Results Importance of slope Correlation significant:.2486
Discussion Results differ from hypothesis: Thinned CO 2 efflux is greater than control Investigate major components of CO 2 efflux: -Litterfall -Root respiration -Temperature
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?
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
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 CO 2 efflux
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
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
Conclusion CO 2 Efflux higher in thinned: due to high soil temperature Litter quality, quantity, and root biomass may not differ Loss of CO 2 sink Future Research Management implications for upper montane mixed conifer
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