Climate Change Impact on Duration of Vegetative Period of Five Deciduous Tree Species

Abstract

The air temperature is directly linked to the plant growth season, affecting the timing of the start and the end of the vegetative period and its duration. The aim of this study was to analyse the impact of changing climatic parameters on the duration of the vegetation period in 1956-2008 of five deciduous tree species (oak - Quercus robur L., maple - Acer platanoides L., lime - Tilia x vulgaris Hayne, birch - Betula pendula Roth. and ash - Fraxinus excelsior L.) growing in Kaunas Botanical Garden of Vytautas Magnus University. The duration of the vegetative period (number of days) was calculated between the dates of the beginning of bud swell and the end of leaf fall phenophases. Mean length of the vegetative period in 1956-2008 of observed tree species varied from 186 for ash to 214 days for birch. The beginning of the bud swelling phenophase advanced on average from 1 (oak) to 14 days (ash) in 1956-2008. The beginning of the bud swelling phenophase was significantly related to the temperature of February (for lime, birch and ash) and March (for all species). The end of the leave fall phenophase was delayed on average from 3 (birch) to 25 days (maple) in 1956-2008. In most cases, the end of a leave fall phenophase was not significantly related to climatic parameters, however the temperature of September had a significant positive impact (higher temperature determining later leave fall date) on maple, lime and ash. The duration of the vegetative period of deciduous tree species depended mostly on the warming late winter - early spring temperature (February-April) and for some species  - on the warming late summer temperature (in August), while changes in the amount of precipitation had little effect. Among the observed species the duration of the maple vegetative period was the most and that of oak was the least sensitive to climate warming.