PHENOLOGICAL OBSERVATIONS OF AILANTHUS ALTISSIMA (MILL.) SWINGLE AT DIFFERENT URBAN AREAS

Introduction Invasive plants and animals are in the modern world very important issue. Invasive species were considered second, after the destruction of habitats, the direct reason for the reduction of biodiversity. It is believed that invasive alien species could cost the global economy up to 5 % of global GDP (Pimental et al., 1999). Statistically, 10 species introduced to cultivation of one “escapes” to grow one “escapes”. For 10 “fugitives” one bears fruit and reproduce. On 10 fruiting (naturalized) one is invasive. Invasive alien species are plants, animals, pathogens and other organisms that are not native to the ecosystem and may cause damage to the environment or the economy or adversely affect human health. In particular, invasive alien species have negative effects on biodiversity, including the reduction or elimination of populations of native species through competition, food, predation or transmission of pathogens and interfering with the functioning of ecosystems. Invasive alien species imported or spread outside their natural habitats, impact on native biodiversity nearly all ecosystems of the earth and are one of the biggest threats to this diversity. From the seventeenth century, invasive alien species have contributed inter alia to the extinction of almost 40 % of animal species and many species of plants. The problem of invasive alien species is constantly growing, mainly due to the expansion of global trade, transport and tourism, which may facilitate the introduction and spread of alien species in the environment. If for a given species new environment is sufficiently similar to the native, this species can survive and reproduce. Without encountering natural enemies or other restrictions species can become invasive: increase the area of its occurrence and displace native species. The damage increase further as a result of climate change, pollution, habitat loss and transforms environment by man. Species can “travel” different ways using different “natural” media. Alien species get into the environment through deliberate or accidental release into the environment of animals and plants grown at home or in home gardens. The most important sources of threat of biological diversity of introducted species are the plants, that after introduction into the wild nature reveal an ability to become established and spontaneous mastery and transformation of plant communities. The introduction of trees and shrubs is particular importance in this respect, because they can lead to long-term transformation of floristic composition and structure of forest and scrub phytocoenoses, especially if they are held for a long time, repeatedly and over large areas. A number of PHENOLOGICAL OBSERVATIONS OF AILANTHUS ALTISSIMA (MILL.) SWINGLE AT DIFFERENT URBAN AREAS


Introduction
Invasive plants and animals are in the modern world very important issue. Invasive species were considered second, after the destruction of habitats, the direct reason for the reduction of biodiversity. It is believed that invasive alien species could cost the global economy up to 5 % of global GDP (Pimental et al., 1999). Statistically, 10 species introduced to cultivation of one "escapes" to grow one "escapes". For 10 "fugitives" one bears fruit and reproduce. On 10 fruiting (naturalized) one is invasive.
Invasive alien species are plants, animals, pathogens and other organisms that are not native to the ecosystem and may cause damage to the environment or the economy or adversely affect human health. In particular, invasive alien species have negative effects on biodiversity, including the reduction or elimination of populations of native species through competition, food, predation or transmission of pathogens and interfering with the functioning of ecosystems. Invasive alien species imported or spread outside their natural habitats, impact on native biodiversity nearly all ecosystems of the earth and are one of the biggest threats to this diversity. From the seventeenth century, invasive alien species have contributed inter alia to the extinction of almost 40 % of animal species and many species of plants.
The problem of invasive alien species is constantly growing, mainly due to the expansion of global trade, transport and tourism, which may facilitate the introduction and spread of alien species in the environment. If for a given species new environment is sufficiently similar to the native, this species can survive and reproduce. Without encountering natural enemies or other restrictions species can become invasive: increase the area of its occurrence and displace native species. The damage increase further as a result of climate change, pollution, habitat loss and transforms environment by man. Species can "travel" different ways using different "natural" media. Alien species get into the environment through deliberate or accidental release into the environment of animals and plants grown at home or in home gardens.
