Bud burst phenology in different poplar and willow clones

In the face of global climate changes, studies of bud burst and bud set phenology in trees are necessary to determine the duration of the growing season of plants, the optimal planting period, and seasonal works to achieve high productivity. The purpose of our study was to investigate bud burst phenology in different poplar and willow clones, what is important for predicting possible responses of woody plants to climate changes. Materials and methods: Bud burst phenology in poplar and willow was monitored both on the plants growing at experimental plot and on potted plants. Open-field plant research was conducted on a test site of fast-growing bioenergy trees in the M.M. Gryshko National Botanical Garden of NAS of Ukraine (Kyiv). Nine most productive poplar and willow clones were selected for the potted experiment. Throughout the growing season, the plants were kept outdoors, and after the seasonal fall of the leaves, the plants were transferred to an unheated storage room with a limited light regime. During spring, bud burst phenology was screened weekly through 45 days according to the 6-scores scale. The studies showed that the poplar plants grown under laboratory conditions demonstrated faster rates of bud burst compared to the willows, while the plants at the experimental plot, on the contrary, shown faster bud burst in the willows comparing to poplar clones. Such effects may be caused by the restricted light regime at the laboratory space what probably had stronger impact on the bud burst in willows, and in the case of open-field plants also by other random environmental factors. In potted conditions, willows demonstrated a tendency for faster flushing of lateral buds, while most poplar clones showed faster apical bud growth under the same conditions.