Relations of the species wealth of adventive and aboriginal fractions of floras with the characteristics of climate and relief in the Middle Volga region

Overall, 34 local floras of vascular plants were analyzed at testing sites in the Middle Volga region with an area of 400 km2. Noticeable differences were revealed in the nature of correlations between the number of species of adventitious and native flora fractions and environmental factors: climate and relief. In the region, the number of native species is negatively related to air temperature, evaporation rates, and water deficit, while adventive species show a positive relationship with these characteristics. Adventive species are more often found in gently sloping lowlands in polygons characterized by increased elevation differences and drainage area. In general, adventitious species are more associated with semi-arid conditions in sites with relatively high ranges of environmental factors and standard deviation. Multiple regression showed that adventive species are more closely related to environmental factors than native species. In the region, adventive species are distributed predominantly in places (ecotopes) with increased environmental heterogeneity. An analysis of the relationships with environmental factors of the studied fractions may indicate that their distribution on the test sites is consistent, as a result of which they do not show opposition, which is also confirmed by the weak positive relationship between the richness of their species.