Hamburg forsythia calendar

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Forsythia at the Lombard Bridge

The Hamburg forsythia calendar is the phenometric record of the times at which the forsythia bushes began to bloom on the Lombard Bridge in Hamburg since 1945.

The beginning of flowering of the frost-sensitive forsythia is an indicator for the first spring and has been part of the phenological observations of the German Weather Service (DWD) since 1952 . The Hamburg Lombard Bridge is the longest continuous series of observations known to the DWD.

history

In destroyed Hamburg, shortly before the end of the Second World War , Carl Wendorf noticed the blooming forsythia bushes amid the rubble on the Lombard Bridge on March 27, 1945. He decided to note the beginning of flowering every spring, which led to a complete record from 1945 onwards. Jens Iska-Holtz has continued this list since Carl Wendorf's death in 1984. He reports the data as a phenological observer to the German Weather Service.

Beginning of flowering

The earliest forsythia bloom on Hamburg's Lombard Bridge was on February 15th in 2002, and the latest in 1970 on April 25th. The year-to-year difference was greatest from April 15, 1987 to February 17, 1988. In 1995 the DWD found that the Lombard Bridge showed the strongest trend of all locations with a phenological data series with an early advance of 26 days in 50 years. In 2015, too, the DWD constant for the period between 1945 and 2014 a trend towards an earlier start of flowering, which is weaker than the trend 1945–1995.

An earlier start of flowering is usually associated with higher temperatures in the preceding months. Forsythia bloom was clearly premature between 1945 and 2006 - along with higher temperatures in the months before blooming began. Without sufficient cold stimulus in winter, however, forsythia does not necessarily follow temperature (→ vernalization ). In the winter of 2006/2007 there was a maximum temperature at the Lombard Bridge, but the forsythia bloomed relatively late, well after its record level in 2001/2002, because there was no cold stimulus in the warm winter of 2006/2007.

Climate indicator

The premature forsythia bloom is an indicator of climate changes at the site. In addition to global warming, other changes in environmental influences in this urban location should also be considered as the cause of changes in the beginning of flowering. Including mesoclimatic developments: A study of urban conurbations from the year 2000, which took into account the forsythia bloom in Hamburg, showed that early spring came about four days earlier in the cities examined than in the surrounding area. The trend towards an earlier onset of early spring was weaker in metropolitan areas than in rural regions.

In its climate impact monitoring in the field of agriculture, the City of Hamburg uses the beginning of the forsythia bloom on the Lombard Bridge as an indicator for long-term changes in vegetation development. All indicators of the indication field “Phenological changes” - in addition to the beginning of flowering of the forsythia, these are also that of the apple and the beginning of thermal vegetation - indicate an early start of vegetation in the Hamburg metropolitan region.

Web links

Individual evidence

  1. ↑ Jens Iska-Holtz and the secret of the forsythia blossom . In: Hamburger Abendblatt . Hamburg March 19, 2004 ( abendblatt.de ).
  2. ↑ Spring is when the forsythias bloom . In: Welt am Sonntag . Berlin March 4, 2012 ( welt.de ).
  3. ↑ a b German Weather Service: Forsythia calendar for the "Hamburger Lombardsbrücke" location 1945 to 2018. Accessed on April 14, 2018.
  4. ↑ a b 50 years Hamburg forsythia calendar . In: German Weather Service (Ed.): Phenology Journal . No.  January 03 , 1995.
  5. ^ Deutscher Wetterdienst (Ed.): Regulations and operating documents for the phenological observers of the German Weather Service . VuB 17. Offenbach am Main 2015, section » Forsythia, hanging forsythia, gold lilacs ( dwd.de [PDF; 17.1 MB ]).
  6. ^ E. Bruns: Phenological observation networks today and yesterday . In: Deutscher Wetterdienst (Ed.): Promet - meteorological training . Volume 33, No. 1/2 , 2007, pp. 3 ( dwd.de - based on the five-year moving average of the temperature 90 days before the start of flowering at the Hamburg-Fuhlsbüttel weather station).
  7. ^ Deutscher Wetterdienst (Ed.): Regulations and operating documents for the phenological observers of the German Weather Service . 2015, section » Forsythia, hanging forsythia, golden lilac :“ If there is no sufficient cold stimulus, the forsythia flower does not necessarily “follow” the temperatures. Winter 2006/2007 is a good example. In spite of a maximum temperature, the forsythia on the Hamburg Bridge of Lombards bloomed clearly after its "record value" of 02.15.2002 "
  8. ^ A b Hans von Storch , Martin Claussen: Climate report for the Hamburg metropolitan region . Springer, 2012, ISBN 978-3-642-16035-6 , 6.2.1 Plants and Climate Change: Ecophysiology, Phenology, Limits of Distribution and Biotic Interactions.
  9. ↑ City of Hamburg, Ministry of Environment and Energhie (ed.): Data Sheet for IMPACT Indicator beginning of vegetation (LW-I-2) . September 2016 ( hamburg.de [PDF; 446 kB ]).