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

In March, N and H2O- increased CH4 uptake

production

uptake

H2O- increased CH4 uptake

production

uptake

N increased CH4 uptake

production

uptake

Rain decreased, then increased uptakeproduction

uptake

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

H2O- decreased respiration

Time interacts with precipitation

Time interacts with precipitation

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

N increases N2O release

Time interacts with N treatment

Time interacts with N treatment

Rain Effect?

Drought changed bacterial community

Ambient Rainfall Reduced Rainfall

Significantly Different Phyla

Reduced rainfall decreases variability in microbial richness at OTU level

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

Questions?Questions?