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Effects of Forest Thinning on Soil CO2 Efflux at Catamount Institute: A Study on Global Carbon Cycle

Our study investigated the impact of forest thinning on soil CO2 efflux at Catamount Institute, analyzing factors like litterfall, root respiration, and temperature. Results showed higher efflux in thinned plots, emphasizing the importance of managing carbon flux in forest ecosystems.

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Effects of Forest Thinning on Soil CO2 Efflux at Catamount Institute: A Study on Global Carbon Cycle

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  1. Effects of Forest Thinning on CO2 Efflux Peter Erb, Trisha Thoms, Jamie Shinn Biogeochemistry 2003: Block 1

  2. Our project… Measured soil CO2 efflux at the Catamount Institute in both control and thinned plots, using the Li-Cor 6200.

  3. Aim of Study To understand the effects of forest thinning on CO2 efflux at the Catamount Institute.

  4. 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.

  5. Why study CO2 efflux? • Soil CO2 efflux produces 10 times more atmospheric CO2 than fossil fuels.

  6. Concern that respiration and decomposition rates will increase exponentially, accompanied by a linear growth rate of plant biomass.

  7. Positive Feedback Cycle Temperature Global Warming Decomposition CO2 efflux

  8. Hypothesis Control plots will have a higher CO2 efflux due to more litterfall and greater root density.

  9. 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

  10. T-test: Total plots showed significance, within 90% confidence. P = .08 Hotspots: Plot one is driving total.

  11. Results T-test: Total plots showed significance, within 95% confidence. P=.02

  12. Results Low correlation: .0348 Log scale: .027

  13. Results Importance of slope Correlation significant: .2486

  14. Discussion Results differ from hypothesis: Thinned CO2 efflux is greater than control Investigate major components of CO2 efflux: -Litterfall -Root respiration -Temperature

  15. 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?

  16. Root Respiration • Contributes to efflux: • Site of plant respiration • 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

  17. Temperature • Warm temperatures stimulate microbial activity and root respiration • Thinned: open canopy, sunlight warms soils • Temperature seems to have greatest impact in this ecosystem on CO2 efflux

  18. 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

  19. 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

  20. 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

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