Environmental Preferences of an Invasive Plant Species, Bidens frondosa (Asteraceae), in European Russia and Western Siberia

To identify habitat conditions, indirect ordination methods on the basis of environmental scales are used widely in Europe. However, many alien plants are absent from those scales. Bidens frondosa (Asteraceae) is an invasive alien species distributed widely in Europe. It is becoming a significant part of natural plant communities, sometimes forming monospecific stands. This study aimed to empirically determine environmental factor values using analysis of the flora accompanying B. frondosa in 22 regions of European Russia collected in a 34-year time span. In European Russia, Tsyganov environmental scales are widely used for such analyses. We determined intervals of values for each environmental factor according to Tsyganov environmental scales, namely thermoclimatic scale (TM: 7.3–9.4), climate continentality (KN: 6.0–9.4), climate aridity/humidity (OM: 6.1–8.6), cryoclimatic scale (CR: 5.3–8.8), soil moisture (HD: 9.9–17.6), scale of the soil salt regimen (TR: 5.1–10.7), soil nitrogen availability (NT: 4.4–8.5), soil pH (RC: 4.8–8.8), habitat shading (LC: 2.0–4.5), and soil-moisture variability (FH: 0.7–5.9). These data on environmental factor values can be further used in ordination analyses of plant communities where B. frondosa appears in the subzone of coniferous-deciduous forests of Eastern Europe. Results of this study demonstrate the ecological preferences of this species and can be used to determine conditions of habitats invaded by B. frondosa.