ANALYSIS OF SOLID WASTE LANDFILLS VEGETATION COVER OF KHARKIV REGION

Background. Determination of plant species diversity in the areas of solid waste landfills (hereinafter “landfills”) was carried out in order to identify patterns of vegetation cover and give an ecological assessment of the technocenosis. zones to 0.75 in similar zones. Cj calculated for two landfills equals 0.11. The plants were systematized by cenomorphic affiliation. The leading type of cenomorph for the flora of landfills is ruderal species (Ru); a significant share is occupied by forest plants (Sil), meadow (Pr) and steppe (St) plant species. Conclusions. Solid waste landfill sites are characterized by a high degree of transformation, which is clearly manifested in the vegetation formation patterns. The significant difference between the vegetation cover of landfill areas ( Сj = 0.11) indicates a low degree of similarity of species diversity due to the specifics of technogenesis of the studied ecosystems, historical landscape and preconditions for the formation of vegetation. Natural grass cover on the landfills is replaced by ruderal and shrub cover, which indicates harsh living conditions for cultivated plants and succession processes. There are three main patterns of the formarion of vegetation cover in the landfills: as a result of severe disturbances, indigenous plants are replaced by ruderants in the process of succession, while uncharacteristic species are introduced by biotic and abiotic factors.


INTRODUCTION
The number of man-made landscapes is growing rapidly, the areas occupied by solid waste (hereinafter "landfills"), which have a negative impact on the state of environmental components, including vegetation, need special attention.
The literature widely elucidates the possibilities of monitoring various components of the natural environment of landfills [6,7,19], which allows to respond in advance to the transformation of the natural environment, given the rapid response of plants as bioindicators. Numerous research works considered vegetation coverage peculiarities of landfills [3], its phytomeliorative properties [15,17,18,27], migration of plant species and formation of plant communities in landfills [9,16,24], as well as accumulation of pollutant abiotic components of the natural environment by plants and fungi in the territories of the landfills [14,20,25].
The aim of this work was to study the species diversity of flora, analyze the functions and properties of different groups of plants at Rohan and Derhachiv landfills in Kharkiv, and provide an ecological assessment of the state of technogenically transformed landscapes.

MATERIAL AND METHODS
The study of the vegetation cover of the landfills was conducted during the period of active vegetation (May-July 2020) on the territory of Kharkiv landfill sites (see Figure).
Rohan landfill is located on the southern border of Kharkiv. According to the geobotanical zoning, this area is located in the forest-steppe zone, in the valley of the Studenok River. The mesorelief of the landfill is represented by a beam, which is a remnant of a former tributary of the Studenok River, that indicates a small depth of groundwater. The landfill exhausted its functional significance in 1995, but it is still used. For more than two decades, succession processes have been taking place on the territory and an ecosystem with a specific flora is being formed there. Derhachiv landfill is located 15 km north of the city of Kharkiv in the valley of the river Lopan, on its left bank. The landfill is divided into separate functional zones -a new active landfill and an old one, reclaimed 20 years ago. The former landfill was laid 20 years ago and is now subject to backfilling and compaction for further reclamation [11]. The genesis of changes in the two studied landfills has some differences, primarily in the formation of flora.
Landfill vegetation cover was studied by method of geobotanical research. The main task was to identify general geobotanical characteristics of the territory and to determine the basic patterns of plant distribution relative to the landfill.

Derhachiv and Rohan landfills Дергачівський i Роганський полігони ТПВ
The area with vegetation cover near the SW landfill and on its territory was covered by linear routes method. The method of trial areas (10×10) was used for studying the floristic composition and determining the conditions of vegetation existence. According to the results of the study, a list of flora species was compiled with the subsequent determination of dominant representatives and the construction of associations by determinant [12].
Drude's method (1913) was used for quantitative counting of plants [2]. After taking into account the qualitative and quantitative composition of the vegetation cover, the dominant plant species were identified [2], coenomorphs according to O. Belgard were identified according to V. Tarasov [23]. To compare the floristic similarity of the studied areas, the floristic similarity coefficient of Jacquard was used [8]. To characterize the degree of succession, the types of cenomorphs for all species represented at Rohan and Derhachiv landfills were determined [23].

