Ecological and Landscape Factors Affecting the Spread of European Mistletoe (Viscum album L.) in Urban Areas (A Case Study of the Kaliningrad City, Russia).

Liubov Skrypnik,Artem Pungin,Pavel Maslennikov,Nikolay Belov,Pavel Feduraev

doi:10.3390/plants9030394

Liubov Skrypnik, Artem Pungin + Show 3 more

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https://doi.org/10.3390/plants9030394

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Abstract

Green spaces are very important for an urban environment. Trees in cities develop under more stressful conditions and are, therefore, more susceptible to parasite including mistletoe infestation. The aim of this study was to investigate the ecological, microclimatic, and landscape factors causing the spread of European mistletoe (Viscum album L.) in urban conditions. The most numerous hosts of mistletoe were Tilia cordata (24.4%), Acer platanoides (22.7%), and Populus nigra (16.7%). On average, there were more than 10 mistletoe bushes per tree. The mass mistletoe infestations (more than 50 bushes per the tree) were detected for Populus × berolinensis, Populus nigra, and Acer saccharinum. The largest number of infected trees was detected in the green zone (city parks), historical housing estates, and green zone along water bodies. Based on the results of principal component analysis (PCA), the main factors causing the spread of mistletoe on the urban territories are trees’ age and relative air humidity. The factors reflecting environmental pollution (the content of heavy metals in the soil and the concentration of nitrogen dioxide in the air) did not statistically affect the mistletoe distribution in the study area. However, this result may be due to the heterogeneity of other parameters in the studied areas. Therefore, additional research is required to more accurately interpret the data on the relationship between environmental pollutions and distribution of mistletoe infestation of trees in urban areas.

Highlights

Urban green spaces have been increasingly recognized as key components of urban planning [1].The trees as urban keystone flora have a multitude of functions, such as to reduce air pollution, support biodiversity, mitigate heat island effects, increase land value, improve aesthetics, and even improve human health [2,3]
In the investigated area of Kaliningrad, over 43,000 mistletoe specimens were recorded on 3661 host trees
As a result of studies, no infected conifers were identified, which indicates the distribution of the subspecies Viscum album L. subsp

Summary

Introduction

The trees as urban keystone flora have a multitude of functions, such as to reduce air pollution, support biodiversity, mitigate heat island effects, increase land value, improve aesthetics, and even improve human health [2,3]. Under the influence of adverse environmental conditions, urban trees become more sensitive to biotic stressors (e.g., hemiparasitic plants, herbivorous insects, or pathogens). The hemiparasitic plants that infest trees and cause particular concern are mistletoes, which have been determined as one of the increasing agents of forest decline worldwide [5]. Most mistletoes are an evergreen plant that develops stable haustorium in the host tree. The plants assimilate their own carbon due to photosynthesis, which determines its green color, while completely

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