The Impact of Site Extremes on the Onset of Phenological Phases of Selected Tree Species

Abstract

In the years 2007–2013 we performed phenological observations of common hazel (Corylus avellana L.), blackthorn (Prunus spinosa L.), and hawthorn (Crataegus oxyacantha L.) at two locations of central Slovakia situated at elevations of 300 m and 530 m a.s.l. The phenophase of first leaves of all tree species started in the second half of April on average, and was conditioned by the average daily air temperatures above 0 °C. The earliest onset was observed at both locations in 2007 due to the highest average air temperature during the observed period, which in March reached the value of 6.1 °C. Colouring of leaves started in the second and third decades of September. Both phenophases began earlier at the location situated at the higher elevation due to the effect of aspect, terrain, and soil depth. During the last 7 years, the average length of the growing season of tree species situated at an elevation of 300 m was from 136 to 152 days, in more extreme conditions at an elevation of 530 m the growing season was shorter by 12 days in the case of blackthorn and by 5 days in the case of hawthorn.

Keywords

• phenology
• central Slovakia
• forest tree species
• site extremes