Phenological phases of trees on the intensive forest monitoring plots in Slovenia

Study of developmental stages of forest trees in a long time series is of increasing importance for determination of interdependence between meteorological variables and the associated biological responses. In our study we analyzed the needle appearance and leaf unfolding of conifers and deciduous trees and the autumn colouring for broad-leaved tree species. We considered the phenological phases for oak (Quercus robur L.) in research plots Krakovski gozd and Murska šuma, beech (Fagus sylvatica L.) in research plots Lontovž, Temenjak, Borovec, Fondek, Gorica; spruce (Picea abies (L.) Karst.) in research plots Kladje and Krucmanove Konte; Scotch pine (Pinus sylvestris L.) in the research plot Brdo, black pine (Pinus nigra Arnold) in the research plot Gropajski bori. On average, the needle appearance (BGS) of spruce started on the 166th Julian day. BGS of Scotch pine started on the 128th Julian Day, BGS of black pine on the 149th Julian day, respectively. The leaf unfolding (BGS) for beech started, on average, on the 128th Julian day and BGS for oak on the 117th Julian day, respectively. The autumn colouring(EGS) for beech, on average, started on the 297th Julian day, for oak on the 308th Julian day. It was assessed that BGS possibly commenced earlier for spruce, Scotch pine and black pine in all research plots during the 2004 to 2011 period. However, earlier BGS for beech and oak was noticed only in limited number of pots. Later EGS for beech could be confirmed in only two plots (Borovec in Gorica), whereas changes in EGS for oak were later only in plot Murska Šuma. There was a large variability of LGS for beech and oak over the years. Prolonged growing season (LGS) of beech was statistically significant for 3 plots (Fondek, Borovec in Gorica) during the 2004 to 2011 period. For oak prolonged LGS was not statistically significant during the observation period