Fig. 2

Biplots from dimensions 1 and 2 (left) and 2 and 3 (right) from correspondence analysis: (a) Empirical (black) and USNVC classes (gray); (b) FIA (black) and USNVC classes (gray). Only the classes that loaded the highest on these dimensions are plotted in each case. Row standardization was used in these plots, and numbers in parentheses indicate the percentages of inertia explained by each dimension. Class names have been abbreviated to fit in some cases, and the full names of all classes can be found in Additional file 2