Talk presented at Ecological Society of America meeting in Sacramento, CA - August 2014.

1. Soil bacterial community structure remains stable with
rising temperature in Hawaiian montane wet forests
Paul C. Selmants, Karen L. Adair, Creighton M. Litton,
Christian P. Giardina & Egbert Schwartz

2. Bacteria are the most abundant
and diverse organisms on Earth

3. How will soil bacteria respond
to climate warming?

4. How will soil bacteria respond
to climate warming?
Climatic controls on bacterial
distribution poorly resolved

5. How will soil bacteria respond
to climate warming?
Climatic controls on bacterial
distribution poorly resolved
Shift in diversity could alter
biogeochemical cycling

6. Hawaii Mean Annual Temperature Gradient
800-1600 m (13-18.2 °C)
A model study system:
- Constant plant spp. composition
- Constant disturbance histories
- Constant substrate age & type
- Constant soil water balance
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18.2 °C
17.3 °C
16.7 °C
16.1 °C
16.1 °C
15.5 °C
15.1 °C
13.8 °C
13.0 °C
¯0 2 41 Kilometers
Forest Reserve
Natural Area Reserve
National Wildlife Refuge
Island of Hawaii

7. Hawaii Mean Annual Temperature Gradient
800-1600 m (13-18.2 °C)
A model study system:
- Constant plant spp. composition
- Constant disturbance histories
- Constant substrate age & type
- Constant soil water balance
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18.2 °C
17.3 °C
16.7 °C
16.1 °C
16.1 °C
15.5 °C
15.1 °C
13.8 °C
13.0 °C
¯0 2 41 Kilometers
Forest Reserve
Natural Area Reserve
National Wildlife Refuge
Island of Hawaii
Long-term, whole-ecosystem
response to rising MAT

8. Workflow
DNA extraction
(8 samples/MAT plot)
16S rDNA
amplification
454
Pyrosequencing

9. Workflow
DNA extraction
(8 samples/MAT plot)
16S rDNA
amplification
454
Pyrosequencing
Sequence
processing
(QIIME pipeline)
Rarefaction
(2200 seq./sample)
Data analysis
(Diversity, composition)

10. ●
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0
500
1000
1500
2000
13 14 15 16 17 18
Mean annual temperature (°C)
EstimatedOTUrichness
No effect of rising MAT
on OTU richness

11. No effect of rising MAT
on phylogenetic diversity
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0
20
40
60
80
13 14 15 16 17 18
Mean annual temperature (°C)
Phylogeneticdiversity

12. No effect of rising MAT on
composition at phylum level
0
25
50
75
100
13 13.8 15.1 15.5 16.1a 16.1b 16.7 17.3 18.2
Mean annual temperature (°C)
Relativeabundance(%)
Phylum
Proteobacteria
Acidobacteria
Actinobacteria
Chloroflexi
Candidate WPS−2
Planctomycetes
Other

13. Weak effect of rising MAT
on OTU composition
R2 = 0.03, p = 0.07 (PERMANOVA)
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NMDS Axis 1
NMDSAxis2
13
14
15
16
17
18
MAT (°C)

14. Why do soil bacterial communities
remain stable with rising MAT?
Increase in abundance
Increase in activity
Decrease in dormancy
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18.2 °C
17.3 °C
16.7 °C
16.1 °C
16.1 °C
15.5 °C
15.1 °C
13.8 °C
13.0 °C
¯0 2 41 Kilometers
Forest Reserve
Natural Area Reserve
National Wildlife Refuge
Island of Hawaii

15. Conclusions
“Rising tide lifts all boats”
Warming alone may be
insufficient to alter
community structure
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18.2 °C
17.3 °C
16.7 °C
16.1 °C
16.1 °C
15.5 °C
15.1 °C
13.8 °C
13.0 °C
¯0 2 41 Kilometers
Forest Reserve
Natural Area Reserve
National Wildlife Refuge
Island of Hawaii
@biogeocycle