Yavnyi M. Forests and Sanitary State of the Elm Stands of Kyiv Polissya and Their Rehabilitation

The thesis is devoted to research of forests and sanitary state of the elm species of Kyiv Polissya Region and their improvement. A focus is made on the global scale of the elm trees degradation and massive drying which are registered in Ukraine and the world. Analysis of population changes according to the occupancy areas development stages revealed that the studied plantations were in a state of spreading or so-called crisis in the dynamics from 2004 to 2006 and in a state of explosion since 2007. The existing areas of the majority of trunk pests are characterized by high, medium and low attack rate. We should note that chronic occupancy areas are characterized by the long period of existence, the relatively low, although elevated (in comparison with healthy plantings) number of insects and amount of the current dead trees. The occasional areas of occupancy are characterized by the relatively short (3–5 years) development period, the high number and volume of the current dead trees. In both cases, the reversible and irreversible reactions of forest stands are possible, although in the second case the full destruction of the planting is often observed under condition of mass reproduction. Near the areas of mass reproduction, which are characterized by excessive population density, usually there are migration centers where insects settle in search of new habitats.