RECIPE - Munchen May 2005

ECOBIO

ECOBIO

UMR 6553

Influence of vegetation cover and age of regeneration stages on C and N soluble and microbial variables

K-W test

Anaerobic activity

0

1

2

3

4

5

6

7

8

< 5 5 to 10 10 25 > 50

Age of regeneration stage

C re

leas

e (µ

g C

g D

P-1

H-1

)

P-Values SOC SON SOC/SON

Country < 0.001 < 0.001 < 0.001

Depth 0.018 0.054 0.543

Vegetal Cover 0.059 < 0.0001 < 0.0001

Age 0.0004 0.005 0.0011

Soluble Organic Nitrogen

0

100

200

300

400

Bare

P

Care

x Ea EvD

EvW

SEEC

Spse Sf

Sf Ea

Sf Ev

SpMo

Vegetation Cover

N (

ppm

DP)

Quantifying and fitting kinetics of C mineralization

CO2 FI E en aérobie

0

2000

4000

6000

8000

10000

0 1 2 3 4 5 6 7

Temps en jour

CO

2 en

ppm

Example : Aitoneva - bare peat

CO2 FI A en aérobie

0

2000

4000

6000

8000

10000

0 1 2 3 4 5 6 7

Temps en jour

CO

2 en

ppm

Eriophorum vaginatum wet

model with 2 boxes to data on cumulative release over time :

C-CO2 release = Cm. (1-e-Kmt) + .tWhere - C-CO2 = the cumulative C released to time t (days), - Cm = potentially mineralizable C corresponding to the stock of SOC (µg g-1 DP),- K (d-1) = instantaneous release rate of this nutrient pool,- whereas the C recalcitrant pool mineralization rate would be associated to (mg C g-1dry peat d-1).

Methane kinetics modelling

From the different results : 2 types of curves

Potential C-CH4 emission Scotland B3 Aerobiosis

y = 49,47x2 - 187,09x + 147,02

R2 = 0,998

0200400600800

100012001400

0 1 2 3 4 5 6 7 8Days

C-CH

4 (n

g g

DP-1

)

Potential C-CH4 emission Finland E4 Aerobiosis

y = -14,20x2 + 109,82x - 77,49

R2 = 0,887

0

100

200

300

0 1 2 3 4 5 6 7 8

DaysC

-CH

4 (n

gC

g D

P-1

)

PCA of microbial variables (WP 1)

0.0

0.0

0.2

- 0.1 0.2

0.4

- 0.4

0.6

0.4

Fungal Activity

Bulk Density

Bacterial Activity

Aerobic/Anaerobic Activity

C mineralization rate (Anaerobic)

Microbial N Microbial C

C mineralization rate (Aerobic)

Microbial Biomass (SIR)

Microbial Activity (Anaerobic)

Microbial Activity (Aerobic)

Component 1

Component 2

Component number

Eigenvalue Percent of Variance

Cumulative %

1 3.011 27.4 27.4 2 2.451 22.3 49.7 3 1.848 16.8 66.5 4 1.193 10.8 77.3

Plot of component weight

PCA - WP1

- 2.0

- 4.0

0.0

2.0

4.0

Component 2

- 2.0 - 3.0 0.0 4.0 - 1.0 3.0 1.0 2.0

Component 1

Empty circle = Scotland ; Full circle = Baupte Empty triangle = Le RusseyFull triangle = Chaux d’Abel ; Diamond = Finland

Scatterplot

Fate of litter Installing jars with peat columns

Lids to close the jars for measuring gaz emission

Fate of C and N in the peat column

Stocks and fluxeswhich are analyzed

Labelled litter

13C - 15N

15N mineralization

towards microbes

Microbial communities : 13C PLFA analysis 13C & 15N in microbial biomass

towards peat

13C & 15N (K2SO4 extract without fumigation)

Peat column

E. angustifolium at the experiment start

Fate of litter N

Conditions of incubation :16/8 hours day/night

photoperiod80 % humidity air saturationAir temperature :

18°C day, 10 °C night

PVC tube in a jar with peat from Le Russey

Litter adjusted at the surface of the peat column inside the PVC tube (see black arrow)

fiber glass nets : see upper

Water-level in the jar

10 cm height

fiber glass net

Cap of the jar with a septum in the middle

6.5 cm diameter

C-CO2 kinetics

The priming effect

C-CO2 emission in the jars

0

2

4

6

8

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Days

µgC

gD

P-1

H-1

E. Angustifolium

E . Vaginatum

Sphagnum

Bare peat

Gas Chromatograph

GC Analysis of C (CO2-CH4) release in closed jarsAnalysis of total C and N in water(losses from the peat column ??)

15N methodology and calculation

• Calculation of the N recovery• For each selected compartment (peat, N mineral,

microbial biomass, etc.), the recovery from the N input is calculated as :

% R = (Ei/Eo) * (Ni/a) * 100

With :

• Ni = N stock of the compartment i

• a = N mass of the input (litter at the start of the experiment)

• Ei = isotopic excess of the compartment i

• Eo = isotopic excess of the input

• Ei/Eo corresponds to the N part coming from the tracer. This is equal to the Ndff = Nitrogen derived from fertilizer (Powlson & Barraclough 1993, Guiraud & Boniface 1987)

Fate of litter NSphagnum fallax

Sphagnum fallax 100.00 78.84

1.55 0.00

62.58

25.75

4.18 0

10 20 30 40 50 60 70 80 90

100

Date 0 Date 1 Date 1 Date 1 Date 2 Date 2 Date 2

Litter Litter Surface peat

deep peat

Litter Surface peat

deep peat

Recovery (%)

Fate of N from the litter

Eriophorum angustifolium litter

Eriophorum angustifolium

100.00

75.80

4.74 0.16

66.68

15.59 0.64

0 20 40 60 80

100

Date 0 Date 1 Date 1 Date 1 Date 2 Date 2 Date 2

Litter Litter Surface peat

deep peat

Litter Surface peat

deep peat

Recovery (%)

Fate of N from the litter

Concluding remarks

• Fate of N from liter : as the N decreases from litter, it increases in the peat but in which

compartments :- probably microbial biomass- mineral N ??

• Signicant decay through time (2 months) mineralization takes place at this time level

(shown by the decreasing of N mass in the litter, not presented here)

Fate of litter : what about C ?

13 C in from the harvesting of gaz emissions : OK13 C in the litter and the peat : OK

but I need the value of natural abundance value to calculate the recovery in litter through time)

In addition, we ‘ve got samples at 6 months …