1. Chronosequence of soil respiration in ChEAS sites (sub-topic of spatial upscaling of carbon measurement) Jim Tang Department of Forest Resources University of Minnesota jtang@umn.edu

2. Factors for simulating long-term forest carbon dynamics Natural variability and disturbance Human disturbance and management Climate change: T, precipitation… Increasing atmospheric CO 2 concentration and nitrogen deposition -- fertilization Forest succession

3. Why chronosequence Our knowledge in understanding the influence of forest succession on carbon dynamics is limited. Most long-term carbon simulation models do not consider forest succession as a variable.

4. Forest stands with different ages Old-growth Mature YoungClear-cut

5. Soil respiration measurement

6. Soil temperature

7. Chronosequence of soil respiration in response to temperature YA: Young aspen IA: intermediate aspen MH: mature hardwood OG: old- growth

8. Chronosequence of soil respiration

9. Chronosequence of soil carbon content, annual change of soil carbon, and nitrogen content

10. YA: young aspen, IA: intermediate aspen. MH: mature hardwood, OHD: old-growth hardwood, OHL: old-growth hemlock Tang et al., 2006. Agri. For. Met., in press Cumulative respiration and components

11. Odum, 1969, ScienceRyan et al. 1997, Ad. Eco. Res. Successional pattern of carbon flux: two conceptual models

12. Simulate long-term large-scale soil carbon Century model

13. Published work

14. Eddy Covariance vs. chamber measurements Tang et al., 2006. Agri. For. Met., in press

15. Sap flow vs. tower measurement of water flux Tang et al., 2006. J. Geophys. Res.- Biogeosciences E C = 65% E T in the growing season

16. Water use efficiency (WUE = GPP/E C ) response to D (VPD) Tang et al., 2006. J. Geophys. Res.- Biogeosciences

17. Work in progress

18. Diurnal patterns of soil respiration Year 2005 Validate nighttime eddy covariance data, and correspondingly, daytime GPP; Parameterize the soil respiration model. Year 2006