Tremellomycetes. Tremellales. â Fungal diversity increase with decomposition time â later Basidiomycota. â Rain deficit affect the relative abundance of ...
Rainwater deficit affects litter mass loss and microbial decomposer communities in a Mediterranean forest K. Diallo, M. Santonja, S. Pereira, V. Baldy, T. Gauquelin, C. Fernandez, P. Mirleau
Sfécologie2016 25/10/2016
Previsional climate change globally
Comparing 1960–1989 records to 2060-2089 estimates Podale et al. (2014) The key role of dry days in changing regional climate and precipitation regimes. Scientific Reports.
! Increasing frequency of dry days in several temperate regions Sfécologie2016 25/10/2016
Previsional climate change in the Mediterranean
Heavy precipitation (%)
December - February:
ì
Number of heat waves
Lenght of dry spells (days)
May - September:
June – August:
ì
yearly:
ì
î
Comparing 1971–2000 records to 2071-2100 estimates IPCC (2014) Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part B:Regional Aspects. Sfécologie2016 25/10/2016
What effects on forest ecosystems functionning ?
Reduced water ressource Stress
² Reduction of plant biomass production? ² Shift from primary to secondary metabolism? ² Change of leaf litter chemistry?
Stress
Feedback stress
² Change in decomposer community? ² Reduction of the mineralisation process? Decrease nutrient availability
ANR Project SEC-PRIME2 (2012-16) Trade-off between SECondary and PRImary MEtabolism in MEditerranean forest under climate change. Sfécologie2016 25/10/2016
O3HP : experimenting reduced precipitation on the functioning of forest ecosystems Marseille !
" O3HP
Treatment à sliding shutters excluding about 30% rain based on average rainfall in the past decade
Two levels scaffolding à access to the soil and to the canopy Sfécologie2016 25/10/2016
O3HP : experimenting reduced precipitation on leaf litter decomposition ² Incubation of litterbags under contol (C) and rain exclusion (RE) conditions Meteorology data
15 possible litter mixtures containing 1, 2, 3 or 4 leaf species of: Quercus pubescens Acer monspessulanum Cotinus coggygria
Sample collection and labwork: ² Litter mass loss ² Litter chemistry ² Mesofauna ² DNA extraction àMicrobial abundances (qPCR) àMicrobial diversity (Illumina Miseq)
Pinus halepensis Sfécologie2016 25/10/2016
O3HP : the rain exclusion treatment during litterbags incubation ² Meteorology helped choosing appropriate sampling dates!
800
120
Air temperature (°C)
100 80
1000
2012: Cumulative precipitations Δ precipitation = 273.8 mm
800
600
600
400
400
200
200
0
0
2013: Cumulative precipitations Δ precipitation = 299.9 mm
240 200 160
60
120
40
80
20
Precipitations (mm)
1000
40
0
0 J
F
M
A
M
J
J
A
S
O
N
D
J
F
M
A
2012 air temperature
M
J
J
A
S
O
N
D
2013 precipitation "control plot"
J
F
M
2014
precipitation "drought plot"
Litterbags were collected following periods of maximum rain exclusion (30%) Sfécologie2016 25/10/2016
Method to decipher leaf litter microbial diversity The metabarcoding experiment Fungal ITS1 18S tag
Pr F
28S
5S
ITS1 fung
Pr R
tag
PCR
Bacterial 16S v3-v4 23S
16S tag
Pr F
16S v3-‐v4 bac
Pr R
Sequencing Illumina paire-end (2x300)
tag
FastQ files
Mothur pipeline
OTU abundance matrix OTU Taxonomy matrix Sfécologie2016 25/10/2016
Results: litter mass loss
Li@er mass loss (g)
8 months
20 months
10
10
9
9
8
8
7
7
6
*
5
**
*
3
3
2
2
1
1
0
0
3
4
***
**
*
2
3
4
5 4
2
Rain exclusion
6
4
1
Control
1
Li@er richness
àLitter decomposition is not affected by leaf litter richness ! Rain deficit lowers leaf litter decomposition
Sfécologie2016 25/10/2016
Fungal abundance
Log (ITS copy number . g-‐1
Bacterial abundance
Log (16S rDNA copy number . g-‐1
Results: bacterial and fungal abundances 8 months
12
20 months Control
10
Rain exclusion
8 6 4 2 0 12 10 8 6 4 2 0 1
2
3
4
1
Li@er richness
2
3
4
à Microbial abundance increase with decomposition time à Variation of microbial abundance with litter richness interacts with time à Rain deficit doesn’t affect microbial abundance ! Sfécologie2016 25/10/2016
à Bacterial diversity increase with decomposition time à Rain deficit affect the relative abundance of Actinobacteria to the profit of Proteobacteria, Acidobacteria and bacteroidetes Sfécologie2016 25/10/2016
à Fungal diversity increase with decomposition time – later Basidiomycota à Rain deficit affect the relative abundance of Schizoparmaceae to the profit of Gnomoniaceae Sfécologie2016 25/10/2016
To conclude 4 Control Exclusion Decomposition
PC2 (16.6 %)
2
S actinobacteria [Fungi] [Bacteria] S Bacteroidetes S proteobacteria
0
S acidobacteria
-2 S gnomoniaceae
-4 -6
-4
-2
0
PC1 (33.9 %)
2
4
6
Rain deficit affects litter decomposition and associated microbial diversity. What about microbial functions of particular importance for nutrient cycling? à Biocomputing package Tax4fun may provide some clues…
