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Determine the vegetation period and regional trends in Germany Wolfgang Janssen wolfgang.janssen@dwd.de

Determine the vegetation period and regional trends in Germany Wolfgang Janssen wolfgang.janssen@dwd.de. Phenology 2010, June. Background: different crops have different growth periods some issues need a general definition of the vegetation period impacts of climate change how to define?

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Determine the vegetation period and regional trends in Germany Wolfgang Janssen wolfgang.janssen@dwd.de

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  1. Determine the vegetation period and regional trends in GermanyWolfgang Janssenwolfgang.janssen@dwd.de Phenology 2010, June

  2. Background: • different crops have different growth periods • some issues need a general definition of the vegetation period • impacts of climate change • how to define? • good reproduction in past years? • any trends? Phenology 2010, June

  3. How to define? • many different approaches with different results • use only temperature as meteorological input • link to definition of the phenological year • vegetation starts in early spring • with plant stages: • forsythia, flowering (25.3.) • gooseberry, leaf unfolding (27.3.) vegetation stops at beginning of winter with plant stages: oak, leaf fall beech, leaf fall (27.10.) Phenology 2010, June

  4. Tsum = start day(Tmean day temperature – Treference temperature) 58 stations with meterological and phenelogical observations large variation of phenological observations in small areas most probable values by interpolation many different relations where tested not the best but simplest relation with good results was taken Phenology 2010, June

  5. for each case optimal temp. sum for 58 stations in 18 years 60 different start dates 30 different ref. temp. (1800 cases) observed phenological dates of 58 stations in 18 years for each case date reaching opt. temp. sum at 58 stations in 18 years difference between observed and calculated dates => dispersion for each case Tsum = start date(Tmean day temperature – Treference temperature) a simple methode to find the optimal start date and reference temperature Phenology 2010, June

  6. dispersion matrix for gooseberry (leaf unfolding) reference temperature day of the year (start date) start date = 49. day of year, reference temperature = 0 °C, sum = 164 °C Phenology 2010, June

  7. a fixed start date or end of dormancy can‘t be correct ! • start date must depend from weather situation • made a test with the both coldest and warmest years warm years same ref. temp. -2.5 °C different start days cold years Phenology 2010, June

  8. determing for every year with a fixed reference temperature of -2.5 °C optimal start date and optimum temperature sum (TScrop) observed fitted dependence correlation 0.87 Phenology 2010, June

  9. as start date is earlier, a higher temperatur sum is required (small chilling) as start date is later, a lower temperatur sum is required (large chilling) • Calculation cheme: • starting at 1.1. • for every following day • calculating TScrop • calculate TSlimit • TS > TSlimit ? no correlation of 0,90 dispersion of 4.3 days yes plant state reached Phenology 2010, June

  10. observed phenological plant state in 2009 calculated phenological plant state in 2009 in mean +0,8 days difference Phenology 2010, June

  11. dispersion matrix for beech (leaf fall, 300. day of year) reference temperature day of the year (start date) start date = 214. day of year, reference temperature = 30 °C, sum = -1383 °C Phenology 2010, June

  12. determing for every year with a fixed reference temperature of 30 °C optimal start date and optimum temperature sum (TScrop) observed fitted dependence correlation 0.99 Phenology 2010, June

  13. with high temperatures end of vegetation is later latest possible end is 18.11. (322. day of year) • Calculation cheme: • starting at 180. day • for every following day • calculating TScrop • calculate TSlimit • TS < TSlimit ? correlation of 0,60 dispersion of 5,1 days no yes plant state reached Phenology 2010, June

  14. observed phenological plant state in 2007 calculated phenological plant state in 2007 in mean +0,4 days difference Phenology 2010, June

  15. Comparison between observed and calculated mean values for Germany Phenology 2010, June

  16. time series for mean vegetation period in Germany 1980 1991 period 2 period 1 8 days longer Phenology 2010, June

  17. calculated vegetation period 1991 - 2009 calculated vegetation period 1961 - 1980 trend Phenology 2010, June

  18. optimal parameter for other plant stages Phenology 2010, June

  19. begin greening of grasland Phenology 2010, June

  20. ref. Temp. = -2,5 °C correlation 0,84 correlation 0,89 mean dispersion 4,5 days Phenology 2010, June

  21. flowering of dandelion Phenology 2010, June

  22. ref. Temp. = -2,5 °C correlation 0,81 correlation 0,89 mean dispersion 4,1 days Phenology 2010, June

  23. apple, flowering correlation of 0,90 and 3,7 days deviation always 24.2. for start day, ref. temp. of 1 °C, temp. sum of 361 °C Phenology 2010, June

  24. Thank you for your attention! Phenology 2010, June

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