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Impact of varied precipitation and N deposition on grassland soil
microbial communities and GHG flux
Emma L. AronsonAllison labUC Irvine
May 17, 2012
Precipitation hypotheses
Indicates level of soil bacterial biodiversity
Decreased Rainfall Control Increased Rainfall
Indicates rate of CO2 and N2O release, CH4 consumption
N amendment hypotheses
Control
Indicates level of soil bacterial biodiversity
Indicates rate of CO2 and N2O release, CH4 consumption
N Added
N N N N N N
CH4 flux correlates with initial [CH4]
500 1000 1500 2000 2500 3000 3500
80
60
40
20
0
-20
-40
-60
-80
CH
4 F
lux
(ppb
min
-1)
production
uptake
Rainfall increases respiration
Courtesy of Greg Winston
CO2 F
lux
(mg
m-2
h-1
) Precipitation (in d-1)
Day of Study
Precipitation
CO2 Flux
Drought decreased respiration and variability in bacterial diversity, increased CH4 uptake
Decreased Rainfall Control Increased Rainfall
Indicates rate of CO2 release, CH4 consumption
microbial community variability
N amendment increased N2O release, CH4 uptake
N Added Control
N N N N N N
Indicates rate of N2O release, CH4 consumption
Research in progress
• Further 16S 454 sequencing – for all dates of gas analysis
• Shotgun metagenomic DNA sequencing • GeoChip functional microarrays or qPCR• Gene expression of soil N and C cycling
functions