To ecological safety of green plantations under the rapid invasion of the white mistletoe (Viscum Album L.)

A short description of the issue. Environmental factors that contribute to the rapid spread of the White Mistletoe (Viscum album L.) have been investigated for increase in the level of the ecological safety of green plantations. The White Mistletoe is an evergreen hemiparasitic dwarf shrub with persistent haustoria. A dwarf’s diameter may reach up to 90 (100) cm, and the lifespan – over 40 years. 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. 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. Nowadays due to global climate change the range of the White Mistletoe’s distribution is expanding both northward by latitude and upward by altitude in mountain areas. In many cities of Ukraine the White Mistletoe has been a common and widely distributed species. The aim of the study is to determine the relationship between the White Mistletoe density and environmental factors in urban landscapes to provide the ecological safety of green plantations. Materials and methods. Field surveys were carried out in the city of Kharkiv (Ukraine). Sample plots were located within north, northeast, central, west and southeast parts of the city. We used semi-quantitative indexes as a proxy of the White Mistletoe abundance at individual infested tree as follows: "1" was assigned for the range of the Mistletoe individual dwarves from 1 to 5, "2" – from 6 to 10, "3" – from 11 to 20, "4" – from 21 to 40, etc. For determination of the White Mistletoe populations’ age structure we established three age classes determined visually. When the White Mistletoe did not produce fruits and its diameter was from 0 to 25 cm, the plant was considered as «juvenile», for the plants with flowers or fruits and diameter from 25 to 50 cm the «generative» age class was assigned, and the shrubs with diameters over 51 cm were considered as "senile". Depending on the actual age structure of local populations their population trends ("stable", "growing", "declining") were established. The principal component analysis was conducted in order to determine relationships between The White Mistletoe density and landscape characteristics. Research results. With the use of principal component analysis environmental variables which influence rapid spread of the White Mistletoe on the level of landscape were evaluated. The White Mistletoe depending prevailing shares of the White Mistletoe hosts: White Willow, Norway Maple, Silver Maple, Robinia Pseudoacacia, Balsamic Poplar and Black Poplar and Garden Apple. Research results should be considered when developing and reconstructing gardening in cities Eastern Forest-Steppe of Ukraine. Further research should be directed to the developing of environmentally sound recommendations on the White Mistletoe population management in urban ecosystems. Acknowledgements. The author sincerely acknowledges Mr Yuri Vergeles (O. M. Beketov NUUEK) for invaluable assistance in consultations and practical recommendations on the collection and systematization of research material and participation in some field observations