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Water use and water use efficiency in west coast Douglas-fir

BC FLUX STATION. CFCAS. Water use and water use efficiency in west coast Douglas-fir. Paul Jassal, Andy Black, Bob Chen, Zoran Nesic, Praveena Krishnan and Dave Spittlehouse University of British Columbia Vancouver, Canada . 1. BC Flux Station sites. Campbell River. Vancouver.

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Water use and water use efficiency in west coast Douglas-fir

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  1. BC FLUX STATION CFCAS Water use and water use efficiency in west coast Douglas-fir Paul Jassal, Andy Black, Bob Chen, Zoran Nesic, Praveena Krishnan and Dave Spittlehouse University of British Columbia Vancouver, Canada

  2. 1. BC Flux Station sites Campbell River Vancouver Outline of the talk 2. Diurnal, seasonal and interannual variability of water use and water use efficiency 3. Relationships betweenphysiologicaland environmental controls of water use and carbon uptake 4. Effect of stand age 5. Effect of nitrogen fertilization

  3. BC Flux Station Chronosequence of three coastal Douglas-fir stands Plantation HDF00 Pole/sapling HDF88 Near mature DF49 Height (m) 2 8 33

  4. Water use efficiency Water use or evapotranspiration (E) = mm or kg of water m-2 Water use efficiency= g C m-2 mm-1 or g C kg-1 water as GPP/E or NEP/E GPP = gross primary productivity, i.e., C uptake by photosynthesis (~twice of NPP) NEP = net ecosystem productivity (net C sequestration) = GPP – R In this analysis, EC-measured fluxes have not been corrected for energy balance closure. EBC is approximately 0.81.

  5. Physiological and environmental controls Available energy Penman-Monteith equation: Vapor pressure deficit Aerodynamic conductance Canopy conductance Priestley-Taylor equation: Both C uptake by and transpiration from vegetation takes place through leaf stomata with their rates partly determined by canopy conductance, gc.

  6. Air temperature C C Month

  7. Dry months Cumulative precipitation mm J F M A M J J A S O N D

  8. Soil water content in the 0-60 cm layer FC m3 m-3 WP Dry months Month

  9. 24 GPP mol C m-2 s-1 12 0 0.08 E g m-2 s-1 0.04 0 2 PAR mmol m-2 s-1 1 0 2 D kPa 1 0 8 mm s-1 4 0 11 12 13 14 15 16 17 August 2006 Diurnal variations gc

  10. Seasonal variations 15 GPP 10 g C m-2 d-1 5 0 E 2 mm d-1 1 0 20 WUE g C m-2 mm-1 or g C kg-1 10 0 J F M A M J J A S O N D 2006

  11. Seasonal variations in GPP, E and WUE GPP g C m-2 mon-1 E mm mon-1 WUE g C m-2 mm-1 Or g C kg-1 Month

  12. Relationship between monthly GPP and E GPP (g C m-2 mon-1) GPP = 6.0E –25 r2 = 0.96

  13. Cold Septembers Effect of soil moisture on monthly E 1998 - 2007 Wet months Dry months mm mon-1

  14. Cold Septembers Effect of soil moisture on monthly GPP 1998 - 2007 Wet months Dry months g C m-2 mon-1

  15. Relationship between monthly E and net radiation E(mm water mon-1) E = 0.1Rn + 11 r2 = 0.94

  16. Daytime dry-foliage Priestley-Taylor  Correcting for EBC would result in a 25% increase in  Month

  17. Daytime dry-foliage canopy conductance mm s-1 mm s-1 5 mm s-1 ~ 220 mmol m-2 s-1 Month

  18. Relationship between daytime dry-foliage monthly  and gc 1998 - 2007 + 0.3 

  19. Modelling daytime dry-foliage monthly gc 1998 - 2007

  20. Dry Warm Cold & wet Interannual variations in GPP, E and WUE GPP g C m-2 mon-1 E mm mon-1 WUE g C m-2 mm-1 or g C kg-1 Mean: 5.3 g C kg-1 water

  21. Effect of stand age and fertilization on annual E 500 400 (mm) 300 E Annual 200 Filled triangles are for 2007, the first year after N fertilization 100 0 0 10 20 30 40 50 60 Age (years) Age (Years)

  22. Effect of stand age and fertilization on annual GPP Filled triangles are for 2007, the first year after N fertilization Age (years)

  23. Effect of stand age and fertilization on annual WUE Filled triangles are for 2007, the first year after N fertilization Age (years)

  24. Effect of stand age and fertilization on annual NEP C Sink C Source NEP = GPP - R Age (years)

  25. Effect of stand age and fertilization on annual WUE based on NEP Filled triangle are for 2007, the first year after N fertilization Age (years)

  26. Conclusions • Growing season Priestley-Taylor daytime  of about 0.6 was • consistent with low canopy conductance (~4.5 mm s-1), and • suggests stomatal limitation to transpiration. • Daytime canopy conductance could be parameterized as a • linear function /D. • Water deficit in Jul-Sep decreased E as well as GPP, and • explained much of their interannual variability. • The high correlation between E and GPP resulted in WUE • being relatively conservative with a value of ~5 g C kg-1 water. • There was relatively small 1st year response of GPP & E to N • fertilization; NEP in all 3 stands responded to fertilization, due • to decreased R, resulting in increased WUE on an NEP basis.

  27. Thank you!

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