Features of the seasonal development of Juglans regia L. in the Right-bank Forest-Steppe of Ukraine

Abstract

The features of the seasonal development of Juglans regia L. in the conditions of the Right-bank Forest-Steppe during the 2019-2021 period were studied, recording fourphases and 17 subphases of the development of generative and vegetative organs. Trial plots were laid out in walnut plantations, shelterbelts and forest stands of walnut. The purpose of the study was to investigate the seasonal characteristics of the development of walnut varieties taking into account climate changes. During the establishment of the trial plots, the best areas for studies were selected based on the presence of at least 30 walnut specimens on them. During the phenological observations, the following phases of development were monitored: vegetative, flowering, fruiting, and completion of the vegetative phase. In this case, the dates of the beginning, mass onset and completion of the phenophase were recorded In the conditions of the Right-bank Forest-Steppe, Juglans regia stands are the first to start vegetative phase in the shelterbelts and forest plantations, and the onset of the same phenophases in forest phytocenoses occurs with a phenological interval of 12-14 days. This aspect may be due to the influence of agrotechnical conditions, soil and hydrological characteristics, microclimatic conditions and other factors that determine the development of woody plants in different ecosystems. The duration of the growing season in the territory of the Right-bank Forest-Steppe for walnut plantations is on average 183 days, and for forest conditions - 186 days. The walnut varieties 'Webu 6' and 'Efrem 1', grown in Vinnytsia region, have a shorter growing season compared to local, American, and European varieties and forms. The same is observed regarding growth and development – the experimental varieties begin to develop faster and complete growth earlier, which characterizes these varieties as quite winter-hardy. The results obtained also indicate a significant difference between the earliest and the latest dates of the onset of phenological phases in Juglans regia in the trial plots. This indicates the important genetic characteristics of this tree species, which determine the required time interval and the amount of effective temperatures for its normal development. The climatic conditions of the Right-bank Forest-Steppe are favorable for the mass cultivation of the 'Webu 6' and 'Efrem 1' walnut varieties. The phenological rhythms of the experimental varieties fully correspond to the duration of the growing season in the territory of the Right-bank Forest-Steppe. The onset of each vegetative phase is closely related to a genetically determined time interval, and the seasonal rhythms of the development of these varieties are a manifestation of their adaptation to the environment. This aspect is quite important, taking into account climatic changes, which can significantly affect the cultivation of walnut varieties. The phenological development of the varieties 'Webu 6' and 'Efrem 1' does not go beyond seasonal rhythms, therefore they are promising for use in the climatic conditions of the study region. In general, the varieties 'Webu 6' and 'Efrem 1' have significant prospects for widespread introduction in the conditions of the Right-bank Forest-Steppe. The results obtained make it possible to predict yields and improve methods for growing new varieties of walnut in this region.

Keywords

• juglans regia l.
• phenospectrum
• phenological phases
• seasonal rhythms
• vegetative organs
• generative organs
• growing season
• phenology amplitude