The influence of short-term climate fluctuations on the reproductive capacity of woody plants in St. Petersburg

At the beginning of the 21st century in St. Petersburg, the number of species of trees and shrubs that have entered a reproductive state has noticeably increased. A number of them produced seed offspring for the first time over a long period of introduction. In such conditions, when the levels of adaptation change so noticeably and the biological characteristics of different plant species manifest themselves differently, the role and importance of conducting and processing long-term series of continuous phenological observations undoubtedly increases. During the period of continuous phenological monitoring (1980–2022) in the Botanical Garden of Peter the Great Komarov Botanical Institute Russian Academy of Sciences established that against the backdrop of climate warming in St. Petersburg, which began in the late 1980s, biological cyclicity, according to N. E. Bulygin, manifests itself in the alternation of early warm periods (1989, 1990, 1992, 1995, 2007, 2008, 2014, 2015, 2016, 2019, 2020, 2022) and late cold years (1980, 1982, 1985, 1987, 1996, 1998, 2003, 2004, 2006, 2011, 2012, 2013), which is reflected on the reproductive activity of woody plants and their ability to survive winter conditions. For the period 2001–2022 238 species entered the reproductive state, many of which had previously been in a vegetative state for decades. The improvement in the reproductive sphere of plants is especially noticeable after the abnormally warm winter of 2006/07; it intensified in 2015. This year and 2020 became the warmest during the period of instrumental meteorological observations in St. Petersburg. 50.8 % of cases of the first flowering and fruiting occur in early warm years; and only 16.4 % of cases – in late cold years. When summing up the results of introduction and assessing the prospects for breeding woody plants for urban floristics, it is necessary to take into account the cyclical climate of the region, the seasonal rhythm of plant development and their rhythm-adaptive connections.