RESULTS AND DISCUSSION
It was found that the vegetation cover of Rohan landfill and the adjacent territories includes at least 92 species of higher vascular plants belonging to 34 families. 93 species belonging to 29 families were recorded at Derhachiv landfill. The leading families at both landfills were the families Asteraceae and Poaceae ( Table 1).
Analysis of life forms (according to Serebryakov) revealed the following: the vegetation cover of landfills includes herbaceous plants, trees, shrubberies, bushes and woody vines. The plants were grouped by life expectancy into perennial, annual and biennial species using the common method [21] ( Table 2). In the landfills, herbaceous perennials dominated, which indicates secondary succession processes in the formation of secondary vegetation on the transformed landscapes. The distribution of annual plant species indicates the primary formation of flora in the affected areas.
It was found that the vegetation cover is distributed unevenly on the territories of the landfills, therefore zoning of territories was carried out. Landfills in Kharkiv are charac terized by a sharp dismemberment and a high degree of technogenic transformation of landscapes, have their own clearly separated perimeter of the territory where waste is stored (operating landfill, hereinafter OL), active zone of unloa ding and compaction of waste, which is constantly changing in the process of waste accumulation (the epicenter of landfill, hereinafter EL). Areas that do not meet the standards over time and exhaust their acceptance function are subject to reclamation (reclaimed landfill, hereinafter RL). The areas adjacent to the landfills are characterized by linearly elongated forms of the landscape (dirt roads) directly adjacent to the landfill site on the one side and ruderal vegetation on the other, and form the ruderal landscape (R). Occasionally, there are small areas with relatively natural landscape features where grassy (NLG) or woody (NLW) vegetation predominantes.
Analysis of vegetation on the territory of Rohan and Derhachiv landfills revealed a certain difference in the species diversity of plants at landfills in accordance with the zoning of the territory ( Table 3).
The most pronounced species diversity of vegetation was found at Derhachiv landfill in the NLW zone (44.0 %), and at Rohan landfill -in the R zone (38.5 %). Asteraceae and Caprifoliaceae are the families whose representatives dominate the flora at both landfills. The heterogeneity of vegetation is obvious, which indicates the high level of transformation of active waste unloading areas -the impact of heavy machinery and waste. The dismemberment of the territory also sharply limits the species diversity in the OL and EL zones, where there is no vegetation. The area of active waste disposal (OL) is depleted of vegetation; similar tendencies occur along the perimeter of the landfill, where ruderal and semi-natural complexes are formed, which are dominated by numerous species of weeds and synanthropic plants. Asteraceae (I rank), Caprifoliaceae (II rank) and Brassicaceae (III rank) occupy the leading place among families. Representatives of other families are found in different areas with different frequency. Agropyron repens (L.) Gould, 1947), Erigeron annuus (L.) Pers., 1807), Lactuca serriola (L., 1756) and Acer negundo (L., 1753), Ulmus sp. (L.) dominate the vegetation in the NLW zone. Ruderal and other weed-field plants predominate in the R area, which is due to their ability to grow in clogged areas with high humidity. There is a clear tendency of substitution of annuals and biennials dominating in the areas under the impact of heavy machinery and active unloading (OL, EL, R) with perennial species in the "older" areas, which is the evidence of the formation of secondary successions and stable phytocenoses.
The analysis of vegetation cover showed that the greatest diversity of species was formed at Derhachiv landfill in the natural landscape area. At the same time, there is a tendency to suppress ruderal vegetation by aboriginal species, which indicates the potential for landscape restoration. The zone of ruderal landscape is dominated by ruderal vegetation, which indicates the primary succession processes. At the reclaimed landfill, the plants adapted to the drier conditions of the areas under anthropogenic transformation.
A comparison of vegetation cover within Rohan and Derhachiv landfills and between these two landfills was made and the significance of the difftrence was determined using Jacquard similarity coefficient Cj ( Table 4).
Comments: NLG -natural landscape features where grassy; NLW -natural landscape features where woody; R -ruderal landscape; OL -operating landfill; RL -reclaimed landfill. Comments here and in Table 4 Примітки: NLG -натуральний ландшафт, де переважає трав'яниста рослинність; NLW -натуральний ландшафт, де переважають дерева; R -рудеральний ландшафт; OL -епіцентр функціонування полігону (складування відходів); RL -рекультивований полігон. Примітки тут і в табл. 4 Table 4. From the data presented in Table 4, one can draw the following conclusions: research areas of Rohan landfill are characterized by significant similarity with Cj values from 0.75 to 0.59 points, indicating a high degree of vegetation similarity in the studied areas of the landfill; the flora throughout the landfill is rather homogeneous. In contrast, the studied areas of Derhachiv landfill are very heterogeneous and differ a lot in plant species composition (Cj varying from 0.18 to 0.48). The similarity coefficient Cj calculated for two landfills is 0.11. It illustrates a significant difference in the composition of flora, which is due to considerable differences in the formation of landfill ecosystemsthe age of landfills, specificity of land lying and usage, landscape historical background and floral genesis characteristic of Kharkiv region. However, the patterns in the vegetation formation of the disturbed landscapes can be traced quite clearly -a significant dismemberment of vegetation, abundance of ruderants in flora, peculiarities of flora formation in certain functional areas of landfills, etc.
Lepidium Densiflorum (Schrad., 1832) -an adventitious plant, which is not typical for the study area and Inula Helenium (L., 1753), which is under protection in Kharkiv region, were interesting floristic finds on the territory of Derhachiv landfill [13].
The study recorded an increasing presence of agricultural plants in the landfills that are widely used by humans (fruit and cultivated plants), as well as a small number of ornamental plant species, which, probably due to ornithochoria, found an atypical place of growth and adapted to it (Solidago canadensis (L., 1753), (a typical weed, widespread in the region), Fragaria vesca (L., 1753), Triticum durum (L. (1753), etc.). Some introduced species were registered on the territories of the landfills (OL and RL zones): Helianthus Annuus (L., 1753) and Triticum Durum. The study revealed an interesting fact about the phenological features of these species: the growing season significantly outstripped that of the plants growing under normal conditions. A similar fact was recorded in other scientific studies. This is due to an increased temperature regime in the active storage areas of the landfill, which are formed as a result of the humification process. Unfortunately, the proportion of phytomeliorants is extremely small (2.2 %), even smaller than the part of poisonous (2.7 %) and wild (6.9 %) species. To characterize the succession degree, a cenomorphic analysis of vegetation was performed ( Table 5) [23]. Some species are transitional. For example, stepant-pratant (StPr) is a meadow species that can grow in steppe conditions.
It was established that the species that are represented in the vegetation of Kharkiv landfills cover all types of cenomorphs. The leading type of cenomorph for the landfills flora is ruderal species (Ru), which is due to the significantly transformed landscapes in the active areas of landfill functioning where a secondary vegetation cover begins to form. A significant number of species are characteristic representatives of the forest (Sil), meadow (Pr) and steppe (St) plants. Such vegetation is typical of beam landscapes, in which landfills are laid according to standards. There are significantly fewer species of swamp (Pal), sand (Ps) and rock plants (Ptr). Thus, we can assume the existence of specific factors of the formation of such vegetation cover, whereby plants can be introduced due to ornithochoria, deflation, and surface runoff. Halophytes (Hal) and aquatic (Aq) species are the least abundant due to the atypical living conditions for such species, whereby soils are almost absent, highly degraded, poorly moistened and compressed. Comments: forest species -silvants (Sil); steppe species -stepants (St); meadow species -protanty (Pr); wetland species -paludants (Pal); plants of saline soils -halophytes (Hal); weeds -ruderants (Ru) Примітки: лісові види -сільванти (Sil); степові види -степанти (St), лучні види -пратанти (Pr); болотні види -палюданти (Pal); рослини засолених ґрунтів -галофіти (Hal); бур'яни -рудеранти (Ru)

