© 1991 Heron Publishing—Victoria, Canada
The utilization of old phenological time series of budburst to compare models describing annual cycles of plants
Pertti Hari (1) and Risto Häkkinen (2)
1. University of Helsinki, Department of Silviculture, Unioninkatu 40 B, SF-00170 Helsinki, Finland / 2. The Finnish Forest Research Institute, Department of Mathematics, Unioninkatu 40 A, SF-00170 Helsinki, Finland / Received July 17, 1990
Summary
A phenological time series of the date of budburst of birch (Betula pendula) was constructed using data from the years 1907–1950. Data for the years 1908, 1910–1915 and 1930 are missing. The phenological
observations were made at Saarijärvi (62°42′ N, 25°44′ E) in Central Finland. Different models describing the rate of development
in the spring were analyzed using temperature data from the city of Jyväskylä about 60 km to the southeast of Saarijärvi.
The models based on temperature sum gave more accurate predictions of the date of budburst than the model based on time. Differences
between different development rates seemed to be negligible when computing the temperature sum.
