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Biodiversity and rhizosphere process in plant/soil synchronization
Camille Cros, Gaël Alvarez, Frida Keuper, Sandrine Revaillot, Sébastien Fontaine
To cite this version:
Camille Cros, Gaël Alvarez, Frida Keuper, Sandrine Revaillot, Sébastien Fontaine. Biodiversity and rhizosphere process in plant/soil synchronization. Meeting BASIL, Apr 2016, Lleida, Spain. �hal- 02793854�
Biodiversity and
rhizosphere process in
plant/soil synchronization
Lleida April 2016
1
BASIL: Biodiversity and ecosystem services
Introduction
•
Factors controlling plants growth and microorganisms activities are different
Few probability to observe a synchronization between them
Soil offer Plant demand
SOM N mineral
mineralization
N mineral Biomass
T°C
Moisture
texture Microbes
communauties
SOM properties
photosynthesis
T°C Light Vegetal
communauties
Health
Management
2
In grassland
•
Few leaching
N uptake by plant
Grassland is a quite autonomous agroecosystem
Recous et al., 1997
% N supply
years N leaching
P
Annual crop
Grassland presence
Bare soil
c
Presence of synchronization between plant N-demand and soil N-offer ?
3
Rhizosphere regulation intensity change according to N and C availability
N mineral
SOM
Soil organic matter
FOM
Fresh organic matter Easily available substance
N uptake
Humification
« Mining »
soil
SOM builders
SOM decomposers Microbial biomass
In grassland
Fontaine et al., 2011 Perveen et al., 2014
•
Plants control this synchronization according to their own need (model):
bank mechanism
4
In grassland: Questions
Do we observe a synchronization between plant demand and soil offer with a grass species ?
How evolve rhizosphere process with a legume intercrop (N treatment)?
How evolve rhizosphere process and ecosystem balance in a elevated CO2 environment in grassland
(grass alone and intercrop) ?
5In conventional crop
•
High leaching
N lost in environment
dependent to fertilizer
soil exhaustion
Recous et al., 1997
Annual cropping
6
In conventional crop: Question
Do we observe a synchronization in conventional annual crop ?
We hypothesize no due to absence of perennial species
7
In agro-ecological design
•
Increasing use of fertilizer , no longer followed by a matching increase in crop-production
Yield (x2) N (x7)
Nitrogen fertilizer
Tilman et al., 2002
8
In agro-ecological design
•
Stagnation of production after 2000
N (x7)
Nitrogen fertilizer
9
Wheat Yield in France
t/ha
In agro-ecological design
•
Conventional crop: source of high environmental impact
Steffen et al., 2015
10
In agro-ecological design
•
We want to use the presence of synchronization in natural ecosystem (ie: grassland) to restore it in crop production
•
To observe that we set up wheat / grassland intercrop
Could we observe a synchronization between N demand and soil offer in innovative agroecosystem?
How evolve rhizosphere process according to N fertilizer intensity ?
Importance to find another way of production
11
Transversal question
Understand: how occur plant/soil synchronization according to season?
Difference in plant and microbes activities through seasons (Bardgett et al., 2005)
We hypothesize rhizosphere process are different according to season:
storage during automn/winter and release during spring/ summer
We suppose the importance of perennial species in this plant/soil synchronization
12
To answer those questions
….
13
10 plants treatments with 4 repetitions :
•
3 species
Wheat White clover
English Ryegrass
+ Manipulation of Nitrogen and Carbon availability
14
Questions related to synchronization in grassland ecosystem
Bare soil grass
monocrop Grassland (Intercrop with white clover)
Ambient CO2
Ambient CO2
Elevated CO2
Elevated CO2
N- N- N- N-
5 treatments
15
Questions related to land use: How evolve synchronization according to management intensity ?
6 treatments
monocrop Intercrop with grassland Wheat
N+ N- N+ N-
Grassland
N+ N-
Management intensity 16
Experimental devices
17
Labeling plateform (13CO2) and gas exchanges measurments
18 Input
sample
output sample
electrovalves
Innovative design with 13C continuous labeling for 2 years
19
Labeling plateform (13CO2) and
gas exchanges measurments
5 octopus
8 chambers by octopus 40 chambers Elevated CO2
20
Labeling plateform (13CO2) and
gas exchanges measurments
The chambers
Day chamber Belowground Night chamber chamber
21
Belowground chamber
• Leaching collection
10 cm Water tank 90 cm Soil column
Water tank Pipe to collect leaching
22
The chambers
Belowground chamber
• Buried at 80 cm
• Check chambers are flat in soil
23
The chambers
1 input
2 outputs
• Continuous measures of C fluxes at entry and exit
Day chamber
24
The chambers
Day chamber
We can disconnect day chambers from air distribution system
25
The chambers
Night chamber
• Measure respiration of microbes/plant system
Permit to determine RPE
TOP
Syringe to keep air
26
The chambers
27
Measured ecosystem functions
Continuously:
Net ecosystem exchange
Ecosystem respiration
Plant photosynthesis (GPP)
Bi-monthly:
Plant (labeled) C respiration
Soil (unlabeled) C respiration
Rhizosphere priming effect
Emissions of N20
Emission or fixation of methane
Seasonally
Leaching
Forage production and grain yield
Destructive measurements
2 greenhouses without continuous labeling
Elevated CO2
28
Estimate microbial activity and soil N process according to seasons
Measurement at each sampling (one per season):
•
Sampling soil to evaluate:
• Microbial biomass
• gross N mineralization and immobilization
• Microbial communities: DNA, PLFA ?
•
15N input to follow N distribution into
plant/soil system
29Destructive measurements
Greenhouse 1 at ambient CO2
•
8 treatments
•
4 repetitions
•
3 harvest corresponding to 3 seasons
96 pots
30
Destructive measurements
Greenhouse 2 at elevated CO2
•
2 treatments
•
4 repetitions
•
3 harvest corresponding to 3 seasons
24 pots
31
Destructive measurements
The pots
10 cm Water tank 90 cm Soil column
Water tank
Unscrew bottom to sample leaching
32
Destructive measurements
Soil
•
From grassland on 0-90 cm
•
3 layers separated : 5-20, 20-50, 50-90 cm
•
Each layer sieved at 1 cm
90 cm
5 cm
Remove due to high root density
33
Soil in pots
reserve
3 cm 10 cm
42 cm 30 cm 15 cm
sand Layer 3
Layer 2 Layer 1
34
THANKS FOR
YOUR ATTENTION
35
Introduction
•
In grassland, no or few leaching
•
In conventional crop, high leaching
Recous et al., 1997
% N supply
years N leaching
P
Annual cropping Rotation annual
cropping and grassland
Grassland presence
Bare soil
36
Common questions
Understand how occur this synchronization according to C and N availability ?
According to Perveen et al (2014) and Fontaine and Barot ( 2006), presence of differences according to nutrients availability
Understand how occur plant/soil synchronization according to season?
Difference in plant and microbes activities through seasons (Bardgett et al., 2005)
37
Set up: space station
1 input
2 outputs
Continuous measure of C fluxes , GES
Day chamber
measuring point
382 types of set up
Set up to characterize
ecosystem C and N cycling
39
