

– Volume: cylinder or Archimedesprinciple

– Dry weight: 2 days in oven at 60°C

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The Heat Ratio Method

Heat Velocity

Wound Effect, Thermal Diffusivity & Wood Properties: Fresh and dry weight, fresh volume

Sap Velocity

Stem Properties: Bark, sapwood, heartwood, diameter

Sap Flow

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Calculating Sap Flow

Sapwood

Heartwood

Bark

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Stem Properties

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Total Tree Sap Volume

A1

A2

Heartwood Sapwood

A1 = Sapwood Annulus 1

A1 = Outer Sensor

A2 = Sapwood Annulus 2

A2 = Inner Sensor

Sap flow Sensor

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Total Tree Sap Volume

A1 = 2.4 units

A2 = 1.1 unit

Sap Volume = 3.5 units

A1

A2

HeartwoodSapwood

Sap flow Sensor

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The Radial Profile

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40 50 60

Sap

Velo

cit

y(c

mh

r-1)

Radial Distance from Outside of Stem (mm)

Note: demonstration data only

Bark Heartwood

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The Radial Profile – Heat Ratio

Method

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40 50 60

Sap

Velo

cit

y(c

mh

r-1)

Radial Distance from Outside of Stem (mm)

Note: demonstration data only

Bark Heartwood

Outer Sensor

Inner Sensor

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Total Tree Sap Volume – Large Sapwood

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0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40 50 60

Sap

Velo

cit

y (

cm

hr-

1) Outer Sensor

Inner Sensor

X

X

Large Sapwood – Linear Decrease

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0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40 50 60

Sap

Velo

cit

y (

cm

hr-

1) Outer Sensor

Inner Sensor

X X

Large Sapwood – Hold Value

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Tree Water Use Californian Redwood, over 100m tall

Approx. 2000 litres per day

Coolibah, 18m tall Approx. 260 litres per day

Wattle, 4m tall Approx. 15 litres per day

Eucalypt Sapling, 1.5m tall Approx. 0.2 litres per day

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ICT International Pty Ltd Solutions for soil, plant and environmental monitoring

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Sales@international.com

Phone: 61 2 6772 6770

Fax: 61 2 6772 7616

PO Box 503, Armidale, NSW, Australia, 2350 INTERNATIONAL

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