Transcript Estelle Bortoluzzi

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
4
NEE and Rtot for collar 6 stage recent
regeneration (21 August 2003)
2
0
-2
160
210
260
310
360
-4
-6
-8
-10 concentration (um/m2/s)
CO
2
Respiration of bare peat (5 august 2003)
0
-0,5900
910
-1
-1,5
-2
-2,5
-3
-3,5
-4
-4,5
-5
CO2 concentration
(um/m2/s)
920
930
940
950
960
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.
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…
•Leaf area index :
Relation between leaf length (mm)/ leaf area (mm2)
for
3000Eriophorum angustifolium
Y=0,248X1,439
2500
R2=0,953
2000
1500
1000
0,1
500
Relation between leaf length (mm)/dry
biomass (g) for Carex nigra
0,09
0,08
0
0
100
200
300
400
500
0,07
600
0,06
0,05
0,04
•Leaf biomass:
0,03
Y=4e-0,6 X1,7124
R2=0,95
0,02
0,01
0
0
50
100
150
200
250
300
350
400
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 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.
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
Light
sensor
Air temperature sensor
Leaf area index
Sphagnum humidity
(analysis in Lab.)
CH4 chamber
- 5 cm
T. sensor
- 30 cm
T. sensor
Chamber
temperature
CO2
analyser