1. Dennis Baldocchi, Jianwu Tang & Liukang Xu
Separation of ‘Autotrophic’ and ‘Heterotrophic’ Respiration in an Oak-Grass Savanna and their Link with Canopy Photosynthesis
Dennis Baldocchi, Jianwu Tang & Liukang Xu
Biometeorology Lab
Dept Environmental Science, Policy and Mgt
University of California, Berkeley
CarboEurope, Crete, 2006

2. Outline Introduction Methods Results and Discussion
Quantifying Roles of Lags, Pulses and Switches
Objectives
Methods
Site Description
Continuous Soil CO2 Measurements
Flux-gradient measurements
Results and Discussion
Responses to temperature, rain pulses and photosynthetic activity
Test with Eddy Covariance

3. Partitioning Soil Respiration: Principles
Kuyzakov 2006

4. Measure Soil Temperature at the location of the source

5. Girdling Experiment of Hogberg et al. 2000

6. Experimental Treatments
Under a Tree:
~Ra+Rh
Open Grassland:
~Rh (summer)

7. Tonzi Ranch/Oak Savanna

8. Vaisala GMT 220

9. Continuous Soil Respiration with soil CO2 Sensors
[CO2] must be corrected for temperature

10. Theory/Equations Moldrup et al. 1999
Fcp: fraction silt and sand; b: constant; f:porosity;
e: air-filled pore space

11. Validation with Chambers

12. Validation with EC
Gophers, moved probe d129

13. Results and Discussion

14. CO2 in the Soil: Between and Under a Tree

15. What Happens After Rain?
Microbial Stimulation
It occurs for 4 days, until the soil dries
Evacuation of Pores
cannot be sustained for several days

16. Effects of temperature, soil moisture, rain and photosynthesis on CO2 Efflux

17. When Does Root Respiration Initiate?:
Prior, Coincident or After the Start of Photosynthesis
Canopy Ps starts ~d80
Rauto starts ~d100

18. Temperature: hysteresis and lags

19. Why?: Respiration Lags Photosynthesis, v1: Hourly Scale

20. Continuous Measurements Enable Use of Inverse Fourier Transforms to Quantify Lag Times

21. Respiration Lags Photosynthesis, v2: Daily Scale

22. Biometeorology Team Liukang Xu Jianwu Tang Ted Hehn
Funding: US DOE/TCP; WESTGEC/NIGEC;
Kearney Soil Science Found.,Ca Ag Expt Station, AmeriFlux