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| Titel |
Changes of growing season in Latvia |
| VerfasserIn |
Gunta Kalvane, Agrita Briede, Lita Lizuma |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250040602
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| Zusammenfassung |
| To investigate the changes of growing season the study uses phenological and climatological
data in Latvia for the period 1971- 2000.
The phenological calendar method was applied. Changes of growing seasons were
described using data about 2 phenological phases in 6 observation points (voluntary
collected data) and also climatological data of closest meteorological stations for each
site. The growing season was described using the birch Betula pendula and maple
Acer platanoides as an example. The duration of the growing season, defined as
the time between leaf onset (BBCH 61) and beginning of leaf colouring (BBCH
92).
The growing season by climatological data for each site was calculated as the number of
days with mean temperatures above 5ºC. Correlation analysis, linear regression and
non-parametric Mann - Kendall trend tests were applied to establish the relationship between
phenological phases and climatological data. The phenological dates given refer to day of the
year, but phenological phases are in BBCH codes.
The greatest increases in average air temperature in Latvia have been recorded in the
spring (March, April and May) and the early winter (November and December).
The average growing season for birch and maple started on 2 May, the end dates of the
growing season are 21 September for maple and 23 September for birch. The average
duration of the growing season for birch was 144 days and 143 for maple. The shortest
average growing season record was 126 days (in 1981) for birch, 129 days (in 1979; 1981) for
maple and the longest season was 158 days (in 1983; 1990) for birch and 172 days for maple
in 1997.
The results indicate a statistically significant trend toward earlier onset of the spring
phases and starts of growing season (r varies from -0.33 to -0.55; in all stations results of the
Mann-Kendall trend are significant (test statistic -¤ -1.65). Within the study period, the
beginning of the growing season advanced by 4.6 to 5.6 days per decade. The study confirms
expressed tendency that on average the onset of phenological autumn in Latvia starts earlier
and therefore increases of growing season referable to spring phase. The length of growing
season for maple is increase by 3.6 days per decade and by 6.4 days per decade for
birch.
Also significant changes in the start, end and duration of growing season considering
climatological observations during 20th century have been observed. At the same time for the
period 1971-2000 there is seen rather high variability in annual length of growing season
according to climatological data.
This study is partly supported by the European Social Fund project No. 2009/ 0138/ 1DP/
1.1.2.1.2/ 09/ IPIA/ VIAA/ 004. |
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