Ecological and coenotic characteristic of Cyclachaena xanthiifolia (Nutt.) Fresen. In the flora of Ukraine

The flora of Ukraine includes Cyclachaena xanthiifolia adventitious species, which is dangerous for humans and animals. It got out of human control and spread widely throughout the whole territory, but its environmental features have not been studied enough. We found that Cyclachaena xanthiifolia is the eurytopic species in Ukraine, that is, it has wide ecological amplitude. It grows well and develops in wide weather and climatic divides: from semi-ombrophytic climate (1000 mm, Pre-Carpathian, Transcarpathia) to arid one (less than 350 mm, Prysyvashshia) in terms of climate humidity; from hemioceanic climate (Western Ukraine and the Black Sea coast) to subcontinental one (Dry-steppe and South-steppe zones) in terms of climate continentality. Its habitats are confined to flat, lowered, but well-drained and low areas. We did not find it at the altitudes of more than 500 m. This is heliophyte, a short-day plant. According to temperature requirements, it occupies an intermediate position between submesothermal and macrothermal plants that grow well when the amount of heat in April-October is from 1780 to 2620 kcal/cm2 and the sum of effective temperatures is from 2850 to 3750oC. When it comes to demand on soil moisture, it is predominantly mesophytic plant; with regard to soil solution reaction, it is neutrophilic or subacidophilic plant; with respect to soil fertility, it is eutrophic humifilous eunitrophilic plant on ruderal habitats, and oligotrophic agumyl or sub-agumyl heminitrophilic plant on technogenic ones. The highest frequency of occurrence, abundance and the best morphological plants’ parameters were found on black earth, chestnut, and meadow soils, and the worst plants’ parameters were found on sodpodzol, brown forest, sand, saline and bog soils. In relation to landscapes cultivation, this plant is euhemerobe or polyhemerobe. It grows in the Ambrosio artemisiifolia-Chenopodietum albi, Ambrosio artemisiifolia-Cirsietum setosi, Amaranto retroflexi-Setarietum glaucae, Amaranthetum blitoidi-Echinochloetum grusgalli, Poligono-Chenopodietea communities and others in segetal biotopes. It grows in the Ivaetum xanthiifoliae, Atriplicetum tataricae, Chenopodietum glauco-rubri, Chenopodio-Аtriplicetum hastatae, Ambrosio artemisiifoliae-Xanthietum strumariae communities and others in ruderal biotopes.


Introduction
The flora of Ukraine includes many adventitious plants.They appeared on the territory of the country as a result of international trade relations or the wildness of cultivated species.
These plants include Cyclachaena xanthiifolia (Nutt.)Fresen.North American species from the Asteraceae.It perfectly adapted to the new conditions of existence, got out of human control and by its uncontrolled spreading turned into a dangerous species for humans and animals.Until the 50-60s of the 20 th century, it was relatively rare ruderal species, and in the last 50-60s, it has become a common ruderal and segetal species (Kurdyukova, Zherdeva, 2014;Kurdyukova, Konoplia, 2012, 2018;Kurdyukova, 2019).
According to our and other surveys as of 1/1/2019, Cyclachaena xanthiifolia was found in all regions of Ukraine with the exception of alpine regions (over 500 m above sea level).
Minimum temperature for Cyclachaena xanthiifolia growth and development is considered to be 2-3 ºC, optimum temperature is 12-20ºC, and maximum temperature is 38 ºC.According to other sources, optimal conditions for seed germination and further growth were formed at a temperature of 12 to 22 ºC (Polenov, 1958;Fisyunov, 1984).
The purpose of our work is to give an ecological and coenotic assessment of Cyclachaena xanthiifolia in Ukraine.

Materials and methods
The studies were carried out during 2014-2018 in Ukraine.Ecological assessment of Cyclachaena xanthiifolia was carried out according to the scales adopted in the «Ecoflora of Ukraine» (Diduch, 2000).Coenotic confinedness was carried out on the basis of the processing of geobotanical and herbal descriptions, performed by us in the Northern and Southern steppe zones as well as Dry steppe and Forest steppe zones of Ukraine.Classification by confinedness to cenosis type was carried out according to A.D. Belgard (Belgard, 1950).

