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David Stone, IPILPS Workshop ANSTO 18-22 April 2005

Diurnal Cycle Observations of Stable Water Isotopes in the Biosphere. David Stone, IPILPS Workshop ANSTO 18-22 April 2005. IPILPS: isotopes at the land surface. Scientific Hypothesis

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David Stone, IPILPS Workshop ANSTO 18-22 April 2005

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  1. Diurnal Cycle Observations of Stable Water Isotopes in the Biosphere David Stone, IPILPS Workshop ANSTO 18-22 April 2005

  2. IPILPS: isotopes at the land surface Scientific Hypothesis Observation and analysis of the diurnal fluxes of H218O and HDO between the soil, plants and atmosphere can accurately determine the partitioning of precipitation into transpiration, evaporation and total runoff. Method Three ecosystems were selected as study areas Tropical forest, such as the Amazon Basin, Sth America Cool, humid temperate forest, such as Central Europe, or Nth America Warm, dry temperate forest, such as SE Australia Exploit stable water isotopes H218OandHDOto investigate the hypothesis. Observations would be required at Tumbarumba Field data expected to be available for the Amazon, Europe and America

  3. IPILPS Stable Isotope data needs • Data expected to be available include • precipitation • atmospheric vapour • plant (stem and leaf) water • soilwater • groundwater ( not expected to vary significantly) • riverwater • The data will be used within IPILPS to evaluate isotope enabled LSS output:

  4. Overview of presentation • Expected ranges of values • the precipitation input at the three ecosystems • vapour<stem<leaf order of enrichment • Data sets examined • Amazon; Manaus, Santarem and Trinidad • Central Europe; Munich, other German sites • North America; temperate and semi-arid • others

  5. Variation in del 18O (‰) Leafwater 3 to10 ‰ THE WATER CYCLE

  6. Expected isotope ratios for SE Australia (Tumbarumba) Leaves GMWL rainwater Surface water Root zone water = stem water = transpired water 9-10 ‰ Surface evaporate LEL Local vapour 9-10 ‰

  7. 10 ‰ depletion Mean rainfall

  8. Precipitation Input Signal; 3 sites

  9. Munich Vapour and Precipitation Vapour and precipitation lie along a single MWL data source: W. Stichler, unpublished

  10. Munich; vapour/precipitation equilibrium Regression; r2 = 0.7 Delta 18O(p-v) = 8.5‰ data source: W. Stichler, unpublished

  11. IPILPS data requirements and sources • Water isotopologues • del H218O and 1H2H16O (‰) both desired • Comparison of LSS • By output, and against real data • Real field data required at appropriate time scales, monthly, daily, hourly • Prefer data at diurnal timescale • BASIN database; (Ehleringer), Americas • CarboEuroflux; (various), Europe

  12. Data collection methods • Towers fitted with tubing for cryogenic vapour trapping, water kept frozen • Soil and Leaf samples sealed in exetainers; distilled cryogenically before analysis • del D and del O-18 performed by IR-MS

  13. Tropical Rainforest data; Manaus, Amazon Trinidad LBA BASIN sites Manaus Santarem

  14. data source: Matsui et al,1983, Acta Amazonica, 13, 307-68 10‰ enrichment

  15. am pm Enrichment increases during day 10.4 ‰ average enrichment Data source: LBAdatabase (Ometto); submitted for publication Canopy Leaves enriched 11 ‰ 9 ‰ Understory Leaves less enriched

  16. 11 ‰ 9 ‰ Data source: LBA (Ometto); unpublished Dry season vapour, leaf and stem water more enriched 11 ‰ 7 ‰

  17. Data source: LBA (Ometto); unpublished 12- 14 ‰ Inter-annual differences possible? 6 ‰ 11 ‰ Much less leaf enrichment than in previous year

  18. Data source: LBA (Ometto); unpublished 10- 12 ‰ 8 ‰ 8 ‰

  19. Data source: LBA (Ometto); unpublished 10- 13 ‰ 10 ‰ Dry season vapour, leaf and stem water more enriched 9 ‰ Much less leaf enrichment than in previous year 5 ‰

  20. Data source: LBA (Ometto); unpublished Vapour less enriched mid-morning, but more enriched in afternoon 5 ‰ difference in canopy 12 ‰ 8 ‰

  21. Vapour more enriched midday, but less enriched in afternoon 5-10 ‰ difference in canopy Data source: LBA (Ometto); unpublished small difference between vapour and stems!! 12 ‰ 8 ‰

  22. Amazon Forest Vapour daytime variation, June 2000 Data source: LBA (Ometto); unpublished Vapour less enriched mid-morning, but more enriched in afternoon Vapour more enriched midday, but less enriched in afternoon

  23. Amazon Forest Vapour Keeling Plot analysis, June 1995 Data source: Leo Sternberg, IAEA 2004

  24. Amazon Forest Vapour Keeling Plot analysis, May - Dec 1995 Data source: Leo Sternberg, IAEA 2004

  25. Average precip, calc

  26. Conclusions • Amazon • Leaf enrichment increases during day • Canopy Leaves enriched, understory much less so • Stem water enriches slightly in dry season • Dry season vapour, leaf & stem water more enriched • Vapour<Stem<Leaf enrichment close to optimum • Keeling plot analysis, 18O, indicates transpiration predominant flux of return vapour to atmosphere

  27. Cool Temperate; Munich, Germany Jena and Dresden CarboEuroFlux sites

  28. data source: W. Stichler, unpublished

  29. data source: W. Stichler, unpublished

  30. data source: W. Stichler, unpublished

  31. Munich Vapour and Precipitation data source: W. Stichler, unpublished

  32. Samples taken in evening 19:00-23:00 Leaf water depletes overnight Stem and soilwater: little variation

  33. Leaf water depletes summer to winter Stem and soilwater show little variation

  34. Leaf water depletes summer to winter Stem and soilwater show little variation

  35. Cool Temperate; Ottawa and Oregon BASIN sites Ottawa Oregon sites Oklahoma Arizona

  36. 10 ‰ enrichment data source: Flanagan, L.B. and Varney, G.T. 1995, Oecologia 101:37-44

  37. Leafwater enriched during daytime 10 ‰ enrichment Average precip, calc

  38. Average precip, calc

  39. Shallow soilwater deeper soilwater Average precip, calc

  40. 13 ‰ enrichment Average precip, calc

  41. Conclusions • Europe • Leaf enrichment decreases during evening (6-11pm) • Stem, roots, soil and litter show small variations, but little systematic seasonal change • Vapour<Stem<Leaf enrichment less than optimum • Humid North America • Soilwater data have a large variation • Forest stem<leaf enrichment at optimum • Grassland stem<leaf enrichment at optimum • Forest and Grassland vapour<stem enrichment less than optimum ( Summer data only available)

  42. Warm Temperate - semi arid regions; Israel, Arizona

  43. Average precip

  44. Depletion during daytime

  45. GMWL LEL

  46. Conclusions • Semi-arid Israel and North America • Israel: vapour<stem<leaf enrichment at optimum • Arizona: vapour became depleted during the day • Keeling plot analysis, using both 2H and 18O indicates transpiration predominant flux of return vapour to atmosphere

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