Context, tests and considerations for field measurements (WP I) …

RECIPE

Long term objectives

• Establishment of the carbon balance in Le Russey for two different stages of vegetation :

- recent with a lot of Eriophorum angustifolium and few Sphagnum.

- advanced with mainly Sphagnum.

• Comparison with La Chaux d’Abel ( full light and biophysical variables recorded) and part of the pots of WP II)

• Compartimentation of the fluxes for a better comprehension.

For the establishment of carbon balance in Le Russey…

• Tests done this summer : Trial period for the new IRGA in order to know its

properties, the time requirred for the equilibration in the chamber and the range of possible samples :

With full light : measurement between 10 am to 3 pm. 20’ of measurement per collar :

(6’+2’) before chamber stabilization ; 6’ for the net ecosystem exchange and 6’ for total respiration ( with measurement recorded every 10’’ and averaged every minute.

12 to 14 collars

Prelimanary results, trial period of the IRGA

-10

-8

-6

-4

-2

0

2

4

160 210 260 310 360

NEE and Rtot for collar 6 stage recent regeneration (21 August 2003)

-5

-4,5

-4

-3,5

-3

-2,5

-2

-1,5

-1

-0,5

0

900 910 920 930 940 950 960

Respiration of bare peat (5 august 2003)

CO2 concentration (um/m2/s)

CO2 concentration (um/m2/s)

• Dispatching of the collars :Stage of advanced regeneration : 4 collarsStage of recent regeneration : 4 collarsBare peat : 3 collars?Rehabilitated zone : 3 collars if its seems to be OK next spring.

Choice of their positioning : for each stage of regeneration, inventory of the possible position of collars and after that random selection.

For the establishment of carbon balance in Le Russey…

For the establishment of carbon balance in Le Russey…

• Leaf area index : indirect measurement based on calibration :

relation between leaf length and area. Scan of 75 leaves per species :

Eriophorum angustifolium

Eriophorum vaginatum

Carex nigra.

For Vaccinium oxycoccos, leaves scanned, recording of number of leaves in various size classes.

For Sphagnum and Polytrichum, measurement of density and estimation of the photosynthesis height with a light sensor.

For the establishment of carbon balance in Le Russey…

0

500

1000

1500

2000

2500

3000

0 100 200 300 400 500 600

Relation between leaf length (mm)/ leaf area (mm2) for Eriophorum angustifolium

Y=0,248X1,439

R2=0,953

0

0,01

0,02

0,03

0,04

0,05

0,06

0,07

0,08

0,09

0,1

0 50 100 150 200 250 300 350 400

Relation between leaf length (mm)/dry biomass (g) for Carex nigra

Y=4e-0,6 X1,7124

R2=0,95

•Leaf area index :

•Leaf biomass:

For the establishment of carbon balance in Le Russey…

• Biophysical variables :

Installation of the rain collector, light sensor, air and deep peat temperature sensor at the site. For the peat temperature at 5 and 30cm depth at each stage.

Hobo sensors, measurements every 30’ with a large autonomy.

For the establishment of carbon balance in Le Russey…

• Estimation of humidityFor the peat, test with a thetaprob sensor : the

integration of the conductivity for a height of 6cm is too approximative for this kind of soil

For the Sphagnum, test of the visual index already used :1 (Sphagnum completely dessicated) 2 (Sphagnum 1cm = capitulum dessicated)3 (Sphagnum just rehydrated)4 (Sphagnum good humidified)5 (Sphagnum gorged with water).

In order to test it : sampling of 20 plants of 4cm and weight fresh and dry biomass. The difference between the index was statistically significant.

For the establishment of carbon balance in Le Russey…

• Measurement campaign:

Once a week (except with snow) for CO2

Every two or three weeks for CH4 (incubation in a small chamber placed near each collar and analysis in the laboratory with the micro GC).

For La Chaux d’Abel…

• Utilisation of the tests done in Le Russey. • Installation of sensors in order to record

biophysical variables.• Measurement once a month for 12 collars with

full light.

Field measurements

Light sensor

Rain collector

Air temperature sensor

CH4 chamber

T. sensor

T. sensor

- 5 cm

- 30 cm

Chamber temperature

CO2

analyser(analysis in Lab.)

Light sensor

Leaf area index

Sphagnum humidity