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Chronosequence of soil respiration in ChEAS sites

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. Factors for simulating long-term forest carbon dynamics. Natural variability and disturbance

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Chronosequence of soil respiration in ChEAS sites

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  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 CO2 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 Clear-cut Young Mature Old-growth

  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. Cumulative respiration and components 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

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

  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 EC = 65% ET in the growing season Tang et al., 2006. J. Geophys. Res.-Biogeosciences

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

  17. Work in progress

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

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