The most important sources of threat of biological diversity of introducted species are the plants, that after introduction into the wild nature reveal an ability to become established and spontaneous mastery and transformation of plant communities. The introduction of trees and shrubs is particular importance in this respect, because they can lead to long-term transformation of floristic composition and structure of forest and scrub phytocoenoses, especially if they are held for a long time, repeatedly and over large areas. A number of Plants in Urban Areas and Landscape Slovak University of Agriculture in Nitra Faculty of Horticulture and Landscape Engineering species used in forestry and agriculture were introduced deliberately by man in order to increase productivity and competitiveness in the market (eg Quercus rubra) or has been planted as ornamental plants in gardens and parks (eg Acer negundo). Often, these species just got out of control they expand and even spread in invasive manner. An example of such tree species is Ailanthus altissima.

Material and method
Ailanthus altissima, commonly known as tree of heaven, ailanthus, or in Standard Chinese as chouchun (Chinese: 臭椿; pinyin: chòuchūn; it means "foul smelling tree"), is a deciduous tree in the Simaroubaceae family. It is native to both northeast and central China and Taiwan. The tree grows rapidly and is capable of reaching heights of 15 metres in 25 years. However, the species is also short lived and rarely lives more than 50 years. In China, the tree of heaven has a long and rich history. It was mentioned in the oldest extant Chinese dictionary and listed in countless Chinese medical texts for its purported ability to cure ailments ranging from mental illness to baldness (Hu, 1979). The roots, leaves and bark are still used today in traditional Chinese medicine, primarily as an astringent.
In addition to its use as an ornamental plant, the tree of heaven is also used for its wood, medicinal properties, and as a host plant to feed silkworms of the moth Samia cynthia, which produces silk that is stronger and cheaper than mulberry silk, although with inferior gloss and texture. It is also unable to take dye (Duke, 1983). This type of silk is known under various names: "pongee", "eri silk" and "Shantung silk". Its production is particularly well known in the Yantai region of that province (Gill, 2004).
The pale yellow, close-grained and satiny wood of Ailanthus altissima has been used in cabinet work. It is flexible and well suited to the manufacture of kitchen steamers, which are important in Chinese cuisine for cooking mantou, pastries and rice. It is also considered a good source of firewood across much of its range as it moderately hard and heavy, yet readily available. The wood is also used to make charcoal for culinary purposes (Barclay, 2013). Because the trees exhibit rapid growth for the first few years, the trunk has uneven texture between the inner and outer wood, which can cause the wood to twist or crack during drying. Although the live tree tends to have very flexible wood, the wood is quite hard once properly dried (Keeler, 1900).
In Europe, the plant first appeared in 1751. In Poland 1808 in the Cracow Botanical Garden (Seneta, 1991), and the status of this specie is domesticated anthropophyte.
It is typically a thermophilic species, because in many Polish cities is more and more areas.
Ailanthus alitissima may also appear in unusual places for its ecological optimum in the example of Warsaw. Nevertheless, from several years locations of Ailathus outside the city are recorded. An example of such a position are urban forests in the northern border city.
The aim of this paper is to demonstrate the presence of Ailanthus altissima in Warsaw at three different urban zones: centrum, districts located peripherally and suburban areas. Further aim of the study is to demonstrate the strength grade adaptations to environmental conditions (mainly thermal) expressed as phenoloical phases duration at Ailanthus altissima at different urban zones.
The work was made observations regarding the presence of Ailanthus altissima in Warsaw. Spot on the city reported the presence of the specimen in the lane NS and EW-striking in the central part of the city. Belts had a width of about 2 km. Belts stretched from the border of the suburb area in the north of the city to the suburban area to the south of Warsaw. Similarly, on the east-west direction.
The main research tool are phenological observations. Phenological observations were carried out on mature individuals. Observations took place in 2005-2011. They were a group of individuals in to the town center (highly urbanized zone), are outside the city center and suburban area. The description of the main phenophases are as follow: V -the growing phase (V1 -swelling and cracking buds; V2 -leaf stage; V3 -Phase fall leaves). Fl -flowering phase. Fr -fruiting phase (from fruit set to maturity).
The recorded duration of the given phases at each of the three locations were averaged and plotted.

