Phenological multivariance of Betula pendula Roth in an anthropogenically transformed environment

Abstract The article presents the results of long-term biomonitoring based on the phenology of the arboreal species Betula pendula of the city of Yoshkar-Ola, Russia. The phenological multivariance of B. pendula was studied for the first time at different stages of the ontogenesis of the generative period, in the gradient of atmospheric air pollution by industrial and automotive toxicants. The rhythm of seasonal development of B. pendula depends on both individual and age characteristics, as well as on the influence of conditions of a specific urban microclimate and environmental pollution. Middle-aged generative individuals of B. pendula are characterized by earlier periods of the onset of phenophases, rapid leaf unfolding, prolonged flowering, yellowing of leaves and, in general, the growing season, compared with young and old generative trees. The asynchrony of seasonal development is characteristic mainly for trees located in the zone of medium pollution. Under conditions of a specific microclimate and air pollution, heterogeneity within ontogenetic groups B. pendula increases. The adaptation of B. pendula individuals to adverse weather factors and urban conditions is determined by the diversity of phenorhythmogroups in the generative period of ontogenesis.