Bivariate correlation analysis between the appearance of the extremely small populations and the measured variables.

* Significant at the 5% level of probability, ** Significant at the 1% level of probability.
The numbers from 1 to 20 represent the 20 species with extremely small populations, as shown in Appendix S1. E1, canopy density; E2, altitude; E3, slope aspect; E5, road quality; E6, distance between population and road; E7, surrounding population density; E8, land use type.