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

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

2. 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.

3. 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

4. Prelimanary results, trial period of the IRGA NEE and Rtot for collar 6 stage recent regeneration (21 August 2003) Respiration of bare peat (5 august 2003) CO2 concentration (um/m2/s) CO2 concentration (um/m2/s)

5. For the establishment of carbon balance in Le Russey… • Dispatching of the collars : • Stage of advanced regeneration : 4 collars • Stage of recent regeneration : 4 collars • Bare 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.

6. 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.

7. For the establishment of carbon balance in Le Russey… • Leaf area index : Relation between leaf length (mm)/ leaf area (mm2) for Eriophorum angustifolium Y=0,248X1,439 R2=0,953 Relation between leaf length (mm)/dry biomass (g) for Carex nigra • Leaf biomass: Y=4e-0,6 X1,7124 R2=0,95

8. 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.

9. For the establishment of carbon balance in Le Russey… • Estimation of humidity For 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.

10. 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).

11. 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.

12. Rain collector Light sensor Air temperature sensor T. sensor T. sensor Field measurements Light sensor Chamber temperature Leaf area index Sphagnum humidity (analysis in Lab.) CO2 analyser CH4 chamber - 5 cm - 30 cm