ДОСЛІДЖЕННЯ ВПЛИВУ ОМЕЛИ БІЛОЇ (VISCUM ALBUM L.) НА ПРИРІСТ БІОМАСИ ДЕРЕВ (НА ПРИКЛАДІ ТОПОЛІ КАНАДСЬКОЇ, POPULUS DELTOIDES MOENCH.)

Abstract

Urban tree stands provide for key ecosystem services – productive, regulative and cultural. At the same time, they are negatively influenced by certain factors of anthropogenic (emissions from industries and traffic, application of de-icing salts) and biotic (infestation by the mistletoe species) origin. The White Mistletoe (Viscum album L.) is an evergreen hemiparasitic dwarf shrub with persistent haustoria. A dwarf’s diameter may reach up to 90 (120) cm, and the lifespan – over 45 years. A number of fruit-eating birds such as the Waxwing and the Mistle Thrush disperse this dwarf shrub. Mistletoe “seeds” survive the passage through the digestive tract of birds unharmed and are released with the faeces. Modern distribution range of the White Mistletoe in Europe extends from 10° W to 80° E and from about 35° S to 60° N. The limiting factor for the northern and eastern distribution of mistletoe is mean annual temperature. The Mistletoe is known to cause deterioration of tree health (i.e. trees infested by the White Mistletoe show increased defoliation and dieback, reduced growth and productivity) as well as aesthetic appearance. The aim of the study was to investigate the effects of the White Mistletoe’s (Viscum album L.) infestation on the Cottonwood’s (Populus deltoids Moench.) leaf area and biomass. Field survey was carried out in the city of Kharkiv, NE Ukraine. We measured total leaf area (cm2) and live biomass (g) of a sample of 25 randomly picked leaves from 20 annual branches infested by the Mistletoe and from 20 annual branches free of Mistletoe’s infestation collected from mature model Cottonwood trees in the roadside stands. The hypothesis of normal distribution of variables was tested with the Kolmogorov-Smirnov test (with the Lillefors’ correction) and the Shapiro-Wilk test etc. Hypothesis on the Mistletoe’s influence on the amount of Cottonwood’s photosynthetic tissues was tested with the Student’s t-criterion. Our results have shown that the White Mistletoe’s infestation may decrease the amount of assimilative tissues at the urban Cottonwood trees by ca. 20 %.