Representation of introduced vegetation in pollen spectra of the Petrozavodsk State University Botanic Garden

Pollen analysis of aerial and subsurface spectra was carried out in different places in Petrozavodsk that is located in the Russian North-West: Botanic Garden of the Petrozavodsk State University and in some areas in Petrozavodsk (Klyuchevaya, Kukkovka, Drevlyanka, railway station and hotel «Severnaya») during 2019 and 2020. For this purpose, pollen traps were installed on the introducents (Sea-buckthorn (Hippophaё rhamnoides L.), Douglas fir (Pseudotsuga menziesii Franco), Manchurian walnut (Juglans mandschurica Maxim.), Siberian larch (Larix sibirica Ledeb.), European ash (Fraxinus excelsior L.), European white elm (Ulmus laevis Pall.), Northern red oak (Quercus rubra L.)) for two seasons to study the distance of pollen transportation and representation of surrounding plants in pollen spectra. Subsurface spectra were collected in the places of pollen traps installation and in the 10 km distance from the Botanic Garden, in the town. In two years, totally, 36 samples were studied. Materials from the pollen traps were treated according Erdtman acetolysis method and subsurface materials were treated according to Grichuk separation method. Arboreal pollen dominated (58–98%) in all spectra. Native species – pines (Pinus sp.), spruces (Picea sp.), birches (Betula sp.), alders (Alnus sp.), dominated in all spectra. Quantity of pollen of carried pollen traps plants varied in 2019 and 2020. Pollen of plants that grow at the border of their range – Small-leaved lime (Tilia cordata L.), Norway maple (Acer platanoides Mill.) were found mainly in the spectra collected in 2019. Introduced plants pollen contents differed in 2019 and 2020. Lilacs (Syringa sp.) pollen was found in spectra of both years. Pseudotsuga sp., yews (Taxaceae), Rhododendron sp., Hippophaё sp. pollen were found only in samples of the first year. Juglans sp. pollen was present only in five samples in 2019 and almost in all spectra in 2020. Quercus sp. pollen was present also only in five samples in 2019, but in three traps in 2020. Herbs were represented by pollen of the native taxa of grasses (Poaceae), asters (Asteraceae), sedges (Cyperaceae) in a small quantity (0.3-7.5%). Studied pollen spectra mainly reflect the regional vegetation features. Local floral components of the spectra were detected in the spectra in the immediate vicinity of them. Pollen of two or more introduced species was found in studied pollen spectra in small quantities. Spectra of the Botanic garden of the Petrozavodsk State University are typical for the spectra of the middle taiga. Differences of pollen spectra in different years could be caused by weather conditions and a number of other factors that are discussed like local vegetation state in these periods that affects on pollination and many others.