CONCLUSIONS
Vegetation cover of landfills is represented by at least 117 plant species. The plant species composition is dominated by herbaceous and perennial species, which indicates the processes of secondary succession in the formation of vegetation cover. The plant species of the studied landfills were classified according to their practical use. It was establisheded that a significant proportion of the species are weeds, medicinal, or food plants. On the other hand, there is an extremely small number of phytomeliorants that are essential for the territories of devastated landscapes; this indicates the low potential for restoration of natural landscapes.
The territories of the landfills were significantly dismembered in the process of exploitation, therefore, the vegetation of different areas is different. The vegetation in the areas of active transportation and unloading of waste (OL) is represented by single ruderants, which indicates a high degree of territory damage, lack of fertile soil and primary succession signs. RL zones have a greater diversity of species, the leading families are Asteraceae and Caprifoliaceae, which in general are dominant families for both landfills. There is a tendency for secondary succession in these areas; ruderants are gradually being replaced by cultivated plants (ornithochorns from adjacent agrocenoses), perennials and shrubs. Similar trends are noticeable in the area of Derhachiv landfill, where the vegetation restoration has taken place for 20 years after reclamation. The NLW and NLG zones of both landfills were the most numerous by plant species. These territories are exposed to the least impact among other areas, and are formed independently. There is a significant dominance of perennials over ruderants and annuals, which indicates the potential for restoration of the natural landscape.