Occurrence of Ailanthus alitissima in Warsaw
They allow us to conclude that plants growing in the central parts of the city have longer vegetation period and stronger growth. However, in locations situated on the outskirts of the city and urban forests growing period is shorter, and plants often remain in the form of shrubs.
As a result of the observation noted that Ailanthus altissima definitely prefers locations associated with the onset of the heat island phenomenon. Locations are primarily the central part of the city, with a high degree of urbanization. Very often, the trees appear in the cracks between sidewalks and buildings, the hardened surfaces (eg concrete slab). They form dense thickets through intensive sprawling root system. In the central part of Warsaw, covered by the observations we reported 97 groups or individual trees. Most positions formed a group in which one can distinguish some plants planted intentionally (eg, parks, squares and green street-adjacent) and a group of spontaneously proliferating plants. These spontaneously occurring specimens are developed in vegetative (root suckers) or generative (seeds) way.
Away from the city center Ailanthus altissima frequency of occurence decreases. There has been following number of grupus or individual trees of However, the most interesting is the presence of Ailanthus altissima in suburban zone, including forests within urban forests, such as the Mlociny Park north of Warsaw. As explained by phenological observations, the averaged results are presented in the form of charts, Ailanthus shows a certain, limited ability to adapt to growth in terms of less conducive thermal conditions.
Comparing the average duration of each phenological phases can be seen that the specimens growing in central parts of the city have increased the length of the vegetative and generative phases in relation to the other location. In case V2 phase difference between the copies of rising in the center of the city and suburban areas is up to 20 days. Similarly, the phase Fr -fruits in the center were formed earlier and ripened earlier than in the suburban area.
These observations show that the environmental conditions in the central parts of the city assisting the processes synanthropisation and confirm the thermal preferences of the species. However, do not preclude the adaptation of the species to a less comfortable thermal conditions. In the case of specimens growing in the outer parts of the city can be observed that the plants do not create the form of trees. Probably stronger frosts, especially those from the early autumn period and spring, which take place in Polish climatic conditions, effectively limit the growth of plants. As a result, the plants are retained on the stage of the shrubs.
It should be emphasized that the adverse thermal conditions for this species does not eliminate it, and do not constitute an obstacle to the self-renewal plants and independent distribution in terms natural or seminatural. The Ailanthus propagules are seeds, but the tree forms many root suckers, through which plants form dense clusters.
With the length of each phenological phases can draw a very important conclusion. Copies of growing in the center of the city start to vegetate earlier (this is a difference of up to about 7 to 10 days). Similarly, the end of the growing season -specimens growing in the suburban area of vegetation end about 14 earlier compared to specimens growing in the city center.
Currently on Polish territory is cultivated more than 2500 species (warieties no included) of trees and shrubs, what represents the number of about 10-fold higher than the number of native woody species. Relatively few of them so far revealed an ability to become established, Plants in Urban Areas and Landscape Slovak University of Agriculture in Nitra Faculty of Horticulture and Landscape Engineering but can not be ruled out that others in the future demonstrate such a property, because in the case of the above mentioned group of plants it can develop after several decades after the introduction. From the point of view of the diversity of local or regional alien species is always a real or potential threat to indigenous species: introduces new interactions in ecosystems, habitats is often acts reductively on native species, where it is often difficult to know in advance the degree of aggressiveness and ability to penetrate alien species into natural or semi-natural ecological systems (Olaczek, 2000). Such a phenomenon has been observed in the case of Ailanthus altissima. Ailanthus altissima is extremely competitive: producing up to 350 000 seeds per year, a very fast growing, drowning out other plants growing near, and even special producing toxins that prevent their development. Its root system is so strong that it can cause destruction of the foundations and sewers.
The process of synantropisation is especially intensive in urban areas. Due to the specific habitat conditions they are somewheat, difficult to accept by native vegetation, but acceptable to the species of foreign origin, recruiters from areas of similar habitat conditions for urbanareas, particularly in terms of heat. Interest in the flora of urban areas has been shown for almost 200 years (Jackowiak, 1998;Pyšek, 1989;Sudnik-Wójcikowska, 1998a). The species composition of urban vegetation and its function in the urban ecosystem as well as the role of man are significant because these factors affect ecological conditions and changes in urban areas.
