Alien species in local floras of the Voronezh Region Nature Reserve Fund (Russia)

The article deals with the analysis of alien species in local floras of the Voronezh region Nature Reserve Fund. The Voronezh Region is located on the border of the forest-steppe and steppe zones. 16 Model Protected Areas (PAs), having a different conservation status and a various size, have been chosen for the analysis. The article attempts to assess: a) the degree of biological contamination of PAs that protect forest-steppe and steppe ecosystems; b) features of the alien fractions of the PAs' flora of various categories. The characteristics of PAs with respect to the possibilities and conditions for the invasion of alien species of vascular plants are given. The alien fraction of the PAs' flora comprises 262 taxa: 255 species, 5 hybrids, 1 subspecies and 1 variety, referring to 178 genera and 66 families. For the typological analysis, alien species were divided into groups in accordance with the time of the invasion, the way of invasion and the naturalisation level. The average proportion of invasive species in PAs floras is 11.1% (in different local floras it varies from 4.4% to 16.8%). When considering stable flora elements only (excluding ephemerophytes and colonophytes), then the PAs' local flora contamination ratio will make the average of 6.1% (from 3.5% to 8.9%). The largest number of alien species is noted in the floras of state reserves and state nature sanctuaries, regional PAs are characterised by a smaller proportion of alien plants. The analysis of the ways of alien species' invasion has shown that human activity on introduction of plants makes an important contribution to the replenishment of the alien flora in protected areas: 31.7% of alien species had left the cultivation area, 15% were deliberately planted in the PAs. Transformer plants are of the greatest coenotic significance, out of 19 such alien species 11 are xenophytes, the other 8 species are ergasiophytes. The conclusion is made about the necessity to move from the monitoring of alien species to practical work on managing the process of alien plant invasion in state reserves