PHENOLOGICAL STATE OF protected WOODY plants in the circannian development cycle AT THE BEGINNING OF THE XXI CENTURY IN SAINT-PETERSBURG
The climate fluctuation in Saint-Petersburg is reflected in the dates of seasonal development of both native and introduced woody species, which influences the levels of their adaptation. There are positive trends of the average year temperature in sliding 5-years periods (1752-2013) and of vegetative season in geosystem (during the period 1841-2013: the minimum figure is 143 days in 1873-1877 and the maximum one is 194 days in 1988-1992). In the last 5-year period (2009-2013) this phonological interval has shortened to 177 days, which may be explained by the oscillation of the bioclimatic rhythm. In 2009-2012 the continental character of climate was more expressed. The period without frosts increased. Summer phonological stages came earlier and the autumnal events came later, especially what concerns the second part of autumn. The seasonal dynamics of nature in recent years was favorable for the growth and development of plants and for their preparing for winter. The majority of the species studied began their vegetation at the second phenological stage - «the revival of spring». Different species finished their vegetation at different phenological stages, and some species had the forced end of vegetation. The duration of vegetation varied from 133 days at Parthenocissus tricuspidata to 210 days at Genista tanaitica. As compared with the periods of a more cold and unfavorable climate, the amount of protected species capable to stand winter without frost damages has considerably increased. In recent years (2009-2012) the frost damages of shoots older than one year were observed only at 3 species (9%) among 32 deciduous species tested. The further warming of the climate may have negative influence on the hardiness of woody plants, especially the ones with a short period of winter rest.