Table 4. Variance partitioning resulting from the partial canonical analyses of ecological and socioeconomical variables on species richness; data are for Tierra Colorada. Fraction of variation Proportion of variation F ratio df P Ecological (a + b) 0.510 5.27 3,26 0.004 Socioeconomical (b + c) 0.710 10.27 4,26 0.001 Total variation 0.811 8.12 9,26 0.001 Fraction decomposed   Ecol. not explained by soc. (a) 0.101 2.27 4,17 n.s. Soc. explained by ecol. (b) 0.409   Soc. not explained by ecol. (c) 0.301 5.42 5,17 0.01 Unexplained variation (d) 0.189 Notes: Three RDAs serve as the basis for the present table. The ecological variation (a + b) was obtained by RDA with ecological variables only, whereas the socioeconomical variation (b + c) was obtained by RDA with socioeconomical variables only. Total variation (a + b + c) was obtained by a joined RDA with ecological and socioeconomic variables. The fractions of variations are then decomposed arithmetically to isolate the effect of the strictly ecological and socioeconomical variation.