Tree measurementsTree measurements

(Roscommon)(Roscommon)

Research objective:Research objective:

To compare modeled values of TB (using To compare modeled values of TB (using τ-ω model*) with airborne values of TB τ-ω model*) with airborne values of TB over heterogeneous tree-covered areas, over heterogeneous tree-covered areas, and by doing this, to describe the and by doing this, to describe the influence of vegetation heterogeneity on influence of vegetation heterogeneity on various model parameters by showing various model parameters by showing errors for different % cover situations.errors for different % cover situations.

* Wigneron, J.-P., J.-C. Calvet, T. Pellarin, A. Van de Griend, M. Berger, P. Ferrazzoli, Retrieving near surface soil moisture from microwave radiometric observations: current status and future plans., Remote Sens. Environ., vol

85., pp. 489-506, 2003.

Roscommon farm – tree Roscommon farm – tree areasareas

Vegetation:Vegetation:Open-forest formation: Box, Open-forest formation: Box, Ironbark & Black Cypress-Ironbark & Black Cypress-pine.pine.Open-heath understory: Sifton Open-heath understory: Sifton bushbush

Soils: sandySoils: sandy

Litter:Litter:average layer height 0.5 cmaverage layer height 0.5 cmaverage dry bulk densityaverage dry bulk density0.15 ± 0.05 g/cm30.15 ± 0.05 g/cm3

% Rock cover: high% Rock cover: high • green line = approximate sampling route for moisture measurements• black cross on line = ‘temperature measurement tree’

1. Temperature 1. Temperature measurementsmeasurements

Physical temperatures Physical temperatures necessary for modelling L-necessary for modelling L-band brightness temperaturesband brightness temperatures

Measurements (1 tree):Measurements (1 tree): Tair in canopy at 7.5m and Tair in canopy at 7.5m and

5m heights5m heights Ttree 2 cm under bark at Ttree 2 cm under bark at

1.50m height (NE & SW)1.50m height (NE & SW) Tair at ground surface (W & E)Tair at ground surface (W & E) Tsoil -2 cm (N & S)Tsoil -2 cm (N & S) Tsoil -4 cm (N & S)Tsoil -4 cm (N & S) Tsoil -50 cm (N & S)Tsoil -50 cm (N & S)

Materials: datalogger & Materials: datalogger & thermistors made by Vrije thermistors made by Vrije Universiteit AmsterdamUniversiteit Amsterdam

Results (temperatures)Results (temperatures)

Measurements of tree temperatures (NE side)

-

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

313 315 317 319 321 323 325 327

Julian day

Tem

per

atu

re (

C)

tree 7.5msurface Esoil -2cm Nbark -2cm NEsoil -50cm N

An example for measurements on the NE side of the tree during the last fortnight of NAFE.

NB. Surface values during daytime give extremely high temperatures; thermistors should have been covered to shield from direct sunlight.

2. Moisture measurements2. Moisture measurements(soil & litter)(soil & litter)

Soil & litter moisture sampled at Soil & litter moisture sampled at approx. 15 points per day, twice approx. 15 points per day, twice a week (weeks 2, 3 and 4 of a week (weeks 2, 3 and 4 of NAFE).NAFE).

Soil moisture: needed as ground Soil moisture: needed as ground truth for comparison with L-truth for comparison with L-band measurementsband measurements

Hydraprobe measurements: soil Hydraprobe measurements: soil moisture content & temperature of moisture content & temperature of top 5 cmtop 5 cm

Litter: effect of litter (moisture) Litter: effect of litter (moisture) on L-band signal is not yet on L-band signal is not yet known, some indication that known, some indication that measurements could prove measurements could prove useful for further researchuseful for further research

Same procedure used as for Same procedure used as for vegetation water content (‘grab’ & vegetation water content (‘grab’ & quadrant samples)quadrant samples)

Results (moisture)Results (moisture)15/11/05 (end of drying period)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Litter moisture (vol%)

So

il m

ois

ture

(v

ol%

)

Seems as though litter dries first, then soilSeems as though litter dries first, then soil No spatial images available yet, will later be used to compare to soil moisture No spatial images available yet, will later be used to compare to soil moisture

patterns from airborne datapatterns from airborne data

24/11/05 (after small rain)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Litter moisture (vol%)

So

il m

ois

ture

(vo

l%)

• litter dry, soil drying up • soil and litter wet after small rain but litter already starting to dry (most points < 2 vol%)

Tree photo’sTree photo’s

Fish-eye photo’s of trees taken Fish-eye photo’s of trees taken for possible further analysis & for possible further analysis & calculation of LAI (INRA calculation of LAI (INRA Bordeaux/Vrije Universiteit Bordeaux/Vrije Universiteit Amsterdam)Amsterdam)

Total of 15 photo’s taken on 7Total of 15 photo’s taken on 7thth Nov. 2005 in area around the Nov. 2005 in area around the ‘temperature measurement tree’‘temperature measurement tree’

Camera:Camera: Nikon Coolpix 4500 + Nikon Coolpix 4500 + Fish eye FC-E8Fish eye FC-E8

List of available dataList of available dataData type Measurement dates

   

T-tree 7.5m 1-24 Nov

T-tree 5m 1-24 Nov

T-bark -2cm (NE) 7-24 Nov

T-bark -2cm (SW) 7-24 Nov

T-surf (W) 1-24 Nov

T-surf (E) 7-24 Nov

T-soil -2cm (N) 1-24 Nov

T-soil -2cm (S) 1-24 Nov

T-soil -4cm (N) 1-24 Nov

T-soil -4cm (S) 1-24 Nov

T-soil -50cm (N) 10-24 Nov

T-soil -50cm (S) 10-24 Nov

   

Soil moisture (tree areas) 8, 10, 15, 17, 22, 24 Nov

Litter moisture (tree areas) 15, 17, 22, 24 Nov

   

Fish-eye photo's trees 7 Nov

Finally,Finally,

Any questions, remarks or helpful ideas:Any questions, remarks or helpful ideas:

jennifer.grant@falw.vu.nljennifer.grant@falw.vu.nl

Litter/surface SM Litter/surface SM relationshiprelationship

All days

0

5

10

15

20

25

0 20 40 60 80 100 120

litter moisture (grav%)

soil

mo

istu

re (

vol%

)

Emissivity/SM relationshipEmissivity/SM relationship

All days

R2 = 0,2837

0,88

0,89

0,9

0,91

0,92

0,93

0,94

0,95

0,96

0,97

5 10 15 20 25

soil moisture (vol%)

emis

sivi

ty

e-eff,tot

Linear (e-eff,tot)