Climate warming determined changes of introduced conifer species bud swelling Phenophase, considering the aspect of hardiness zones in their natural habitats

Abstract

Many plant species across the globe had shifted their ranges or changed behaviours such as advanced bud burst, leaf unfolding, flowering, a delay in leaf colouring and fall, and consequently the extended duration of vegetation period due to changing climatic conditions. Changing climate may determine better adaptation of introduced species especially in boreal climate zones. Long term phenological observations (data for some species available starting since the 1956) of introduced species to Lithuania were carried out by dendrologists of Kaunas Botanical Garden of Vytautas Magnus University. Sequences of the start date of bud swelling phenophase of 11 introduced conifer species (Abies veitchii, Larix decidua, L. kaempferi, L. laricina, L. x marschlinsii, Larix sibirica, Larix sukaczewii, Picea mariana, Pinus mugo, Taxus baccata and Thuja occidentalis) were analyzed. Longest data sequences (1956–2016) were available for Larix decidua, L. kaempferi, L. laricina, L. sibirica, Pinus mugo and Taxus baccata. The start of bud swelling phenophase advanced on average from 10 (L. kaempferi) to 35 days (T. baccata) in 1956–2016, while the speed of changes was respectively from -0.17 to -0.59 days/year. Data sequences since 1980 were available for all 11 conifer species. In comparison to longer period (1956–2016), results from shorter period (1980–2016) show that changes of bud swelling phenophase were faster: the speed of changes for the same species in shorter period was -0.52 days/year (L. kaempferi) and -0.75 days/year (T. baccata). Most rapid changes in 1980–2016 period were estimated for Abies veitchii and Picea mariana (the speed of changes respectively was -0.98 and -0.92 days/year) and slowest – for Larix sibirica and L. sukaczewii (-0.10 and +0.12 days/year). The advance of bud swelling phenophase start date of introduced conifer species was most influenced by March temperature in Lithuania:[...]