Results
In Ukraine, Cyclachaena xanthiifolia is a typical eurytopic species, that is, it has a wide ecological amplitude.It grows well and develops in wide weather and climatic divides: from semi-ombrophytic climate (1,000 mm, Pre-Carpathian, Transcarpathia) to arid one (less than 350 mm, Prysyvashshia) in terms of climate humidity; from hemioceanic climate (Western Ukraine and the Black Sea coast) to subcontinental one (Dry-steppe and South-steppe zones) in terms of climate continentality, as well as on a wide variety of substrates (from high-fertile well-provided with humus to very poor undeveloped soils without humus layer).Its habitats are confined to flat, lowered, but well-drained and low areas (up to 500 m above sea level).We did not find it at the altitudes of more than 500 m.This is a short-day plant, some kind of heliophyte, that is, it grows mainly in open places.
Cyclachaena xanthiifolia often formed homotypical thickets there, and withstood shading of up to 40% of full light in crops, gardens, parks as well as along fences.
According to temperature requirements, Cyclachaena xanthiifolia occupies an intermediate position between submesothermal and macrothermal plants that grow well when the amount of heat for April-October is from 1780 to 2620 kcal/cm 2 and the sum of effective temperatures is from 2850 to 3750 ºC.
The relationship between biomorphological parameters of Cyclachaena xanthiifolia plants and physicochemical properties of various soil types was fairly clear.According to generalized data, the highest frequency of occurrence, abundance and best morphological plants' parameters were found on black earth, chestnut, and meadow soils, and the worst plants' parameters were found on sod-podzol, brown forest, sand, saline and bog soils.In general, it showed signs of eutrophic humifilous eunitrophilic species in the crops of cultivated plants and typical ruderal habitats, and oligotrophic agumyl or sub-agumyl heminitrophilic species on technogenic ones.
According to soil solution reaction, Cyclachaena xanthiifolia is neutrophil or subacidophilic plant, as it prefers neutral or slightly acidic soils with pH interval from 6,5 to 7,1.
When it comes to demand on soil moisture, Cyclachaena xanthiifolia is predominantly mesophytic plant.The optimal conditions for its growth and development took shape at a moisture content of soil meter layer at the level of 70-80% of HB.At the same time, it tolerated its temporary decrease to 40-60% of HB, which indicates a flexible mechanism of adaptation to dry conditions and explains a high frequency of occurrence and abundance in areas of unstable and insufficient moisture.
According to soil moisture variability over the course of a year, Cyclachaena xanthiifolia belongs to hemihydro-contrast-phylous plants of the eurytopic type confined to ecotopes with moderately uneven wetting of the root layer with moderate or slight wetting by its sediments and melt water.
The high anthropotolerance of Cyclachaena xanthiifolia and the ability to survive in modern conditions are indicated by the anthropogenic ecosystems wherein it is common.Being a kenophyte (introduced to Ukraine in 1840), Cyclachaena xanthiifolia has long been naturalized and is now persistently distributed in all anthropogenic ecosystems (epecophyte), including urbanized ones, where it forms euhemerobic and polyhemerobic communities.
The maximum abundance, projective cover, biomass and seed productivity of Cyclachaena xanthiifolia were formed in the territories of manure storages, landfills, livestock farms, as well as along summer livestock camps and alluvial soils along river banks.These indicators were somewhat worse for plants growing in orchards, vegetable gardens, crops of melons and gourds, as well as vegetables and row crops; and minimal indicators were shown at construction and industrial sites, quarries, railway and automobile embankments, pastures, etc. (Table 1).

Conclusions
Cyclachaena xanthiifolia plants are characterized by wide ecological amplitude.It grows in different conditions: from semiombrophytic climate to arid one, and from hemioceanic climate to subcontinental one.In terms of altitude distribution, it is predominantly flat species.When it comes to demand on heat, it is submesotherm or macrotherm plant.
When it comes to demand on soil moisture, it is predominantly mesophytic plant; with regard to soil solution reaction, it is neutrophilic or subacidophilic plant; with respect to soil fertility, it is eutrophic humifilous eunitrophilic plant on ruderal habitats, and oligotrophic agumyl or sub-agumyl heminitrophilic plant on technogenic ones.
Cyclachaena xanthiifolia is spreading in all anthropogenic ecosystems.In relation to landscapes cultivation, this plant is euhemerobe or polyhemerobe.

Table 1 .
Morphobiological indicators of Cyclachaena xanthiifolia in various environmental conditions of growth and