Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003:...
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Transcript of Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003:...
![Page 1: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/1.jpg)
Effects of Forest Thinning on CO2 Efflux
Peter Erb, Trisha Thoms, Jamie Shinn
Biogeochemistry 2003: Block 1
![Page 2: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/2.jpg)
Our project…
•Measured soil CO2 efflux at the Catamount Institute in both control and thinned plots, using the Li-Cor 6200.
![Page 3: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/3.jpg)
Aim of Study
•To understand the effects of forest thinning on CO2 efflux at the Catamount Institute.
![Page 4: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/4.jpg)
What is CO2 efflux?
• Rate of CO2 released from soil. (gC/m2s)
• Caused by microbial, soil animal and root respiration.
• Important part of global C cycle.
![Page 5: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/5.jpg)
Why study CO2 efflux?
• Soil CO2 efflux produces 10 times more atmospheric CO2 than fossil fuels.
![Page 6: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/6.jpg)
• Concern that respiration and decomposition rates will increase exponentially, accompanied by a linear growth rate of plant biomass.
Soil Respiration and NPP v. Temperature
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10
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30
40
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0 2 4 6 8 10 12
Temperature
NPP
soil respiration
![Page 7: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/7.jpg)
Positive Feedback Cycle
Temperature
DecompositionCO2 efflux
Global Warming
![Page 8: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/8.jpg)
Hypothesis
•Control plots will have a higher CO2
efflux due to more litterfall and greater root density.
![Page 9: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/9.jpg)
Methods Study site: Catamount upper montane mixed conifer. Plots 1-3
divided into thinned & control.
Technique: Li-Cor 6200 (infrared absorption)
Field process
Statistical analysis: T-test
Graphical analysis
![Page 10: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/10.jpg)
T-test: Total plots showed significance, within 90% confidence.
P = .08
Hotspots: Plot one is driving total.
Carbon Efflux: Thinned vs. Control
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4060
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Plot 1 Plot 2 Plot 3 Total Plots
Carbon Efflux (µgC/m^2s)
Control
Thinned
![Page 11: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/11.jpg)
Results
T-test: Total plots showed significance, within 95% confidence. P=.02
Soil Temperature: Thinned vs. Control
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5
10
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Plot 1 Plot 2 Plot 3 Total PlotsSoil Temperature (C)
Control
Thinned
![Page 12: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/12.jpg)
Results
Low correlation: .0348
Log scale: .027
CO2 Efflux vs. Soil Temperature
R2 = 0.0348
0204060
80100120140
0 5 10 15
Soil Temperature (C)
CO2 Efflux (µgC/m^2s)
Carbon Efflux(µgC/m^2s)
Expon. (Carbon Efflux(µgC/m^2s))
![Page 13: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/13.jpg)
Results
Importance of slope
Correlation significant: .2486
CO2 Efflux vs. Slope
R2 = 0.2486
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10
20
30
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50
60
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15 20 25 30 35 40
Slope (degrees)
Average CO2 Efflux
(µgC/m^2s)
CO2 Efflux
Linear (CO2 Efflux)
![Page 14: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/14.jpg)
Discussion
Results differ from hypothesis: Thinned CO2 efflux is greater than control
•Investigate major components of CO2 efflux:
-Litterfall
-Root respiration
-Temperature
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Litterfall• Soil respiration is directly related to
aboveground litterfall• Thinned sites: fewer trees, less litterfall
However…
•Thinning occurred ~20 years ago•Time for re-growth•Species composition: higher quality litter in thinned?
![Page 16: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/16.jpg)
Root Respiration• Contributes to efflux:
1. Site of plant respiration
2. Highly decomposable fine roots
• Thinned sites: fewer trees, less root respiration
Considerations…•Re-growth period•Root expansion due to low nutrient availability•Root density may not differ much
![Page 17: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/17.jpg)
Temperature• Warm temperatures stimulate microbial
activity and root respiration• Thinned: open canopy, sunlight warms soils
Carbon Efflux: Thinned vs. Control
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Plot 1 Plot 2 Plot 3 Total Plots
Carbon Efflux (µgC/m^2s)
Control
Thinned
Soil Temperature: Thinned vs. Control
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10
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Plot 1 Plot 2 Plot 3 Total PlotsSoil Temperature (C)
Control
Thinned
•Temperature seems to have greatest impact in this ecosystem on CO2 efflux
![Page 18: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/18.jpg)
Soil Moisture• Thinned sites are drier
• Reduces decomposition, but slows NPP more
• Speed decomposition with temperature, while slowing NPP with reduced water…
Positive Feedback Loop!-Carbon sinks cannot keep up with C flux to the atmosphere
![Page 19: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/19.jpg)
Spatial and Temporal Heterogeneity
Things to Consider
• Recently thinned forests v. our study site• Diurnal fluctuations• Slope• Hotspots: - location relative to vegetation
- exposure to sunlight - ground cover
All these factors contribute to great uncertainty
![Page 20: Effects of Forest Thinning on CO 2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1.](https://reader030.fdocuments.in/reader030/viewer/2022032701/56649c7c5503460f9493175d/html5/thumbnails/20.jpg)
Conclusion
• CO2 Efflux higher in thinned: due to
high soil temperature
• Litter quality, quantity, and root
biomass may not differ
• Loss of CO2 sink
• Future Research
• Management implications for upper
montane mixed conifer