Geoecological analysis of the state of forest park plantations in the Dnipro city using Landsat satellite images

Abstract

The importance of the number and viability of green areas for creating a com- fortable and safe life for residents of urbanized areas is increasing with the growth of cities, which has not stopped since the first half of the 20th century. Dnipro is a city with progressive air pollution, therefore the effective use of its green areas in this aspect – the selection of tree species, regular assessment of their condition and timely response to changes in vegetative activity – becomes especially relevant. To solve the research task, a combination of on-site and remote methods of assessing the vital state of green areas of the city was chosen. First, spatial and statistical information about the city’s green areas was defined and summarized, and a cartographic and statistical base of raw data was created, potential anthropogenic factors of influence were determined, and reference areas were selected. At the second stage, a systematic survey and assessment of the vital state of the trees of selected areas was carried out for seven years: morphometric indicators of trees of certain species and assessment of the state of their morphological elements (roots, trunk, crown, leaves). According to the degree of damage, trees were classified as: healthy, weakened (damaged), severely weakened; dying and dead. At the third stage of the study, the correlation of the vital state indicator (Ln) and the normalized vegetation index (NDVI) was determined, based on images from Landsat sensors 8 and 9 of the L1 processing level, pre-processing of the images was performed using the SCP (Semi-automatic Classification Plugin) module integrated in QGIS. According to the results of on-site research, it was found that for the period 2015-2021, most parks and squares of the control group belong to the second category (weakened), three to the first (healthy) and one to the third (severely weakened). The main types of damage have been identified as well as species of trees that are most susceptible to damage. The dynamics of vegetation activity indicators reflect the general tendency to increase the vegetation cover of the city for six years. According to the results of the correlation analysis of NDVI and Ln values, a stable dependence between the index of vital state and the normalized vegetation index was revealed. The correlation between the specified indicators for each particular year is direct and varies from 0.5 to 0.9. The vital state of forest park plantations in Dnipro city is at a satisfactory level. The average Ln for the entire city is 65.6%. It was concluded that the exploitation of the gas-absorbing capacity of plants must be carried out in combination with technical measures in order to activate the processes of improving the environment.