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Ecosystem Water Use: A Concept Linking Water and Carbon Fluxes

Ecosystem Water Use: A Concept Linking Water and Carbon Fluxes. Jiquan Chen. Landscape Ecology & Ecosystem Science (LEES) Lab University of Toledo. Feb. 21, 2005. Flux Towers. NEE c & NEE H2O.

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Ecosystem Water Use: A Concept Linking Water and Carbon Fluxes

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  1. Ecosystem Water Use: A Concept Linking Water and Carbon Fluxes Jiquan Chen Landscape Ecology & Ecosystem Science (LEES) Lab University of Toledo Feb. 21, 2005

  2. Flux Towers

  3. NEEc & NEEH2O

  4. Average diurnal fluxes of CO2 and H2O in Jul., Aug., and Sept. in 1999 in a 20 and a 500 year-old Douglas-fir forest (WA). Only data from good fetch (200-310o) directions were used. Negative and positive values indicate uptake and loss, respectively. Chen et al. 2002

  5. Measurement Year 1998 1999 Stand 40YR 450YR 20YR 450YR Carbon (g C.m-2.day-1) July -4.27 1.39 -0.56 -0.79 August -2.69 -0.79 -0.01 -1.10 September -1.21 0.93 -0.33 -1.97 Overall -2.76 0.51 -0.30 -1.26 Water (mm.day-1) July 1.15 0.87 1.67 2.09 August 1.20 1.43 1.36 2.98 September 0.87 1.58 1.02 1.74 Overall 1.15 1.29 1.35 2.30 Average daily net exchange of carbon and water in Jul., Aug., and Sept. of 1998 and 1999 at three Douglas-fir forests of different ages (20, 40, and 450 year-old) in S. WA. Chen et al. 2002

  6. WUE is traditionally used as the amount of photosynthetic product produced per unit water evaporated, but a number of other definitions have been given to this term as well, depending on the purposes of the experiment. In this study, we define WUEe as the ratio of net ecosystem exchange of carbon (Fc) to evapotranspiration (ETor FH2O):

  7. Dry year Wet year Ecosystem Water Use Efficiency (WUEe) at Four Measuring Periods of 3 Douglas-fir Stands

  8. Conclusions Dry year Wet year • WUEe of the old-growth forest was significantly greater in the drier summer of 1998 (2.7 mg.g-1) than in 1999 (1.0 mg.g-1). • WUEe of the young stand was significantly lower than that of old-growth forest.

  9. Scanlon and Albertson 2004

  10. A landscape is composed of a variety of ecosystems differing in type, age, size, shape, and spatial arrangement. Two questions are: • How does WUEe change with stand age (succession)? • How does WUEe vary among ecosystems (disturbance)?

  11. Methods A combination of direct measurements, remote sensing images, and ecosystem models. Pine Barrens Mature red pine Mature hardwood

  12. Young red pine Mature red pine

  13. Cumulative seasonal evaportranspiration (ET) at five ecosystems MRP YRP PB MHW CC

  14. WUE, mg CO2 g-1 H2O WUEe of Five Ecosystems in the CNF of Northern WI R

  15. WUEe among 5 ecosystems

  16. Water use efficiency and stand age

  17. At leaf level, instantaneous water use efficiency is defined as In this paper, we defined ecosystem water use, ,

  18. Water use efficiency by RS community A revisit of WUEe concept:

  19. NCE Influence on Rh: Hardwoods

  20. NCE Influence on Rh: Red Pine

  21. There seems a strong correlation with stand age and ecosystem type!

  22. What’s next? • Is (Ra/ET) varying with age & disturbance? • WUEe in non-growing season equals to (Ra/E)! • How is Ra regulated by biomass (LAI), temperature, and moisture? • How does (NPP*WUE/GPP) vary with time scale (i.e., hours-years)? • How does (NPP*WUE/GPP) change with sucession and disturbance?

  23. Summary of growing season NEE for comparable pine ecosystems of various age classes. Data is from Baldocchi et al. 1997, Joiner et al. 1999, Pypker & Fredeen 2002, Griffis et al. 2003). Euskirchen et al. (in revision)

  24. Hypothesized carbon flux of forest ecosystems after a disturbance

  25. Questions? Support provided by the National Science Foundation, Southern Global Change Program, and WESTGEC of DOE http://research.eeescience.utoledo.edu/lees/

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