In Warsaw tree-of-heaven, like in Wrocław, grew in a variety of habitats. The greatest number of its locations were found in quarters with high-rise and high-density residential areas, it means in central part of city, where the highes occurrence was recorded.
Downtown areas, they often grew in places associated with streets green areas, because Ailanthus tolerates soil salinity conditions. Tree of heaven grew also in industrial quarters, Ailanthus are especially often found in the vicinity of parks, which have been deliberately planted.
The vegetation of the city keeps undergoing transformation over time as a result of the changing ecological conditions.
The hemeroby structure of habitats where tree-ofheaven grows in Warsaw, Poznań or Wrocław agrees with data from Berlin, where the tree was also usually found in the same habitats (Kowarik and Böcker, 1984).
The center of a big city is warmer than the surrounding areas. There occurs the so -called urban thermal island. Its formation is controlled by a variety of factors, like the warming effect of buildings resulting from heat absorption during the day and its emission in the evening, additional heat emission sources generated by industry, and most importantly, the heating of houses. A consequence of the thermal island existence is the appearance of thermophilic plant species, i.e., with higher temperature requirements, and locally even an expansion of some of them. Those species include treeof-heaven, traveller's-joy (Czekalski and Kidawska, 2003) and buddleia (Kownas, 1958). The distribution of treeof-heaven in Warsaw, like in Wrocław in 1998-2001 concentrated in areas where air temperature was higher. Presumably the heat factor had a decisive influence on such a distribution, because tree-of-heaven has been shown to be a typical thermal indicator associated the warmest areas of Central European cities and highly industrialised regions, e.g., in Duisburg, Berlin, Leipzig, Halle and Zurich, as well as on the French coast of the Mediterranean and the Ruhr Basin in Germany (Kowarik, 1983a(Kowarik, , 1983bKowarik and Böcker, 1984;Kunick, 1984;Landolt, 1991aLandolt, , 1991bSudnik-Wójcikowska and Moraczewski, 1993;Sudnik-Wójcikowska, 1998a). In Poland data on distribution tree-of-heaven in urban areas were presented by Pacyniak (1976) and Sudnik-Wójcikowska (1998b) for Warsaw and Łódź.
However, in the last decade there apperance the Ailanthus outside the urban heat island. This may indicate Plants in Urban Areas and Landscape Slovak University of Agriculture in Nitra Faculty of Horticulture and Landscape Engineering either climate change, expressing a growing balance of thermal and systematic warming of the climate, as well as the adaptation of the species to less favorable thermal conditions. This phenomenon is extremely unfavorable, because the species is characterized by a large expansiveness, begins to appear in semi-natural and natural forest complexes. The Wrocław population of the tree-of-heaven, the largest in Poland, is probably associated with its introduction to Berlin in 1797 (Kowarik and Böcker, 1984). The tendency of population will increase Ailanthus can also be seen in other Polish cities, but the population from Wrocław of tree-of-heaven is excellent subject for studies on the biology, ecology and possible applications of treeof-heaven in urban areas. In Poland, it is recommended for planting along broad avenues and streets, and in squares and parks of western, central and southern Poland (Bugała et al., 1984). Its soil requirements are modest; it can grow in dry, low fertility, and trans-formed antropogenic soils with a high admixture of rubble. It often sows itself and regenerates in places where other plants are unable to grow. It displays an excellent ability to adapt, also to the difficult urban and industrial conditions continually changing under the human impact. Sukopp (1972) and Sudnik-Wójcikowska (1998a, 1998b) classified tree of heaven as a thermophilic species, i.e., growing the warmest areas in many Central European cities.

Conclusion
1. The central part of the city, with the associated heat island, represent the most advantageous place for selfgrowth plant, sow and create thickets by root suckers. This process each year is increasing and the trend is noticeable expansion of the population of Ailanthus. 2. The duration of the growing season of Ailanthus in the central part of the city comes to about 180 days. In the case of suburban areas, this period is reduced to about 150 days.