Control Methods of Invasive Plant Species and the Influence of Cultural Vegetation on the Microclimate within the Central Wastewater Treatment Plant in Ostrava – Pilot Results

Abstract

This study is a pilot document focusing on two subjects. The first one concerns control methods of invasive plant species in the floodplain of the river Odra, specifically on wooded wetlands with pools. The second presents the influence of cultural vegetation on the microclimate within the Central Wastewater Treatment Plant in Ostrava (CWWTP). The problem is the spread of invasive plant species, especially the Canadian goldenrod (Solidago canadensis) and the Himalayan balsam (Impatiens glandulifera), which are expanding in the area to such an extent that they create monodominant invasive vegetation. Various methods of controlling invasive species were gradually tested in defined areas in the forested wetland. Both mechanical and chemical methods were used, as well as their combinations, to find out the most effective one. The process includes partial works, such as the selection of areas, the determination of diversity by using phytosociology, the subsequent application of selected interventions, and the monitoring of given invasive plants with growing accompanying species. This research is time-consuming; therefore, longer application, in terms of years, is assumed, which should lead to much more relevant results. The CWWTP area acts as a heated island, where surfaces are regularly overheated, negatively affecting the biota and the working environment. One of the working results will be the design of suitable vegetation composition, effectively reducing extreme surface temperatures, especially in summer. The determination of diversity is linked to this since any vegetation of different diversity can contribute to a favourable microclimate. An area inventory of tree and shrub vegetation and a phytosociological analysis of selected areas are used to evaluate diversity. These surveys were carried out in the wetland ecosystem and the CWWTP area. Another important step is the measurement of surface temperatures of cultural vegetation and built-up areas in the area of the CWWTP, which was carried out by remote sensing. Later, it will be possible to assess which of the existing biotopes contributes more and which less to the cooling function of the urban heat island and, at the same time, how to care for this vegetation so that it fulfills its role. In the article, we present the results of the pilot survey. For the control of the invasive species Impatiens glandulifera and Solidago canadensis, three control methods were chosen: mechanical (mowing), chemical (herbicide with the active ingredients of triclopyr and fluroxypyr (A.), and herbicide with pelargonic acid (B.)), and combined (A. + mowing, mowing + B.). The initial reactions of these plants to the interventions were visible after about 20–30 days. It was most pronounced in the area with the dead-end river branch with the combination of A. + mowing, where Impatiens glandulifera occurred, and then in the forest area with the occurrence of Solidago canadensis with the application of herbicide A. When measuring the surface temperatures of the cultural vegetation and built-up areas in the CWWTP area as a heat island, approximate temperatures were recorded: on average, the cultural vegetation ranged from 26.43 to 34.45 °C, the average temperature of the built-up areas was from 47.26 to 58.32 °C, and the water surfaces (CWWTP reservoirs) then around 20.65 °C. As part of the tree and shrub layer inventory, we recorded 17 tree species and 5 shrub species in the wetland ecosystem. The phytosociological analysis showed that due to the massive occurrence of invasive plants, the areas in the wetland ecosystem are poorer in species than the areas of the CWWTP with cultural vegetation.

Keywords: Community; Control methods; CWWTP Ostrava; Floodplain of the Odra River; Invasive plant species; Inventory; Microclimate; Ostrava; Urban heat island.