Dynamics of the Seasonal Rhythm of Development of Some Species of the Genus Viburnum L. in the Changing Climate in the Southern Urals

Long-term data (2005–2020) from phenological observations of five species of the genus Viburnum from the collection of the South Ural Botanical Garden Institute, Ufa Federal Research Center, Russian Academy of Sciences (SUBGI UFRC RAS) (Viburnum opulus L., V. lantana L., V. dentatum L., V. veitchii C.H. Wright (V. glomeratum Maxim), and V. sargentii Koehne) have been analyzed. It is established that, in order to begin vegetation, these taxa need a sum of positive temperatures above 0°C (175–182°C), while the local species V. opulus begins to vegetate first. Positive temperatures from 235 to 278°C are required for the start of shoot growth and 436–691°C for the beginning of flowering. The North American species V. dentatum blooms later than all other species in the Bashkir Urals. Full lignification of shoots occurs earliest in V. dentatum at a total of positive temperatures of 2078°C, later than in V. lantana (2601°C), which can be explained by the geographical origin of these species. The Far Eastern species V. sargentii ends its vegetation earlier than all of the studied species, and the European V. sargentii ends its vegetation later than V. lantana; this is most likely due to the genetic characteristics of the species. The onset of the initial phases of seasonal development of Viburnum species (bud opening, the start of shoot growth, the beginning and end of flowering, and the beginning of lignification of shoots) is greatly influenced by the sum of positive temperatures above 0 and +5°C. At the beginning of the remaining phenophases (the end of shoot growth, full lignification, fruit ripening, and leaf fall), the influence of these temperature parameters, as well as the sum of temperatures above +10°C and the amount of precipitation, weakens. The duration of the growing season of species of the genus Viburnum in Ufa is 158–171 days. Over 16 years of observations, it is found that the timing of the beginning of vegetation, the beginning of flowering, and the end of vegetation in the local species V. opulus became later by 5–8 days; the process of shoot growth in this species lengthened by almost a month; and the lignification of shoots lengthened by 2 months. Such dynamics indicates a change in climatic conditions in the Republic of Bashkortostan.