Characteristics of vegetation season in Szymbark in the period 1968–2009
The paper presents the characteristics of the vegetation season in Szymbark based on the average daily air temperature recorded at the Research Station in Szymbark, IG&SO PAS, in the period 1968–2009. Based on the five-day consecutive curve and 6 degree polynomial offset curve, the dates of passing the threshold value of air temperature of 5 °C were determined. The data obtained were analyzed statistically and classified into 5 classes on the start date, end date, duration and temperature, basing on standard deviation values. The number of years in an individual class allow to calculate the occurrence frequency of vegetation periods of a specific type, attributed to a given class. The average duration of vegetation season was 222 days (varied from 174 to 250 days). Growing season average started on March 31 and ended on November 6 and it had tends to end later about 0,8 day per 10 years and about 0,7 days per years elongate the duration of growing season. The average temperature during the growing season was 13,3 °C and had an upward trend (r = 0,59). It was found that the increase in average annual air temperature by 1 °C will extend the growing season by 9,5 day. The highest percentage in class D, with late the end of vegetation, long period and warm growing season may be a reference to the observed upward trend in air temperature, indicating a warming climate.